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Insights into the Acadian orogeny, New England Appalachians: a provenance study of the Carrabassett and Kittery formations, Maine.

ABSTRACT

The Central Maine Basin anal Merrimack Trough are Silurian basins that formed adjacent to or were accreted to the Laurentian margin during the Acadian orogeny. The Early Devonian Carrabassett Formation of the Central Maine Basin and the Kittery Formation of the Merrimack Trough have major and trace element compositions indicative of a passive continental margin provenance, not unlike the older formations of the Central Maine Basin that are thought to have been derived from Laurentian sources. However, both the Carrabassett and Kittery formations have paleocurrent indicators of outboard sources. The Carrabassett Formation is one of the youngest formations of the Central Maine Basin and was deposited just prior to the Acadian orogeny. The Carrabassett and Kittery formations have major and trace element concentrations suggestive of passive margin turbidites derived from intermediate to felsic sources, inconsistent with a juvenile Avalonian provenance. The Carrabassett Formation contains detrital zircon grains that match the ages of peri-Gondwanan Ganderia. Unlike the dominance of positive bulk-rock [[epsilon].sub.Nd] values that are characteristic of Avalonia, Ganderia has negative [[epsilon].sub.Nd] values that are a better match for the negative [[epsilon].sub.Nd] values of the Carrabassett and Kittery formations. However, Ganderia accreted to Laurentia during the Salinic orogeny, prior to the deposition of the Carrabassett Formation, and was basement to the sediments of the Central Maine Basin upon which the Carrabassett and other formations were deposited. Wedging of Ganderia by Avalonia during the initial stages of the Acadian orogeny may have uplifted Ganderia, forming highlands outboard of the Central Maine Basin that served as the source of the Carrabassett Formation sediments.

RESUME

Le bassin central du Maine et la cuvette de Merrimack constituent des bassins siluriens s'etant formes le long de la marge laurentienne ou s'y etant accretes au cours de l'orogenese acadienne. La Formation du Devonien precoce de Carrabassett, dans le bassin central du Maine, et la Formation de Kittery, de la cuvette de Merrimack, presentent des compositions en elements majeurs et traces signalant une provenance d'une marge continentale passive, a l'instar des formations plus agees du bassin central du Maine qu'on pense originaires de sources laurentiennes. Les formations de Carrabassett et de Kittery comportem toutefois des indicateurs de paleocourants de sources exterieures. La Formation de Carrabassett constitue l'une des formations les plus recentes du bassin central du Maine; elle s'est mise en place juste avant l'orogenese acadienne. Les caracteristiques geochimiques et geochronologique des formations de Carrabassett et de Kittery pourraient par consequent permettre l'identification du terrane de collision. Les formations de Carrabassett et de Kittery possedent des concentrations d'elements majeurs et traces evoquant les turbidites de marge passive en provenance de sources intermediaires a felsiques, ce qui est contradictoire avec une origine avalonienne juvenile. La Formation de Carrabassett comporte des grains detritiques de zircon correspondant aux ages du Ganderia perigondwanien. Contrairement a la predominance de concentrations [[epsilon].sub.Nd] positives de roche en vrac caracteristiques d'Avalonia, Ganderia presentent des concentrations [[epsilon].sub.Nd] negatives qui cadrent mieux avec les concentrations [[epsilon].sub.Nd] negatives des formations de Carrabassett et de Kittery. Ganderia s'est toutefois accrete a Laurentia au cours de l'orogenese salinique, avant le depot de la Formation de Carrabassett, et il a constitue le socle des sediments du bassin central du Maine sur lesquels Carrabassett et d'autres formations se sont deposees. L'enfoncement d'Avalonia sous Ganderia au cours des stades initiaux de l'orogenese acadienne pourrait avoir souleve Ganderia, formant un massifa l'exterieur du bassin central du Maine qui a servi de source aux sediments de la Formation de Carrabassett.

[Traduit par la redaction]

INTRODUCTION

More studies have been conducted of and more has been written about the Acadian orogeny than any other New England orogenic event (e.g., Osberg et al. 1989; Roy and Skehan 1993; Rankin 1994; Bradley et al. 2000; Eusden et al. 2000; Tucker et al. 2001 and references therein). In spite of this volume of work, the fundamental problem of what caused the et al.ngland part of the Acadian orogeny remains.

The orogenies of the New England Appalachians resulted from the collision of several microcontinents to the Laurentian margin. In the context of this study, the most significant microcontinents are Ganderia and Avalonia. From the early to middle Paleozoic, the Laurentian margin progressively expanded due to the accretion of these microcontinents. They represent two separate peri-Gondwanan blocks that had separate but similar Neoproterozoic histories but were distinct from the Early Paleozoic (van Staal 2007). Ganderia was a Late Neoproterozoic to Early Cambrian arc terrane that rifted off Amazonia at about 505 Ma whereas Avalonia, a largely juvenile arc unconformably covered by Cambrian-Ordovician platform sediments, probably rifted from Gondwana ~30 million years later (van Staal 2007). The Salinic orogeny was caused by collision of the Ganderian margin and Laurentian at ~430-422 Ma. Many geologists think that the subsequent collision of Avalonia with composite Laurentia at ~420-400 Ma caused the Acadian orogeny (e.g., Osberg et al. 1989; Robinson et al. 1998), but lack of evidence of Acadian metamorphism in the New England part of Avalonia (Fig. 1) is a challenge to this interpretation (Walsh et al. 2007; Aleinikoff et al. 2007). Instead, the geochronology of Avalonia and inboard peri-Gondwanan terranes document a Pennsylvanian-Late Permian orogenic event (Eusden and Barreiro 1988; Spear and Harrison 1989; Tucker and Robinson 1990; Dallmeyer and Takasu 1992; Wintsch et al. 1992; Getty and Gromet 1992; West 1993; Lux and West 1993; Walsh et al. 2007).

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West and north of the New England Avalonia are the peri-Gondwanan Willimantic and Pelham domes and the Massabesic Gneiss Complex (Fig. 1). In common with Avalonia, no Acadian metamophic or igneous ages have been identified in the Willimantic or the Pelham domes. Both domes contain orthogneisses with ages of ~620 Ma, a common age of peri-Gondwanan rocks, with a strong overprinting of a ~280 Ma event in the Alleghanian. As acknowledged by Robinson et al. (1998), this lack of Ordovician-Devonian igneous activity and Silurian-Devonian metamorphism is inconsistent with the assignment of these domes to a peri-Gondwanan terrane that collided with Laurentia prior to the Alleghanian. For these reasons, some workers think that Avalonia did not arrive in southern New England until the Alleghanian orogeny (Zartman and Naylor 1984; Wintsch and Sutter 1986; Mosher et al. 1993; Wintsch et al. 1993; Rankin 1994; Walsh et al. 2007) and may have been emplaced along strike-slip faults in the Late Paleozoic (Robinson et al. 1998). Alternatively, Wintsch et al. (1992) suggested that the portion of Avalonia that collided during the Acadian was subsequently thrust further under the allochthonous rocks of the Central Maine Basin, Merrimack Trough, and Putnam-Nashoba terrane during the Alleghanian orogeny and is no longer exposed to provide evidence of Avalonian involvement with the Acadian event.

The Massabesic Gneiss complex shares the same ~620 and 280 Ma events with Avalonia of southeastern New England (Aleinikoff et al. 1979), and is the only peri-Gondwanan inlier that may preserve evidence of the Acadian orogeny. This gneiss contains amphibolite and an attenuated granitic dike with ~400 Ma zircon and monazite, respectively (Aleinikoff et al. 1995). The possibility that the Massabesic Gneiss Complex is of Ganderian affinity (Moench and Alienikoff 2003; Dorais et al. 2007) suggests that the complex had docked with Laurentia in the Salinic orogeny and, rather than having been the Acadian colliding terrane, it was on the receiving [[epsilon].sub.Nd] of Avalonia's collision during the Acadian. Thus the question remains: What lithotectonic elements collided with Laurentia in this part of the New England Appalachians to cause the Acadian orogeny?

A Silurian to Early Devonian basin called the Central Maine Basin developed between Laurentia and the approaching terrane that docked to cause the Acadian orogeny. The earliest sediments deposited in the Central Maine Basin were derived from Laurentia whereas the uppermost formations preserve paleocurrent indicators from the east, suggesting an outboard source thought to be Avalonia (Hanson and Bradley 1989; Hanson et al. 1993; Bradley and Hanson 2002). Because sediments carry the major and trace element, isotopic, and detrital zircon signatures of their source rocks (O'Nions et al. 1983; Allegre and Rousseau 1984; Michard et al. 1985; McLennan et al. 1990; Gleason et al. 1994; Anderson and Sampson 1995; Bock et al. 1998; Wintsch et al. 2007), we undertook this study to determine whether or not the bulk-rock geochemical characteristics and detrital zircon geochronology of easterly derived sediments, i.e., the Carrabassett Formation of Maine, would identify the outboard terrane that collided with Laurentia. We compare these geochemical and geochronological parameters with those of the older formations of the Central Maine Basin in order to make comparisons between the source regions of sediments shed from Laurentia and outboard sources.

The Silurian Merrimack Trough lies to the east, outboard of the Central Maine Basin (Fig.1). This terrane is also an enigmatic belt that has traditionally been interpreted as peri-Gondwanan (e.g., Hibbard et al. 2006). Like the Carrabassett Formation of the Central Maine Basin, the Kittery Formation of the Merrimack Trough has paleocurrent indicators of an easterly source (Rickerich 1983). We also compare the bulkrock geochemical, isotopic, and detrital zircon characteristics of the Kittery Formation with those of the Carrabassett Formation in order to evaluate provenance characteristics of the approaching Acadian colliding element.

GEOLOGIC SETTING

Central Maine Basin

The formations of the Central Maine Basin (Fig. 1) have been given different names by various workers depending on the region of study, but because we concentrated on the formations of western Maine, we use the names established by Moench and co-workers (e.g., Moench and Pankiwskyj 1988). We specifically focused on the Silurian and Devonian rocks of the Central Maine Basin which span a time frame from significantly before to just prior to and perhaps concurrent with the initial deformation of the Acadian orogeny (Bradley and Hanson 2002). From oldest to youngest, the formations of interest are the Rangeley, Perry Mountain, Smalls Falls, Madrid, and Carrabassett.

These formations are draped across what has been called a tectonic hinge that coincides with the eastern margin of the Bronson Hill anticlinorium (Fig. 1; Hatch et al. 1983). Northwest of the hinge, the sediments were deposited on a narrow shelf and lie unconformably on pre-Silurian rocks. Southeast of the hinge, the metasedimentary rocks thicken, representing the site of the Central Maine depositional basin. The hinge line appears to have been an active tectonic feature that controlled sedimentation from early Silurian to the culmination of the Acadian orogeny. The direction from which these sediments were derived is crucial to our study. An easterly or southeasterly transport direction is suggestive of Laurentian provenance. In contrast, westerly transportation directions have been interpreted as favoring a peri-Gondwanan source (Bradley and Hanson 2002).

The Rangeley Formation consists of three members, A, B, and C (Moench and Pankiwskyj 1988). Parts A and B thicken by an order of magnitude across the tectonic hinge to the southeast. Part A consists of a large sheet of marine sandstone and conglomerate, approximately 1200 m thick in the Rangeley quadrangle in Maine. The conglomerate includes boulders of the distinctive Ordovician Attean Quartz Monzonite from the Boundary Mountain anticlinorium to the northwest. Limited paleocurrent data suggest that the Perry Mountain and Smalls Falls formations were also derived from a source to the northwest (Hanson et al. 1993; Bradley and Hanson 2002). Interbedded quartzose sandstone and shale of the Perry Mountain Formation coarsen upward and to the northwest, also indicating a source from the northwest. Higher in the Silurian rocks of the Central Maine Basin, paleocurrent indicators indicate a non-western source area (Moench and Boudette 1970; Ludman and Griffin 1974; Ludman 1976; Bradley and Hanson 1989, 2002). Three observations indicate transportation and perhaps derivation of the Madrid Formation from the northeast (Hanson et al. 1993): (1) southeasterly paleocurrent indicators, (2) decreasing ratio of facies B to facies D turbidites to the southwest, and (3) thinning of the Madrid Formation to the southwest.

The Carrabassett Formation, correlative with the Littleton Formation of New Hampshire (Moench and Pankiwskyj 1988; Hatch and Moench 1984), is the youngest, most widespread pre-Acadian formation of the Central Maine Basin. It was deposited just prior to the onset of Acadian deformation and consists of ~2000 m of Early Devonian, mud-rich turbidites that are locally metamorphosed to the chlorite zone of the greenschist facies (Hanson et al. 1993). Several facies are identified, from massive sandstones, undifferentiated thin to thick-bedded turbidites, chaotic facies, and thick-bedded turbidites to thin-bedded turbidites. The chaotic strata are considered to be olistrostromes. Coarse sandstone and conglomerate are absent. Paleocurrent data show a dominant flow from the southeast. Bradley and Hanson (2002) concluded that the combination of these facies and paleocurrent indicators reveals that the sediments were deposited on a submarine slope that descended to the northwest in the Central Maine depositional basin. High sedimentation rates, coupled with earthquakes from early Acadian tectonic disturbances, led to large amounts of sediment being remobilized and deposited as slumps and debris flows. As such, the Carrabassett Formation would represent deposition during the demise of the deep-water Central Maine Basin as it closed during the initial stages of Acadian collision.

Merrimack Trough

The Merrimack Trough is almost 400 km long, extending from Maine and southeastern New Hampshire through Massachusetts almost to Long Island Sound (Fig.1). In New Hampshire, it is in fault contact with the Massabesic Gneiss Complex on the northwest and with the Rye Complex on the southeast. It was originally defined by Katz (1917) to consist of the Kittery, Eliot, and Berwick formations that constitute a thick sequence of calcareous turbidites in the New Hampshire and Maine (Katz 1917; Billings 1956; Bothner et al. 1984; Bothner and Hussey 1999). Recently, Wintsch et al. (2007) concluded from detrital zircon geochronology that the Berwick Formation was Silurian and Laurentia-derived, whereas the Kittery Formation (middle Ordovician or younger), with its paleocurrent indicators of an eastern source and different detrital zircon signatures, is peri-Gondwanan. They interpreted the fault that separates the Berwick Formation from the Kittery and Eliot formations as a thrust fault that placed the Laurentiaderived Berwick on top of the peri-Gondwana-derived Kittery and Eliot. Thus it is particularly interesting to compare the provenance signature of the Carrabassett Formation with that of the Kittery Formation, as both appear to have an outboard provenance and have the potential to yield information about the Acadian colliding terrane.

SAMPLE LOCATIONS

Samples from the Carrabassett and Madrid formations were collected in Maine at stops 4, 6, 7, and 8 described in the Hanson et al. (1993) field guide. Rangeley Formation samples were collected in central New Hampshire at stops 1 and 2 of Lyons (1988) and stops 5, 7, and 9 of Eusden (1988). Berwick Formation samples were collected along a traverse starting at Exit 4 on Interstate 93 at Derry, New Hampshire extending eastward on Route 102 to Raymond, New Hampshire. The Eliot Formation was sampled at Stop VI-7 of Bothner (1989) at the junction of Route 155 and US4. Samples of the Kittery Formation were taken from Bothner's Stop VI-8 at Great Bay, New Hampshire, at Ogunquit, Moody Point in Wells, and at Cape Elizabeth, Maine. Approximate sample locations are shown on Figure 2.

ANALYTICAL METHODS

Detrital zircons were obtained from a ca. 5 kg sample of the Carrabassett Formation collected at Stop 4 of Hansen et al. (1993) at the Big Wilson Stream in Elliotsville, Maine. Zircons were extracted at Memorial University of Newfoundland using conventional mineral separation techniques (crushing, Wilfley table, and heavy liquids). Grains from the least magnetic split obtained with a Frantz isodynamic separator were hand picked in alcohol under a binocular microscope. The selected grains were mounted in an epoxy-filled grain mount and polished to obtain a fiat surface. Bulk-rock XRF analyses were conducted on a Siemens SRS 303 instrument in the Department of Geological Sciences at Brigham Young University. Additional trace elements were analyzed by ICP-MS by ALS Chexex in Reno, Nevada.

In situ LA-ICP-MS analyses of areas within the selected crystals of zircon were carried out using a VG PlasmaQuad PQ-2 s+ instrument coupled to a NUWAVE UP213 nm NdYAG laser at Memorial University of Newfoundland. Additional zircons were analyzed with an Element XR coupled to a GEOLAS 193 nm eximer laser system following the methods of Kosler et al. (2002). Raw data were corrected for electron multiplier dead time (20 ns) and processed off-line using an Excel spreadsheet program (LAMDATE) to integrate signals from each sequential set of 10 sweeps; the method follows that of Kosler et al. (2002). The measured [sup.207]Pb/[sup.206]Pb, [sup.208]Pb/[sup.206]Pb, [sup.238]Pb/[sup.238]U, and [sup.207]Pb/[sup.235]U ratios were calculated and blank corrected for each analysis. The natural [sup.238]U/[sup.235]U ratio of 137.88 was used to calculate the [sup.235]U since it was not acquired with other isotopes due to its low natural abundance. Aspiration of the tracer solution allowed for a real-time instrument mass bias correction using known isotopic ratios of the tracer solution measured while the sample was ablated; this technique is largely independent of matrix effects that can variably influence measured isotopic ratios and hence the resulting ages (Kosler et al. 2002; Cox et al. 2003). The amount of common Pb present in the analyzed zircon grains was insignificant relative to the content of radiogenic Pb and therefore, no common Pb correction was applied to the data. Accuracy and reproducibility of U-Pb analysis were monitored by using zircon 91500, a natural in-house zircon standard with a known TIMS U-Pb age of 1065 [+ or -] 3 Ma (Wiedenbeck et al. 1995). Final ages and concordia diagrams were produced using the Isoplot/Ex macro (Ludwig 2000) in conjunction with LAMDATE Excel spreadsheet program (Kosler et al. 2002).

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RESULTS

Bulk-rock Analyses

Bulk-rock major and trace element analyses of the Carrabassett, Rangeley, Smalls Falls, and Madrid formations of the Central Maine Basin and the Kittery, Berwick and Eliot formations of the Merrimack Trough are given in Table 1 and sample locations in Appendix A. Before discussing these results, it is appropriate to discuss how well these metasedimentary rocks represent initial compositions and the potential of element mobility during diagenesis and metamorphism. Cullers et al. (1997) presented a major and trace element and Nd isotopic study of the Rangeley, Perry Mountain, and Smalls Falls formations of western Maine. Their objective was to test the commonly accepted notion that the REE, Th, Sc, Co, and Cr are the most immobile elements during weathering, diagenesis, and metamorphism and as such, can be used to determine the provenance of metasedimentary rocks. They found that most major and trace element abundances relative to [Al.sub.2][O.sub.3] are statistically identical between zones of the same formation as well as between formations, suggesting no mobilization of the elements of interest in these rocks. Systematic compositional variations were attributed to varying proportions of clay minerals, feldspars, and quartz in the original protoliths. Some samples of the Perry Mountain Formation, however, are anomalous in that they have low REE contents and unrealistically old [Nd.sub.TDM] model ages, suggestive of open system behavior. Bock et al. (2004) also found that anomalous REE patterns and old [Nd.sub.TDM] model ages of several formations of the northern Appalachians are indicative of open system behavior. Our samples show neither anomalous REE behavior nor unrealistically old [Nd.sub.TDM] model ages; hence, we assume that the REE, Th, Sc, Co, and Cr concentrations permit determination of provenance characteristics as shown in numerous other studies (Bhatia and Crook 1986; Cox et al. 1995; Cullers 1994, Cullers et al. 1975, 1979, 1997; Wronkiewicz and Condie 1990).

[FIGURE 3 OMITTED]

Log values of Si[O.sub.2]/[Al.sub.2][O.sub.3] versus [Fe.sub.2][O.sub.3]/[K.sub.2]O (Fig. 3) show that the samples (including analyses of Lathrop et al. 1996 and Cullers et al. 1997) plot as shale and wacke with a few samples scattering in the Fe-sandstone field (Herron 1988). The Rangeley Formation is dominated by shale protoliths whereas the other formations are wacke-dominated. Ague (1991, 1997) found evidence of Si[O.sub.2] loss in the Littleton Formation with increasing metamorphic grade so the lower log (Si[O.sub.2]/[Al.sub.2][O.sub.3]) values of the Rangeley Formation compared to the Carrabassett may be influenced by Si[O.sub.2] loss during metamorphism.

Because compatible elements have higher concentrations while incompatible elements have lower abundance in mafic compared to felsic rocks, Cullers et al. (1997) used these ratios to determine the general characteristics of source regions of sediments. Figure 4 illustrates the range of trace element ratios for sediments derived from silicic and mafic sources (Cullers et al. 1997). La/Sc values (Fig. 4a) for the Carrabassett Formation and the Merrimack Trough formations are as low as 0.8 and show good overlap, extending to values as high as 3.6. The lower values fall within the overlap in compositions derived from mafic and silicic sources, suggesting that these formations were derived from intermediate to silicic sources. The Rangeley Formation plots within the silicic provenance range, extending to slightly higher ratios than the Carrabassett and Merrimack sediments. Likewise with Th/Sc values (Fig. 4b): all formations show some samples with intermediate compositions between mafic and silicic sources, but the Rangeley extends to slightly more silicic values. All formations have Th/Co values (Fig. 4c) in the lower range of values for silicic sources. The Cr/Th diagram (Fig. 4d) differs somewhat from the others in that the Merrimack Trough formations are dominated by intermediate values whereas the Carrabassett and Rangeley samples are silicic. On average, the Rangeley Formation has the lowest Cr/Th values, indicating a more consistent silicic source. Even though the lottery and Carrabassett formations have outboard paleocurrent indicators, there is no distinction in trace element ratios of these formations except that the lottery has slightly higher Cr/Th values (Fig. 4d) than most of the Carrabassett samples.

Chrondrite-normalized REE diagrams for Carrabassett, Rangeley, lOttery, Eliot, and Berwick formations are plotted in Fig. 5. All the analyses are quite similar and only show subtle differences in slope and in overall REE abundances. The Carrabassett Formation shows the largest range in REE abundances, with LREE between 36 and 158 times chondrite values and [(La/Lu).sub.N] values between 2.9 and 13 (Table 2; Fig. 5a). The Rangeley Formation has the highest REE abundances and steepest slopes, with LREE ranging between 120 to 247 times chondrite values (Fig. 5b) and an average [(La/Lu).sub.N] value of 10.26. All the Merrimack Trough formations are similar in overall REE abundances and slopes. [(La/Lu)).sub.N] values are 7.09.6 for the Berwick Formation, 6.8-9.9 for the Eliot, and 7.39.7 for the lottery (Fig. 5c, 5d, and 5e). Cullers et al. (1997) found that [(La/Lu)).sub.N] values for sediments derived from silicic rocks range between 3.0 and 27 and mafic rocks between 1.1 and 7.0. The [(La/Lu)).sub.N] values for our sampled formations, regardless of provenance, lie at the lower range of silicic values, again suggesting mixed or intermediate composition source regions.

Average REE concentrations of the Rangeley and lottery formations are shown in Fig. 5f. Because the Carrabassett Formation shows a wide range of values, average compositions for samples with LREE > 100 and < 100 times chondrite values are plotted. Mso plotted are average values for turbidites from fore-arc, Andean-type arc and passive-margin settings (Taylor and McLennon 1985). The > 100 times chondrite Carrabassett Formation average and the Rangeley and lOttery averages are most similar to passive margin turbidites. The < 100 times chondrite Carrabassett average is more similar to fore-arc turbidites. However, none of the compatible/incompatible element ratios in the Carrabassett Formation (Fig. 4) suggest a mafic component as might be expected in a forearc setting. Additionally, all the Carrabassett, Rangeley, and Merrimack samples plot along the trailing edge turbidite field defined by McLennan et al. (1993) in the Zr/Sc versus Th/Sc diagram (Fig. 6).

Nd and Sr Isotopic Compositions

Isotopic compositions of Nd and Sr for the metasedimentary rocks of the Central Maine Basin were published by Lathrop et al. (1996) and are plotted in Fig. 7 with our analyses of the Merrimack Trough formations (Table 2). Lathrop et al. (1996) included one sample of the Carrabassett Formation and two of the Littleton Formation which is thought to be the Carrabassett equivalent in New Hampshire (Moench and Pankiwskyj 1988; Hatch and Moench 1984). All samples plot below bulk-Earth values at [[epsilon].sub.Nd] values between -5 and -10 and [Sr.sub.i] values ranging from 0.7100 to 0.7170. No significant isotopic difference exists between the Carrabassett/Littleton Formation and the Rangeley Formation which has Laurentian provenance. All Merrimack Trough samples, including those from the Kittery Formation, plot in the Central Maine Basin field, identical to the Carrabassett and Rangeley formation samples. Thus, regardless of whether the Carrabassett and Kittery formations have paleocurrent indicators of an offshore source, their isotopic signatures are no different from the Rangeley Formation metasedimentary rocks that were derived from Laurentia.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

Carrabassett/Littleton Formation Nd model ages average 1.7 Ma (Lathrop et al. 1996) as do the averages of the formations from the Merrimack Trough (Table 2). Rangeley Formation and other Laurentia-derived formations have Nd model ages that average 1.61 Ma (Lathrop et al. 1996). These ages are similar to the non-altered samples of Cullers et al. (1997) and Bock et al. (2004), suggesting that the samples of Lathrop et al. (1996) represent original provenance signatures. McLennan et al. (1993) combined Nd isotopic data with Th/ Sc ratios to distinguish active arc and trailing edge turbidites (Fig. 8). Active arc turbidites define the non-quartzose field, comprising sediments that are dominated by mafic sources. The majority of these sediments plot at positive end and low Th/Sc values. In contrast, turbidites derived from trailing edge settings are quartzose with negative end values. The Merrimack Trough formations plot in the quartzose field with no distinction between the Kittery Formation and the Eliot/Berwick analyses. Although we lack Nd isotopic data on our Carrabassett Formation samples, they have the same Th/Sc values as the Merrimack metasedimentary rocks and Lathrop et al. (1996) reported the same range in end values for the Littleton as the Merrimack; thus the Carrabassett Formation would plot among the Merrimack samples which are derived from a nonjuvenile, quartzose source.

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Detrital Zircon Geochronology

A plot of [sup.207]Pb/[sup.235]U versus [sup.206[Pb/[sup.238]U for detrital zircons from the Carrabassett Formation is shown in Fig. 9. Plotted data are within [+ or -]10% of concordancy and the data point error ellipses are 1[sigma]. The complete data set is given in Table 3. A relative probability and histogram diagram is plotted in Fig. 10a. A potential Acadian zircon fraction is present with an age of 412 [+ or -] 23 Ma. Zircon grains with Taconic-like ages are present also, with ages of 445 [ + or -] 29 and 482 [ + or -] 12 Ma. A dominant peak is centered at ~600 Ma. The most prominent peak on the diagram ranges from 900 to 1440 Ma, centered at 1200 Ma. Individual grains have older ages of ~1500-1600,1800, 2080, 2200, and 2600 Ma. The paucity of ~600 Ma and 1490-1610 zircons in Laurentia presents an obvious difference between Laurentia and the Carrabassett Formation (Sampson et al. 2005). Likewise, two grains centered around 2280 Ma in the Carrabassett Formation contrast with the absence of grains of that age in Avalonia (Samson et al. 2005).

Comparisons of Carrabassett Formation detrital zircons with available zircon ages from Ganderia are presented in Fig. 10b. Ganderia ages are for inherited zircons derived from plutonic rocks and boulders thought to represent the unexposed basement (Roddick and Bevier 1995; van Staal et al. 1996), from orthogneisses of the Lyme Dome, Connecticut (Walsh et al. 2007), and from metasedimentary rocks east of the Dog Bay Line, Newfoundland (Pollock et al. 2007). Good matches are evident between the Carrabassett and Ganderia supracrustal rocks with strong similarities at ~600 Ma and the common peak centered at ~1200 Ma.

DISCUSSION

Bulk-Rock Geochemistry

The above results show that there are no significant bulkrock geochemical differences between Laurentia-derived sediments as typified by our Rangeley Formation samples and the easterly derived Carrabassett and Kittery formations. The Carrabassett Formation, with an outboard source, has similar trace element ratios as the Rangeley Formation. Likewise, the Kittery Formation, which also has outboard paleocurrent indicators, is no different than the Berwick and Eliot formations of the Merrimack Trough nor is it significantly different from the Laurentia-derived Rangeley Formation. Thus all the formations appear to have been derived from source regions that were neither dominated by mafic rocks such as found in primitive arcs nor exclusively by silicic rocks. Rather, it is plausible that the sediments were produced from large areas that homogenized to an average intermediate composition. The intermediate composition is also supported by REE abundances. The Rangeley, Berwick, Eliot, and Kittery formations and the > 100 times chondritic portion of the Carrabassett Formation all have REE abundances most similar to passive margin turbidites (Fig. 5), an inference supported by the Zr/Sc verus Th/ Sc diagram (Fig. 6).

[FIGURE 10 OMITTED]

Isotopic data (Fig. 7) show no differences between Central Maine Basin metasedimentary rocks, including the Rangeley Formation, and either the Carrabassett Formation or the Merrimack Trough formations. All the metasedimentary samples fall in a relatively narrow range of end values between -6 and -10. This range differs considerably from Avalonian granites commonly used to define the basement of Avalonia (Nance and Murphy 1994; Nance et al. 2002; Murphy and Nance 2002) in that most of the granites have positive [[epsilon].sub.Nd] values. Many workers have therefore concluded that Avalonia consists primarily of juvenile crust which is isotopically distinct from older materials derived from Laurentia. In contrast, Ganderian plutons tend to have negative [[epsilon].sub.Nd] values of the same range as the Carrabassett and Kittery metasedimentary rocks (Roddick and Bevier 1995; van Staal et al. 1996). The Nd model ages of the Carrabassett Formation (Lathrop et al. 1996) and the Kittery Formation average 1.70 Ma and 1.74 Ma, respectively. These ages are far older than the age of Avalonia, which is dominated by juvenile arc rocks of ~600 Ma and Neoproterozoic model ages (Nance and Murphy 1994; Nance et al. 2002; Murphy and Nance 2002), but are similar to Ganderian model ages (Whalen et al. 1996, 1997; Schofield and D'Lemos 2000). Thus it appears that both the Carrabassett and Kittery formations potentially match Ganderian but not Avalonian basement.

The picture is complicated when one considers the Neoproterozoic through Cambrian supracrustal rocks associated with Avalonia. A recent study by Satkoski et al. (2007) showed that some of the sedimentary cover rocks of the Avalonian Caledonia terrane of New Brunswick have positive [[epsilon].sub.Nd] values and are interpreted as being derived from Avalonian sources. However, other metasedimentary units have negative end values and were interpreted as originating from a large, isotopically mature source (Samson et al. 2000; Murphy 2002; Satkoski et al. 2007). These Avalonian supracrustal rocks are interpreted as being derived from older, Gondwanan sources and deposited on Avalonian basement (Satkoski et al. 2007). Therefore, based on bulk-rock [[epsilon].sub.Nd] values alone, we cannot exclude the possibility that the Carrabassett Formation could be dominated by recycled Avalonian supracrustal rocks rather than juvenile Avalonian basement. However, the abundance of Avalonian supracrustal rocks with mature crustal signatures appears to be relatively small and the odds of the Carrabassett Formation exclusively representing recycling of such supracrustal rocks seems low. Additionally, the available detrital zircon ages of these supracrustal rocks are considerably different than those of the Carrabassett Formation (compare Fig. 10a with 10c).

It appears that no bulk-rock characteristics, either trace element or isotopic, can clearly distinguish the Laurentia-derived Rangeley from peri-Gondwanan Carrabassett or Kittery formations. As it has been shown that Quaternary sediments sampiing large continental masses have remarkably uniform [[epsilon].sub.Nd] values of ~-11 and [T.sub.DM] of 1.9 Ga (Goldstein et al. 1984, 1997; Goldstein and Jacobsen 1988), we interpret this lack of unique bulk-rock compositions of sediments derived from Laurentia (Rangeley Formation) and Gondwana (Carrabassett/Kittery formations) as signifying that the formations represent sediments derived from large regions of mature continental crust which homogenized their bulk-rock characteristics. These characteristics differ from the juvenile Avalonian crust, but not necessarily from Avalonian supracrustal rocks.

Geochronology

Although there are similarities between the ages of detrital zircon grains in the Carrabassett Formation and those of Laurentia, a noticeable difference is the paucity of ~600 and 1490 to 1610 Ma zircons in the Laurentian populations, which points to a non-Laurentian component for the Carrabassett Formation sedimentary rocks. The Carrabassett Formation ages cluster at ~1200 Ma, perhaps representing a Grenvillian component derived from Laurentia, but as demonstrated by van Staal et al. (1996), such ages are also common in peri-Gondwanan Ganderia. Thus, based on detrital zircon geochronology, a Ganderian source is plausible. Figure 10b compares relative probability plots for Carrabassett Formation zircons with those of Ganderia (Roddick and Bevier 1995; van Staal et al. 1996; Pollock et al. 2007; Walsh et al. 2007). There are strong similarities at 500-700 Ma, 1000-1400 Ma, and ~1750 Ma. These similarities, along with the similar Nd isotopic values and model ages, and a passive margin depositional setting for Ganderia (Williams 1979; van der Pluijm and van Staal 1988) that is also characteristic of the Carrabassett Formation (Fig. 5f and Fig. 6), indicate that Ganderia may have been the source for the easterly derived sediments that became the Carrabassett Formation.

In contrast, the detrital zircon ages from Avalonian metasedimentary rocks (Keppie et al. 1998; Barr et al. 2003; Murphy et al. 2004) shown in Fig. 10c have some similarities to the Carrabassett Formation ages, but are of vastly different proportions. The Kittery Formation of the Merrimack Trough has a relative probability plot that is also different from the Carrabassett Formation, even though Wintsch et al. (2007) considered the Kittery Formation to be derived from Gondwana. The Kittery Formation has a prominent peak at ~1000 Ma whereas the most prominent peak in the Carrabassett Formation is at ~1200 Ma. Additionally, the Carrabassett Formation has a well-defined peak at ~600 Ma; the Kittery Formation yielded only one zircon of that age. Therefore, even though the Kittery Formation has an outboard source that may be Gondwanan (Wintsch et al. 2007), the detritial zircon ages indicate that this source was different from that of the Carrabassett Formation. This difference may not be a surprise given the up to 70 Ma age difference between the two formations.

Provenance and tectonic setting of the Carrabassett Formation

The criteria for assigning Ganderian provenance to the Carrabassett Formation are summarized in Fig. 11. Although some bulk-rock characteristics match other terranes, one or more mismatches suggest that these terranes were not Carrabassett Formation sources. Paleocurrent indicators suggest an outboard source, suggestive of either Ganderia or Avalonia. Bulk-rock major and trace element concentrations, the bulk-rock Nd isotopic compositions, and the Nd model ages do not discriminate between Ganderian, Avalonian supracrustal, or Laurentian sources because all three of those sources represent mature, continental crust. These parameters do however, eliminate the juvenile arc portion of Avalonia, and since this is the dominant component of Avalonia, these mismatches minimize the possibility of an Avalonian provenance. The detrital zircon ages eliminate Laurentia and the younger juvenile Avalonia as sources. While the Avalonian supracrustal rocks are permissible source rocks for the Carrabassett sediments based on bulk-rock characteristics, the detrital zircon ages of the supracrustal rocks (Barr et al. 2003; Samson et al. 2005) differ from those of the Carrabassett Formation. In contrast, the detrital zircon ages of the Carrabassett Formation are a good match for Ganderian ages. Thus the only potential source that matches all measured characteristics of the Carrabassett Formation is Ganderia.

A Ganderian provenance is in apparent contrast to tectonic scenarios which indicate that Ganderia was already accreted to Laurentia (~430 Ma, van Staal et al. 2004, 2006), apparently serving as basement upon which the sediments of the Central Maine Basin, including the Carrabassett Formation, were deposited. However, the eastern margin of Ganderia may have been exposed in the early Devonian if crustal-scale wedging of Ganderia by Avalonia as proposed for eastern Newfoundland (van der Velden et al. 2004) also occurred in northern New England. The likelihood of this scenario is increased by the identification of similar wedging along the Ganderia-Avalonia boundary in southern New England (Aleinikoff et al. 2007; Walsh et al. 2007).

We envision the wedging of Ganderian crust by the Avalonian indenter to have initiated with the Salinic orogeny in the early to middle Silurian. The closure around Ganderia would have lead to interference among the lithospheric mantles of Laurentia, Ganderia, and Avalonia, apparently resulting in delamination of the lithospheric mantle of Ganderia. During early stages of delamination the mantle likely created a keel, causing subsidence of the basin. To the east, where Ganderian and Avalonian crusts interacted, wedging caused slices of Ganderia to override Avalonia (Wintsch et al. 1992). The consequent crustal thickening created relief (Fig. 12). Erosion and transportation yielded sediments with westward paleocurrent directions (Bradley and Hanson 1989, 2002) and geochemical signatures and a detrital zircon suite consistent with a Ganderian passive margin source. Potential specific Ganderian source regions include the Miramichi, a known Ganderian highland at that time (Pickerill and Fyffe 1999), and the Liberty-Orrington and St. Croix sequences (van Staal et al. 1996; Tucker et al. 2001; Reusch et al. 2006).

Provenance and tectonic setting of the Kittery Formation

Wintsch et al. (2007) noted that the Kittery Formation contains primarily Mesoproterozoic detrital zircons; only two of their analyses ware younger. Paleocurrent directions from the east and the absence of a significant Ordovician age population in the formation led Wintsch and coworkers to suggest that the formation was derived from peri-Gondwanan sources and deposited in the Fredericton Sea, farther east of the Miramichi arch (Tucker et al. 2001). A Fredericton Sea origin for the Kittery sediments could explain the differences in the relative probability plots of the Carrabassett and Kittery formations shown in Fig. 10.

CONCLUSIONS

The Carrabassett Formation of western Maine is the youngest, most widespread pre-Acadian formation of the Central Maine Basin. The sediments were deposited in a northwestmigrating trench slope during the initial stages of the Acadian orogeny and represent a pulse of sediment derived from Ganderia to the east. The detrital zircons in the Carrabassett Formation are most compatible with chronological fingerprints of Ganderia, specifically the dominant population of ages of ~600 Ma and 900-1440 Ma. Both the Carrabassett Formation and Ganderia have zircons with ages of ~600 Ma and between 2000-2400 Ma, ages that are rare to absent in Laurentia and Avalonia, respectively. REE abundances and Zr/Sc versus Th/Sc ratios suggest trailing edge turbidites for the Carrabassett and Kittery formations, reflecting the passive margin setting of Ganderia.

[FIGURE 12 OMITTED]

Carrabassett Formation bulk-rock [[epsilon.sub.Nd] (413 MR)Values are negative (-8 to -10), unlike the positive values for juvenile Avalonian crust. Similar negative values for Laurentia-derived sediments in the Central Maine Basin (Rangeley Formation) and peri-Gondwana-derived Merrimack Trough sediments indicate the inability of bulk-rock [[epsilon].sub.Nd] values to discriminate Laurentian and Gondwanan sources when sediments were derived form large regions of mature crust. Unless the sedimentary source is restricted to and dominated by juvenile arc detritus such as Avalonian crust, mixing of sediment yields an intermediate crustal composition, as does bulk-rock incompatible/compatible element ratios.

Even though Ganderia was basement to the sediments of the Central Maine Basin, tectonic wedging of Avalonia into Ganderia is inferred to have uplifted Ganderia outboard of the Central Maine Basin, permitting shedding of Ganderia-derived sediments to the west as the first outboard pulse of sediment. We infer that the collision of Avalonia with the Taconic- and Salinic-modified Laurentian margin did indeed cause the Acadian orogeny in New England, but because the leading edge of Avalonia wedged mid-crustal Ganderia, the portion of Avalonia that experienced Acadian metamorphism lies beneath Ganderian rocks in eastern New England.
Appendix A. Sample locations for bulk-rock analyses based on best
estimates from Google Earth.

Carrabassett Formation

Sample    Latitude                 Longitude

H-2       45[degrees]22'08.69"N    69[degrees]26'12.00"W
H-3       45[degrees]22'08.69"N    69[degrees]26'12.00"W
H-5       45[degrees]18'14.05"N    69[degrees]26'09.13"W
H-6       45[degrees]18'14.05"N    69[degrees]26'09.13"W
H-7       45[degrees]18'14.05"N    69[degrees]26'09.13"W
H-8       45[degrees]18'14.05"N    69[degrees]26'09.13"W
H-9       45[degrees]16'16.01"N    69[degrees]28'56.98"W
H-10      45[degrees]16'16.01"N    69[degrees]28'56.98"W
H-11      45[degrees]22'08.69"N    69[degrees]26'12.00"W

Rangeley Formation

R-2-1     43[degrees]27'42.29"N    71[degrees]40'19.05"W
R-2-2     43[degrees]27'42.29"N    71[degrees]40'19.05"W
R-3-1     43[degrees]27'42.29"N    71[degrees]40'19.05"W
R-3-2     43[degrees]27'42.29"N    71[degrees]40'19.05"W
R-5-1     43[degrees]23'00.61"N    71[degrees]26'29.31"W
R-5-2     43[degrees]23'00.61"N    71[degrees]26'29.31"W
R-6-1     43[degrees]23'00.61"N    71[degrees]26'29.31"W
R-6-2     43[degrees]23'00.61"N    71[degrees]26'29.31"W
R-6-3     43[degrees]23'00.61"N    71[degrees]26'29.31"W

Madrid Formation

H-12      45[degrees]04'07.44"N    69[degrees]54'21.80"W
H-13      45[degrees]04'06.96"N    69[degrees]54'20.99"W
H-14      45[degrees]04'06.92"N    69[degrees]54'20.43"W
H-15      45[degrees]04'05.74"N    69[degrees]54'18.10"W
H-16      45[degrees]04'05.11"N    69[degrees]54'15.63"W
H-19      44[degrees]57'27.64"N    69[degrees]52'13.27"W
H-20      44[degrees]57'27.64"N    69[degrees]52'13.27"W

E-1       42[degrees]52'12.25"N    70[degrees]58'41.32"W
E-2       42[degrees]52'12.25"N    70[degrees]58'41.32"W
E-3       42[degrees]52'12.25"N    70[degrees]58'41.32"W
E-4       42[degrees]52'12.25"N    70[degrees]58'41.32"W

Kittery Formation

K-1       43[degrees]05'28.42"N    70[degrees]51'55.75"W
K-4       43[degrees]14'40.28"N    70[degrees]35'27.76"W
K-6       43[degrees]14'40.28"N    70[degrees]35'27.76"W
K-9       43[degrees]17'14.97"N    70[degrees]34'12.78"W
K-11      43[degrees]33'30.57"N    70[degrees]12'18.45"W
K-12      43[degrees]33'30.57"N    70[degrees]12'18.45"W

Berwick Formation

B-1       42[degrees]52'12.25"N    71[degrees]20'37.44"W
B-2       42[degrees]52'10.60"N    71[degrees]20'37.07"W
B-3       42[degrees]52'10.60"N    71[degrees]20'37.07"W
B-4       42[degrees]52'10.60"N    71[degrees]20'37.07"W
B-5       42[degrees]53'59.80"N    71[degrees]18'18.43"W
B-6       42[degrees]53'59.80"N    71[degrees]18'18.43"W
B-8       42[degrees]58'54.34"N    71[degrees]13'17.24"W
B-9       43[degrees]00'01.50"N    71[degrees]10'33.21"W


ACKNOWLEDGMENTS

We thank Dwight Bradley for a helpful review of an earlier version of the manuscript, Cees van Staal for many helpful discussions, and two anonymous reviewers and Sandra Barr whose suggestions contributed to improving the manuscript. Initial research funds were provided by the College of Physical and Mathematical Sciences of Brigham Young University, followed by National Science Foundation (EAR-0510857) funds to Robert P. Wintsch and Michael J. Dorais.

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Editorial responsibility: Sandra M. Barr

MICHAEL J. DORAIS (1) *, ROBERT P. WINTSCH (2), WENDY R. NELSON (3), AND MICHAEL TUBRETT (4)

(1.) Department of Geological Sciences, Brigham Young University, Provo, Utah 84602, USA

(2.) Department of Geological Sciences, Indiana University, Bloomington, Indiana 47405, USA

(3.) Department of Geosciences, Penn State University, University Park, Pennsylvania 16802, USA

(4.) CREAIT Network, Micro Analysis Facility, Inco Innovation Centre (MAF-IIC), Memorial University, St. John's, Newfoundland A1B 3X5, Canada

* Corresponding author: <dorais@byu.edu>

Date received: 07 July 2008 [paragraph] Date accepted: 11 February 2009

doi: 10.4138/atlgeol.2009.002
Table 1. Bulk-rock Analyses of samples from the Central Maine and
Merrimack Trough.

Sample                   Si[O.sub.2]    Ti[O.sub.2]

Carrabassett Formation
  H-2                       83.90           0.54
  H-3                       72.01           0.94
  H-5                       83.20           0.59
  H-6                       76.89           0.66
  H-7                       75.90           0.73
  H-8                       71.35           0.87
  H-9                       67.06           0.91
  H-10                      70.58           1.01
  H-11                      81.02           0.55
Rangeley Formation
  R-2-1                     71.60           0.81
  R-2-2                     73.40           0.81
  R-3-1                     71.30           0.86
  R-3-2                     72.20           0.81
  R-5-1                     71.30           0.87
  R-5-2                     59.00           0.96
  R-6-1                     73.40           0.79
  R-6-2                     74.20           0.77
  R-6-3                     71.20           0.68

Madrid Formation
  H-12                      71.03           0.66
  H-13                      71.26           0.79
  H-14                      55.11           0.66
  H-15                      71.34           0.69
  H-16                      55.92           0.93
  H-19                      66.44           0.54
  H-20                      68.02           0.61

Eliot Formation
  E-1                       66.03           0.68
  E-2                       66.03           0.76
  E-3                       55.68           0.75
  E-4                       62.00           0.63

Kittery Formation
  K-1                       70.06           0.64
  K-4                       45.44           3.00
  K-6                       56.31           0.86
  K-9                       64.75           0.66
  K-11                      68.56           0.66
  K-12                      69.14           0.67

Berwick Formation
  B-1                       69.81           0.68
  B-2                       70.00           0.71
  B-3                       71.19           0.87
  B-4                       60.50           0.88
  B-5                       70.47           0.59
  B-6                       68.69           0.67
  B-8                       67.36           0.80
  B-9                       68.12           0.67

Sample                   [Al.sub.2][O.sub.3]

Carrabassett Formation
  H-2                            5.75
  H-3                           13.40
  H-5                            7.51
  H-6                            9.72
  H-7                           10.46
  H-8                           12.64
  H-9                           15.30
  H-10                          13.34
  H-11                           6.58
Rangeley Formation
  R-2-1                         11.95
  R-2-2                         11.75
  R-3-1                         13.05
  R-3-2                         12.60
  R-5-1                         13.13
  R-5-2                         18.74
  R-6-1                         10.88
  R-6-2                         10.35
  R-6-3                         11.64

Madrid Formation
  H-12                          11.50
  H-13                          12.44
  H-14                          12.60
  H-15                          11.85
  H-16                          18.85
  H-19                           9.73
  H-20                          12.52

Eliot Formation
  E-1                            9.28
  E-2                            9.41
  E-3                           14.54
  E-4                           11.53

Kittery Formation
  K-1                           11.61
  K-4                           15.82
  K-6                           16.96
  K-9                           11.95
  K-11                           9.89
  K-12                          11.70

Berwick Formation
  B-1                           10.74
  B-2                           11.38
  B-3                           11.81
  B-4                           14.62
  B-5                           11.63
  B-6                           12.24
  B-8                           14.30
  B-9                           11.75

Sample                   [Fe.sub.2][O.sub.3.sup.t]     MnO     MgO

Carrabassett Formation
  H-2                               6.40               0.11    0.77
  H-3                               6.10               0.06    1.19
  H-5                               4.45               0.03    0.79
  H-6                               5.71               0.07    1.38
  H-7                               5.69               0.07    1.36
  H-8                               5.83               0.06    1.84
  H-9                               7.21               0.10    2.10
  H-10                              5.91               0.08    1.68
  H-11                              7.22               0.15    1.01
Rangeley Formation
  R-2-1                             7.01               0.20    1.94
  R-2-2                             6.83               0.11    1.90
  R-3-1                             6.80               0.10    2.13
  R-3-2                             7.08               0.13    2.13
  R-5-1                             6.31               0.06    1.37
  R-5-2                             8.97               0.08    2.13
  R-6-1                             6.14               0.18    1.68
  R-6-2                             6.66               0.15    1.82
  R-6-3                             5.28               0.26    1.53

Madrid Formation
  H-12                              4.54               0.06    2.52
  H-13                              4.85               0.05    2.62
  H-14                              4.66               0.17    7.06
  H-15                              4.50               0.07    2.38
  H-16                              8.64               0.10    4.99
  H-19                              3.15               0.13    1.71
  H-20                              5.01               0.06    2.84

Eliot Formation
  E-1                               3.76               0.07    2.58
  E-2                               3.82               0.07    2.59
  E-3                               6.75               0.07    4.47
  E-4                               4.77               0.07    3.02

Kittery Formation
  K-1                               4.49               0.06    3.08
  K-4                              13.07               0.20    5.67
  K-6                               7.37               0.11    4.83
  K-9                               5.06               0.06    3.29
  K-11                              3.98               0.08    2.51
  K-12                              4.65               0.06    3.11

Berwick Formation
  B-1                               4.12               0.12    2.54
  B-2                               4.40               0.07    2.95
  B-3                               4.58               0.07    3.13
  B-4                               6.61               0.10    4.30
  B-5                               4.22               0.10    2.91
  B-6                               4.53               0.12    3.39
  B-8                               5.85               0.09    2.65
  B-9                               4.49               0.08    3.08

Sample                    CaO    [Na.sub.2]O    [K.sub.2]O

Carrabassett Formation
  H-2                     0.21           1.22          0.10
  H-3                     0.27           1.22          2.62
  H-5                     0.10           1.18          0.90
  H-6                     0.11           1.07          1.64
  H-7                     0.11           1.06          1.89
  H-8                     0.16           1.64          2.16
  H-9                     0.69           1.78          2.99
  H-10                    0.35           1.51          2.73
  H-11                    0.22           0.77          0.49
Rangeley Formation
  R-2-1                   1.31           2.07          1.68
  R-2-2                   0.34           0.67        2..52
  R-3-1                   0.56           1.12          2.66
  R-3-2                   0.54           0.95          2.33
  R-5-1                   0.94           1.77          2.61
  R-5-2                   0.29           0.81          4.41
  R-6-1                   1.63           2.74          1.83
  R-6-2                   1.32           2.15          1.78
  R-6-3                   3.68           1.91          1.50

Madrid Formation
  H-12                    3.12           2.01          2.23
  H-13                    1.97           2.95          2.25
  H-14                    9.15           1.36          2.93
  H-15                    3.16           2.56          2.05
  H-16                    0.63           1.37          6.13
  H-19                    8.62           1.65          1.29
  H-20                    3.67           2.49          2.23

Eliot Formation
  E-1                     5.60           1.88          1.98
  E-2                     5.52           1.66          2.24
  E-3                     4.33           1.48          3.16
  E-4                     5.42           1.66          2.84

Kittery Formation
  K-1                     3.05           2.06          2.54
  K-4                     8.60           3.61          1.42
  K-6                     6.07           1.99          3.16
  K-9                     3.15           1.27          2.81
  K-11                    5.16           2.20          1.75
  K-12                    2.83           2.15          1.82

Berwick Formation
  B-1                     7.15           1.50          2.06
  B-2                     4.60           1.97          2.22
  B-3                     3.28           2.01          2.12
  B-4                     8.11           1.99          2.09
  B-5                     7.73           1.16          0.50
  B-6                     6.39           0.64          1.56
  B-8                     2.93           2.18          2.62
  B-9                     6.14           1.83          2.49

Sample                   [P.sub.2][O.sub.5]      LOI     Total     CIA

Carrabassett Formation
  H-2                           0.11             1.11    100.22    69.7
  H-3                           0.13             2.41    100.35    71.5
  H-5                           0.09             1.27    100.11    70.8
  H-6                           0.10             1.76     99.11    72.2
  H-7                           0.12             1.87     99.26    72.4
  H-8                           0.14             2.35     99.04    70.4
  H-9                           0.13             2.30    100.56    67.3
  H-10                          0.15             2.01     99.35    68.7
  H-11                          0.15             1.51     99.67    75.0
Rangeley Formation
  R-2-1                         0.33             1.69    100.59    61.1
  R-2-2                         0.08             1.88    100.29     725
  R-3-1                         0.07             1.69    100.34     695
  R-3-2                         0.05             1.64    100.46    71.3
  R-5-1                         0.08             2.17    100.61    63.8
  R-5-2                         0.11             3.70     99.20    73.9
  R-6-1                         0.07             1.00    100.34    53.5
  R-6-2                         0.03             1.06    100.29    56.8
  R-6-3                         0.64             2.07    100.39    50.4


Madrid Formation
  H-12                          0.13             2.05     99.85    50.2
  H-13                          0.14             0.57     99.89    53.4
  H-14                          0.10             5.84     99.64    36.4
  H-15                          0.13             1.89    100.61    49.3
  H-16                          0.18             2.35    100.08    65.3
  H-19                          0.14             6.77    100.17    33.0
  H-20                          0.12             2.42     99.99    48.7

Eliot Formation
  E-1                           0.15             8.61    100.62    37.6
  E-2                           0.18             8.37    100.65    38.2
  E-3                           0.15             8.10     99.48    51.4
  E-4                           0.12             8.41    100.47    42.4

Kittery Formation
  K-1                           0.12             3.04    100.75    49.8
  K-4                           0.61             3.14    100.58    40.6
  K-6                           0.15             1.61     99.42    48.9
  K-9                           0.14             6.29     99.43    52.4
  K-11                          0.13             5.74    100.66    39.9
  K-12                          0.15             4.29    100.57    52.3

Berwick Formation
  B-1                           0.12             1.02     99.86    37.8
  B-2                           0.15             2.05    100.50    44.8
  B-3                           0.17             1.18    100.41    50.5
  B-4                           0.17             1.02    100.39    41.9
  B-5                           0.14             0.98    100.43    41.3
  B-6                           0.16             1.20     99.59    46.0
  B-8                           0.14             1.00     99.92    54.9
  B-9                           0.14             0.58     99.37    41.1

Sample                    Rb     Cs     Sr     Ba      La         Ce

Carrabassett Formation
  H-2                       7     76    118     19    36.0       76.0
  H-3                     117     28     89    429    14.5       27.5
  H-5                      42     28     52    164    12.5       27.5
  H-6                      77     19     43    287     8.5       19.0
  H-7                      85     22     46    324    11.0       21.5
  H-8                     105     29     84    365    12.5       28.5
  H-9                     163     39    173    430    19.0       38.5
  H-10                    127     75    110    424    36.5       74.5
  H-11                     27     78     75     76    37.5       78.0
Rangeley Formation
  R-2-1                    86    2.5    111    237    44.0       88.0
  R-2-2                   107    2.3     99    689    35.5       73.0
  R-3-1                   113    3.1    135    730    39.0       80.5
  R-3-2                   111      3     99    657    38.0       79.5
  R-5-1                   160    7.4    211    408    28.5       63.5
  R-5-2                   210    9.8     91    656    58.5      118.5
  R-6-1                   103    3.1    179    351    39.0       79.0
  R-6-2                    97      3    173    376    37.5       76.0
  R-6-3                    75    2.3    189    308    36.0       69.0

Madrid Formation
  H-12                     95     69    202    389    33.0       68.5
  H-13                     88     43    190    403    21.5       42.5
  H-14                    121     76    380    497    37.0       75.5
  H-15                     82     67    223    369    32.5       67.0
  H-16                    194     44     85    898    22.5       43.5
  H-19                     61     51    382    286    25.5       51.0
  H-20                     97     54    225    393    28.5       54.0

Eliot Formation
  E-1                      74      2    225    288    33.5       72.0
  E-2                      83    2.2    224    313    39.5       85.0
  E-3                     130    3.9    203    473    32.0       66.0
  E-4                     107    3.2    224    387    28.5       61.0

Kittery Formation
  K-1                     112    4.1    189    405    27.0       58.0
  K-4                      43    1.1    543    282    34.0       69.0
  K-6                     168    8.6    314    329    37.5       78.5
  K-9                     117    5.2    133    403    31.5       67.5
  K-11                     65    2.2    180    245    28.0       60.0
  K-12                     61    1.9    138    399    34.0       71.0

Berwick Formation
  B-1                      74    8.9    319    420    33.5       70.5
  B-2                      95    4.5    205    355    34.5       73.0
  B-3                      94    4.4    215    370    45.5       88.0
  B-4                      96    7.7    254    399    29.0       68.5
  B-5                      56    8.5    244    114    27.5       57.5
  B-6                      89     13    202    263    37.0       74.0
  B-8                     132     16    177    484    25.5       80.0
  B-9                      82    4.4    232    403    33.5       69.5

Sample                     Pr        Nd       Sm      Eu      Gd

Carrabassett Formation
  H-2                      9.1      32.0      5.7     1.2     5.3
  H-3                      3.7      12.5      2.5     0.5     2.5
  H-5                      3.1      11.0      2.1     0.5     2.1
  H-6                      2.3       7.0      1.5     0.4     1.7
  H-7                      2.6       9.5      2.1     0.6     2.6
  H-8                      3.2      11.0      2.5     0.5     2.7
  H-9                      4.4      16.0      3.0     0.7     2.9
  H-10                     8.6      31.0      5.9     1.4     6.6
  H-11                     8.8      33.5      6.7     2.0     7.7
Rangeley Formation
  R-2-1                    9.8      40.0      8.3     1.5     8.5
  R-2-2                    8.8      33.0      6.0     1.2     5.4
  R-3-1                    9.0      37.0      6.6     1.5     6.3
  R-3-2                    9.0      36.0      5.0     1.4     5.0
  R-5-1                    6.5      25.0      5.2     1.3     4.2
  R-5-2                   13.5      51.0      9.3     1.5     8.5
  R-6-1                    9.1      13.0      6.0     1.5     5.5
  R-6-2                    8.9      12.0      5.5     1.4     5.3
  R-6-3                    8.5      12.0      6.5     1.0     6.3

Madrid Formation
  H-12                     7.8      28.0      5.6     1.3     6.1
  H-13                     5.1      18.5      3.4     1.1     3.9
  H-14                     9.1      31.0      6.1     1.3     6.1
  H-15                     8.1      29.0      5.6     1.1     5.6
  H-16                     5.1      18.5      3.4     0.7     3.7
  H-19                     6.0      21.0      4.5     1.1     4.8
  H-20                     6.7      23.5      4.7     1.0     4.9

Eliot Formation
  E-1                      9.2      35.0      7.1     1.6     6.1
  E-2                     10.8      41.0      7.9     1.6     6.6
  E-3                      8.3      30.5      6.1     1.3     4.9
  E-4                      7.8      29.0      5.8     1.2     4.7

Kittery Formation
  K-1                      7.4      27.5      5.5     1.2     4.7
  K-4                      8.7      35.5      7.3     2.3     6.5
  K-6                     10.0      36.5      7.0     1.3     5.9
  K-9                      8.9      33.0      6.4     1.4     5.7
  K-11                     7.7      29.0      5.7      11     5.3
  K-12                     9.1      33.0      6.7     1.3     5.6

Berwick Formation
  B-1                      8.9      33.0      6.6     1.4     5.6
  B-2                      9.3      35.0      7.0     1.4     5.9
  B-3                     11.9      43.5      8.6     1.8     7.2
  B-4                      8.4      31.0      6.3     1.5     5.8
  B-5                      7.4      27.0      5.6     1.3     4.9
  B-6                      9.5      35.0      6.7     1.5     6.1
  B-8                      6.2      22.5      4.6     1.3     3.7
  B-9                      8.8      32.5      6.6     1.4     5.6

Sample                    Tb      Dy      Ho      Er      Tm      Yb

Carrabassett Formation
  H-2                     0.7     3.9     0.8     2.3     0.4     2.3
  H-3                     0.4     2.4     0.5     1.6     0.3     1.7
  H-5                     0.3     1.7     0.4     1.1     0.1     1.1
  H-6                     0.3     1.7     0.4     1.1     0.1     1.2
  H-7                     0.5     3.4     0.8     2.3     0.4     2.4
  H-8                     0.5     2.6     0.6     1.7     0.3     1.6
  H-9                     0.4     2.5     0.5     1.5     0.2     1.5
  H-10                    1.0     6.3     1.3     3.7     0.6     3.8
  H-11                    0.9     4.9     0.9     2.6     0.4     2.6
Rangeley Formation
  R-2-1                   1.0     6.6     1.3     3.9     0.5     3.4
  R-2-2                   0.6     3.8     0.8     2.9     0.4     2.5
  R-3-1                   0.7     4.7     0.9     2.7     0.4     2.8
  R-3-2                   0.6     4.3     0.8     2.4     0.4     3.1
  R-5-1                   0.6     3.9     0.9     2.5     0.4     2.5
  R-5-2                   0.8     6.3     1.3     3.7     0.6     3.9
  R-6-1                   0.7     4.2     0.9     2.7     0.4     2.6
  R-6-2                   0.7     4.3     0.9     2.6     0.4     2.8
  R-6-3                   0.7     4.8     0.9     2.7     0.4     2.7

Madrid Formation
  H-12                    0.9     4.7     1.0     3.0     0.5     2.8
  H-13                    0.6     3.4     0.8     2.5     0.4     2.8
  H-14                    0.9     4.6     1.0     3.1     0.4     2.8
  H-15                    0.8     4.5     0.9     2.7     0.4     2.5
  H-16                    0.5     3.0     0.6     1.8     0.3     1.8
  H-19                    0.7     3.9     0.9     2.4     0.3     2.3
  H-20                    0.7     3.8     0.8     2.3     0.3     2.1

Eliot Formation
  E-1                     1.1     5.5     1.3     3.5     0.6     3.2
  E-2                     1.2     6.0     1.4     3.9     0.6     3.8
  E-3                     0.9     4.5     1.1     2.9     0.4     2.7
  E-4                     0.9     4.0     0.9     2.4     0.4     2.3

Kittery Formation
  K-1                     0.8     4.3     1.0     2.7     0.4     2.4
  K-4                     1.1     4.9     1.1     2.6     0.3     2.0
  K-6                     1.0     5.2     1.2     3.1     0.5     3.2
  K-9                     1.0     5.3     1.2     3.1     0.5     2.8
  K-11                    0.9     4.9     1.2     2.9     0.5     2.9
  K-12                    1.0     4.9     1.1     2.9     0.4     2.7

Berwick Formation
  B-1                     1.0     5.1     1.1     3.2     0.5     3.0
  B-2                     1.1     5.5     1.3     3.4     0.5     3.4
  B-3                     1.3     6.5     1.5     3.8     0.6     3.7
  B-4                     1.0     5.1     1.2     3.2     0.5     2.9
  B-5                     0.9     4.7     1.1     2.9     0.5     2.6
  B-6                     1.1     5.3     1.2     3.2     0.5     2.9
  B-8                     0.7     3.9     0.9     2.7     0.4     2.7
  B-9                     1.0     5.1     1.1     3.1     0.4     2.9

Sample                    Lu       Zr    Hf       Y    Nb     Ta    Th

Carrabassett Formation
  H-2                     0.4    442.0    11    26.0     9           15
  H-3                     0.2    315.0     4    32.0    17           10
  H-5                     0.1    259.0     3    22.0    10           13
  H-6                     0.1    249.0     3    22.0    12            9
  H-7                     0.4    267.0     7    23.0    13            8
  H-8                     0.3    302.0     3    33.0    16            9
  H-9                     0.2    229.0     3    32.0    16            6
  H-10                    0.6    306.0     8    39.0    17            7
  H-11                    0.4    371.0    10    29.0    10           11
Rangeley Formation
  R-2-1                   0.5    301.0     7    35.0    14           11
  R-2-2                   0.4    263.0     5    22.0    13           10
  R-3-1                   0.3    265.0     5    27.0    16           11
  R-3-2                   0.4    252.0     5    24.0    15           10
  R-5-1                   0.3    291.0     7    25.0    18           16
  R-5-2                   0.5    189.0     4    41.0    22           18
  R-6-1                   0.4    355.0     7    24.0    15           11
  R-6-2                   0.4    290.0     6    26.0    14           10
  R-6-3                   0.4    273.0     6    30.0    14            8

Madrid Formation
  H-12                    0.4    234.0     6    28.0    13            8
  H-13                    0.4    282.0     7    23.0    13           11
  H-14                    0.4    206.0     6    27.0    13            8
  H-15                    0.4    237.0     6    28.0    13           12
  H-16                    0.3    174.0     2    36.0    16            2
  H-19                    0.3    166.0     5    25.0    10           11
  H-20                    0.3    166.0     4    23.0    12            7

Eliot Formation
  E-1                     0.5    430.0    14    31.0    10    0.5    10
  E-2                     0.6    516.0    17    33.0    12    0.5    13
  E-3                     0.4    157.0     5    24.5    11    0.5    11
  E-4                     0.3    183.5     6    22.0    10    0.5     9

Kittery Formation
  K-1                     0.3    157.5     5    24.5    10    0.5     8
  K-4                     0.3    201.0     6    24.0    45    3.5     3
  K-6                     0.4    163.0     5    27.0    13    1.0    13
  K-9                     0.4    164.0     6    28.5    11    0.5    10
  K-11                    0.4    264.0     9    28.0    10    0.5     8
  K-12                    0.4    221.0     7    26.0    11    0.5     9

Berwick Formation
  B-1                     0.5    316.0    10    29.0    11    0.5    10
  B-2                     0.5    297.0    10    30.0    13    1.0    11
  B-3                     0.6    428.0    14    35.0    14    0.5    15
  B-4                     0.4    197.0     7    28.5    12    0.5    11
  B-5                     0.4    171.0     6    26.5    11    1.0     8
  B-6                     0.4    210.0     7    30.5    11    0.5    10
  B-8                     0.4    242.0     8    23.0    12    0.5    11
  B-9                     0.4    233.0     8    28.0    10    0.5    10

Sample                      U    Pb    Sc     Cr      Co     Ni     Cu

Carrabassett Formation
  H-2                             14     0     58    11.0     24      3
  H-3                             10    15     90     7.5     41     14
  H-5                             17     0     55     3.5     21     11
  H-6                             16     9     73     8.5     34     36
  H-7                             14    11     77    16.5     33     32
  H-8                             10    15     97     4.0     43     13
  H-9                             27    18    126    12.0     69     33
  H-10                            17    15    104    17.5     49      7
  H-11                            27     0     64     8.5     28     14
Rangeley Formation
  R-2-1                    2.0    14    13     73    44.0     37     37
  R-2-2                    1.7    21    12    6.5    29.0     37     37
  R-3-1                    2.6    21    13     68    43.0     33     33
  R-3-2                    1.4    16    12     71    40.0     40     40
  R-5-1                    2.5    28    16     66    29.0     27     27
  R-5-2                    4.2    35    20     92    10.0     25     25
  R-6-1                    1.8    21    15     70    23.0     38     20
  R-6-2                    2.0    20    13     66    46.0     41     27
  R-6-3                    2.2    14    10     59    30.0     30    149

Madrid Formation
  H-12                            15    13    142    13.5     61     13
  H-13                            16    14    151    13.0     53     11
  H-14                            12    11     60    12.0     28      8
  H-15                            15    14    121    13.0     47     13
  H-16                            16    23    192    12.5    112     55
  H-19                            17     9     74     8.5     27      4
  H-20                            14    13     87    12.0     49     10

Eliot Formation
  E-1                      3.0    10    12           11.5     65     15
  E-2                      3.5    15    14           11.5     70     25
  E-3                      3.0    20    17           24.0    125     35
  E-4                      2.5    20    15           16.0     85     25

Kittery Formation
  K-1                      2.5    70    12           14.5     90     25
  K-4                      1.5     5    19           36.0     55    160
  K-6                      3.5    15    19           25.0    145      5
  K-9                      3.0     5    13           16.0     85     20
  K-11                     2.0    20    14           12.5     75     15
  K-12                    2.11    10    13           14.5     90     30

Berwick Formation
  B-1                      3.0    30    13           13.0     70     20
  B-2                      4.0    15    14           15.0     80     20
  B-3                      3.0    20    12           14.0     75     15
  B-4                      2.5    30                 21.0     80     30
  B-5                      2.5    25    13           14.0     80     35
  B-6                      3.0    15    13           15.0     85     45
  B-8                      2.5    45    18           18.5     65     30
  B-9                      3.0    15    12           15.0     85     20

Sample                    Zn    Ga

Carrabassett Formation
  H-2                      53     6
  H-3                      90    17
  H-5                      57     8
  H-6                      77    11
  H-7                      74    12
  H-8                      76    16
  H-9                     106    20
  H-10                     86    17
  H-11                     74     7
Rangeley Formation
  R-2-1                    99    17
  R-2-2                    86    19
  R-3-1                    98    20
  R-3-2                   101    20
  R-5-1                    90    21
  R-5-2                   116    31
  R-6-1                   101    16
  R-6-2                   106    14
  R-6-3                    75    17

Madrid Formation
  H-12                     59    14
  H-13                     65    15
  H-14                     66    18
  H-15                     60    15
  H-16                    115    26
  H-19                     40    12
  H-20                     66    16

Eliot Formation
  E-1                      55    11
  E-2                      60    12
  E-3                     110    20
  E-4                      45    15

Kittery Formation
  K-1                     110    16
  K-4                     120    24
  K-6                      80    24
  K-9                      55    16
  K-11                     50    12
  K-12                     65    15

Berwick Formation
  B-1                      50    13
  B-2                      60    15
  B-3                      60    15
  B-4                      95    19
  B-5                      70    14
  B-6                      55    16
  B-8                      95    19
  B-9                      60    15

Table 2. Merrimack Trough Nd and Sr Isotopic Compositions.

Sample    Sm (PPm)    Nd (PPm)    [sup.147]Sm/[sup.144]Nd

B-1         6.30        31.41              0.1212
B-3         7.96        40.88              0.1177
B-6         6.63        31.83              0.1260
B-9         6.07        30.12              0.1218
E-1         6.36        32.58              0.1181
E-3         5.07        25.85              0.1185
K-6         7.26        37.29              0.1177
K-9         6.16        30.49              0.1221
K-11        5.47        27.03              0.1224

Sample    [sup.143]Nd/[sup.144]Nd    [E.sub.Nd] (0 Ma)

B-1               0.512058                 -11.3
B-3               0.512015                 -12.2
B-6               0.512008                 -12.3
B-9               0.512069                 -11.1
E-1               0.511977                 -12.9
E-3               0.511999                 -12.5
K-6               0.511981                 -12.8
K-9               0.511969                 -13.1
K-11              0.512000                 -12.4

Sample    [E.sub.Nd] (420 Ma)    [T.sub.DM]    Rb (PPm)

B-1               -7.3              1.62           74
B-3               -7.9              1.63           94
B-6               -8.5              1.80           89
B-9               -7.1              1.61           82
E-1               -8.7              1.70           74
E-3               -8.3              1.67          130
K-6               -8.6              1.68          168
K-9               -9.1              1.79          117
K-11              -8.5              1.74           65

Table 3. LA-ICPMS Detrital Zircon Data for the Carrabassett Formation,
Maine.

Analyses    [sup.207]Pb/    [+ or -]   [sup.206]Pb/    [+ or -]  Rho
              [sup.235]U   1 [sigma]     [sup.238]U   1 [sigma]

de07A08           0.8252      0.0178         0.0977      0.0016  0.38
de07A09           1.6447      0.0319         0.1604      0.0046  0.73
de07A15           3.3177      0.2401         0.2340      0.0051  0.15
de07A20           1.9294      0.0333         0.1882      0.0027  0.42
de07A23           1.6611      0.0519         0.1685      0.0026  0.24
de07A24           2.2732      0.0631         0.2066      0.0040  0.35
de07A27           4.1297      0.1255         0.2870      0.0037  0.21
de07A28           0.9483      0.0157         0.1082      0.0012  0.33
de07A33           2.2759      0.0832         0.2010      0.0053  0.36
de07A34           0.7311      0.0387         0.0896      0.0026  0.27
de07A35           0.8828      0.0414         0.1018      0.0035  0.36
de07A51           3.1574      0.1283         0.2591      0.0115  0.55
de07A52           0.6643      0.0143         0.0872      0.0012  0.33
de07A57           2.6483      0.0849         0.2226      0.0049  0.34
de07A58           1.5951      0.0505         0.1629      0.0025  0.24
de07A59           9.6986      0.2020         0.4384      0.0056  0.31
de07A61           1.6287      0.0482         0.1687      0.0034  0.34
oc02a08           2.6505      0.1441         0.2165      0.0126  0.7947
oc02a09           2.2853      0.1415         0.2130      0.0107  0.6878
oc02a13           1.9623      0.1002         0.1871      0.0084  0.7302
oc02a16           3.3807      0.2466         0.2656      0.0119  0.7048
oc02a17           1.9400      0.1105         0.1702      0.0111  0.8114
oc02a18           2.3298      0.1854         0.2114      0.0102  0.5965
oc02a19           2.4207      0.1340         0.2116      0.0118  0.8149
oc02a20           2.0020      0.1027         0.1862      0.0087  0.6576
oc02a24           2.5732      0.1123         0.2149      0.0079  0.7052
oc02a25           6.8820      0.5480         0.3642      0.0350  0.9065
oc02a32           0.4436      0.0608         0.0660      0.0039  0.5269
oc02a33           0.5877      0.0489         0.0715      0.0048  0.7225
oc02a34           0.9561      0.0655         0.1043      0.0062  0.7499
oc02a37           0.9984      0.1332         0.1143      0.0118  0.8701
oc02a39           0.8848      0.0621         0.0961      0.0061  0.674
oc02a46           0.8416      0.0651         0.0950      0.0062  0.7173
oc02a47           2.5768      0.2926         0.2017      0.0247  0.8104
oc02a48           1.4787      0.1459         0.1513      0.0128  0.7572
oc02a54           2.3666      0.0973         0.1963      0.0078  0.6711
oc02a62           8.0972      0.3297         0.4137      0.0145  0.8406
oc02b03           4.6092      0.2345         0.3143      0.0125  0.9084
oc02b04           3.5973      0.9486         0.2772      0.0381  0.6823
oc02b06           2.6590      0.2839         0.2268      0.0132  0.6439
oc02b12           2.2238      0.0936         0.1959      0.0072  0.8044
oc02b14           4.1626      0.4077         0.2866      0.0271  0.963
oc03a05           0.9035      0.0408         0.1058      0.0034  0.7269
oc03a07           1.8559      0.0943         0.1749      0.0079  0.8471
oc03a08           3.2204      0.1598         0.2627      0.0103  0.916
oc03a11          11.3083      0.6306         0.4939      0.0307  0.9545
oc03b04           0.6002      0.0289         0.0777      0.0020  0.4382
oc03b05           1.1466      0.0504         0.1312      0.0037  0.5195
oc03b08           2.0178      0.1708         0.1936      0.0135  0.9342

Analyses       [sup.207]Pb/    [+ or -]      [sup.206]Pb/    [+ or -]
            [sup.235]U (Ma)   1 [sigma]   [sup.238]U (Ma)   1 [sigma]

de07A08               610.9         9.9             601.1         9.3
de07A09               987.5        12.3             959.1        25.4
de07A15              1485.2        56.5            1355.3        26.5
de07A20              1091.3        11.5            1111.7        14.8
de07A23               993.8        19.8            1003.6        14.1
de07A24              1204.0        19.6            1210.6        21.2
de07A27              1660.2        24.8            1626.5        18.4
de07A28               677.2         8.2             662.6         7.0
de07A33              1204.8        25.8            1180.8        28.6
de07A34               557.2        22.7             552.9        15.4
de07A35               642.5        22.3             625.1        20.2
de07A51              1446.8        31.3            1485.3        58.8
de07A52               517.2         8.7             538.8         7.2
de07A57              1314.2        23.6            1295.4        25.8
de07A58               968.3        19.8             972.9        13.8
de07A59              2406.6        19.2            2343.4        25.1
de07A61               981.4        18.6            1005.0        18.6
oc02a08              1314.8        40.1            1263.5        66.9
oc02a09              1207.7        43.7            1244.7        57.0
oc02a13              1102.7        34.3            1105.7        45.4
oc02a16              1499.9        57.2            1518.6        60.6
oc02a17              1095.0        38.2            1013.1        61.3
oc02a18              1221.4        56.5            1236.1        54.4
oc02a19              1248.8        39.8            1237.4        62.9
oc02a20              1116.2        34.7            1100.9        47.0
oc02a24              1293.1        31.9            1254.9        41.7
oc02a25              2096.3        70.6            2002.2       165.2
oc02a32               372.8        42.8             412.2        23.9
oc02a33               469.4        31.3             445.3        28.8
oc02a34               681.3        34.0             639.8        36.4
oc02a37               703.0        67.7             697.6        68.3
oc02a39               643.6        33.5             591.2        36.0
oc02a46               620.0        35.9             584.8        36.6
oc02a47              1294.1        83.1            1184.7       132.6
oc02a48               921.7        59.8             908.2        71.7
oc02a54              1232.6        29.3            1155.3        41.8
oc02a62              2241.9        36.8            2231.6        66.3
oc02b03              1750.9        42.5            1761.6        61.3
oc02b04              1548.9       209.5            1577.2       192.5
oc02b06              1317.2        78.8            1317.6        69.3
oc02b12              1188.6        29.5            1153.3        39.0
oc02b14              1666.7        80.2            1624.4       135.5
oc03a05               653.6        21.8             648.4        19.6
oc03a07              1065.5        33.5            1039.3        43.2
oc03a08              1462.1        38.5            1503.9        52.4
oc03a11              2548.9        52.0            2587.4       132.7
oc03b04               477.4        18.3             482.6        12.0
oc03b05               775.6        23.9             794.8        21.2
oc03b08              1121.5        57.5            1141.1        72.9

Analyses    [sup.207]Pb/    [+ or -]       [sup.207]Pb/    [+ or -]
             [sup.206]Pb   1 [sigma]   [sup.206]Pb (Ma)   1 [sigma]

de07A08           0.0614      0.0013              654.9        45.6
de07A09           0.0733      0.0018             1021.2        45.9
de07A15           0.1041      0.0061             1498.9       107.6
de07A20           0.0767      0.0011             1113.3        29.3
de07A23           0.0732      0.0022             1020.8        61.0
de07A24           0.0825      0.0013             1257.5        31.6
de07A27           0.1069      0.0025             1646.9        42.7
de07A28           0.0663      0.0009              714.5        29.3
de07A33           0.0846      0.0032             1307.3        73.9
de07A34           0.0626      0.0017              595.8        58.8
de07A35           0.0623      0.0031              683.0       104.5
de07A51           0.0906      0.0052             1438.0       110.1
de07A52           0.0570      0.0012              591.1        45.4
de07A57           0.0893      0.0025             1409.8        52.9
de07A58           0.0739      0.0021             1039.6        57.4
de07A59           0.1659      0.0019             2516.2        19.5
de07A61           0.0723      0.0026              994.0        72.6
oc02a08           0.0814      0.0012             1230.3        29.6
oc02a09           0.0775      0.0015             1135.2        39.5
oc02a13           0.0749      0.0011             1066.5        30.4
oc02a16           0.0950      0.0014             1527.7        27.7
oc02a17           0.0746      0.0014             1056.9        37.6
oc02a18           0.0827      0.0019             1262.4        44.8
oc02a19           0.0787      0.0011             1165.4        28.5
oc02a20           0.0741      0.0015             1044.7        41.8
oc02a24           0.0828      0.0014             1263.4        32.4
oc02a25           0.1298      0.0013             2094.8        18.0
oc02a32           0.0545      0.0016              390.4        65.8
oc02a33           0.0558      0.0011              445.8        42.6
oc02a34           0.0621      0.0011              678.7        38.1
oc02a37           0.0621      0.0010              677.4        33.3
oc02a39           0.0603      0.0014              615.6        49.9
oc02a46           0.0581      0.0013              533.1        48.8
oc02a47           0.0853      0.0020             1322.2        45.8
oc02a48           0.0671      0.0015              840.4        48.1
oc02a54           0.0810      0.0013             1221.6        31.4
oc02a62           0.1390      0.0012             2214.8        15.3
oc02b03           0.1079      0.0008             1764.9        13.2
oc02b04           0.1044      0.0020             1704.4        35.9
oc02b06           0.0874      0.0015             1369.5        32.6
oc02b12           0.0799      0.0008             1194.1        19.9
oc02b14           0.1035      0.0007             1688.7        13.3
oc03a05           0.0629      0.0007              703.3        23.0
oc03a07           0.0765      0.0008             1106.9        20.5
oc03a08           0.0927      0.0006             1481.5        12.3
oc03a11           0.1671      0.0009             2528.5         9.0
oc03b04           0.0561      0.0010              458.1        39.2
oc03b05           0.0648      0.0012              766.5        39.5
oc03b08           0.0798      0.0007             1191.1        18.4

Analyses        %
            conc.

de07A08        92
de07A09        94
de07A15        90
de07A20       100
de07A23        98
de07A24        96
de07A27        99
de07A28        93
de07A33        90
de07A34        93
de07A35        92
de07A51       103
de07A52        91
de07A57        92
de07A58        94
de07A59        93
de07A61       101
oc02a08       103
oc02a09       110
oc02a13       104
oc02a16        99
oc02a17        96
oc02a18        98
oc02a19       106
oc02a20       105
oc02a24        99
oc02a25        96
oc02a32       106
oc02a33       100
oc02a34        94
oc02a37       103
oc02a39        96
oc02a46       110
oc02a47        90
oc02a48       108
oc02a54        95
oc02a62       101
oc02b03       100
oc02b04        93
oc02b06        96
oc02b12        97
oc02b14        96
oc03a05        92
oc03a07        94
oc03a08       102
oc03a11       102
oc03b04       105
oc03b05       104
oc03b08        96

Fig. 11. Matrix diagram showing matches between the bulk-rock major
and trace element characteristics, bulk-rock Nd isotopic values, Nd
model ages, and detrital zircon ages of the Carrabassett Formation and
Ganderia. Carrabassett Forma tion paleocurrent indicators reflect an
outboard source. Although some of these parameters also match other
terranes, one or more mismatches complicate either Avalonia or
Laurentia as sources.

                                   Bulk-rock
                  Paleocurrent    Major/Trace     Bulk-rock
                   Indicators       Elements     Nd Isotopes

Ganderia               X               X              X
Juvenile               X               --             --
Avalonia
Avalonia               X               X              X
Supracrustals
Laurentia              --              X              X

                 Nd Model    Detrital
                   Ages       Zircons

Ganderia             X           X
Juvenile            --
Avalonia
Avalonia             X          --
Supracrustals
Laurentia            X          --
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Article Details
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Author:Dorais, Michael J.; Wintsch, Robert P.; Nelson, Wendy R.; Tubrett, Michael
Publication:Atlantic Geology
Article Type:Report
Geographic Code:1CANA
Date:Jan 1, 2009
Words:17105
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