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Lithostratigraphy, petrology and sedimentary facies of the Late Cretaceous- Palaeocene Ispikan Group, southwestern Makran, Pakistan.

Byline: Akhtar Muhammad Kassi, Aimal Khan Kasi, John McManus and Abdul Salam Khan

Abstract

An isolated outcrop, comprising a 300 m thick succession of the Late Cretaceous-Palaeocene Ispikan group, is exposed as a thrust-bound inlier within the Oligocene-Miocene succession of the Panjgur Formation, 3 km to the northeast of the Ispikan village, in south-western Makran, Pakistan. The group is divisible into two lithostratigraphic units; 1) the Late Cretaceous Ispikan group in lower part; comprising mudstone, shale, siltstone and sandstone; and 2) Palaeocene Ispikan Conglomerate in upper part; comprising very coarse pebbly sandstone and conglomerate.

The Ispikan conglomerate is composed of pebbles of a variety of igneous, sedimentary and metamorphic rocks. Sandstone also dominantly comprises igneous and metamorphic rock fragments. Detrital modes of the sandstone suggest a recycled orogenic source, most probably the Himalayan- Karakorum-Hindukush collision orogen.

The group comprises 9 distinct facies, organized as 2 facies associations including the inner-fan channel facies association and the basin-plain facies association, which were parts of the earliest fan system of the Khojak-Panjgur submarine fan complex.

The petrology and provenance of the Ispikan group resemble with those of the surrounding younger submarine fan succession of the Oligocene-Miocene Panjgur Formation, however, its stratigraphic and palaeogeographic relationship with the surrounding succession still remains speculative needing further investigation.

Keywords: Lithofacies; Detrital modes; Provenance; Makran accretionary wedge; Submarine fan complex.

1. Introduction

The Late Cretaceous-Palaeocene Ispikan group (Kassi et al., 2007) is exposed as an isolated thrust-bound inlier (1 km long, 300 m wide) comprising thick succession of sandstone, conglomerate, mudstone and shale, within the Oligocene-Miocene Panjgur Formation near the Ispikan village of the southwestern Makran, Pakistan (Fig. 1). The group is named (Kassi et al., 2007) to represent the Late Cretaceous Ispikan formation; comprising cream, purple and varicolored mudstone, shale, siltstone and sandstone in its lower part, and Palaeocene Ispikan Conglomerate (Hunting Survey Corporation, 1961); comprising thick bedded, very coarse pebbly sandstone and conglomerate in its upper part.

The succession is part of the emergent Makran Accretionary Wedge, which formed in response to the northward subduction of the oceanic crust of the Gulf of Oman under the southern margin of the Afghan Block of the Eurasian Plate (White and Clittgord, 1976; Farhaudi and Karig, 1977; Jacob and Quittmeyer,1979; White, 1979; Platt et al., 1985; Platt andLeggett, 1986; McCall, 2003). Fig. 1. Location and geological map of the Ispikan and surrounding area, showing studied localities.

The Hunting Survey Corporation (1961) mapped and briefly described the Palaeocene Ispikan Conglomerate in their reconnaissance report; however, they have not described the conformably underlying sandstone and shale succession. They have assigned a Palaeocene age to the Ispikan Conglomerate on the basis of its stratigraphic position, as its lower part, the Ispikan formation of Kassi et al. (2007), is of Late Cretaceous age. Stratigraphic and palaeogeographic relationship of the Ispikan group (Kassi et al., 2007) with the surrounding Oligocene-Miocene Panjgur Formation is enigmatic because its upper and lower contacts are thrusted (Hunting Survey Corporation,1961).

The present paper describes stratigraphy, petrology, facies and facies associations and provenance of the Late Cretaceous-Palaeocene Ispikan group (Kassi et al., 2007), compares it with

the surrounding Oligocene-Miocene Panjgur Formation and attempts to provoke discussion on its provenance, age and the importance of its palaeogeographic position. Bed thickness is categorized according to the classification scheme of Ingram (1954) and grain size according to the classification scheme of Wentworth (1922). Facies and their associations have been described and interpreted in view of the classification schemes of Mutti and Ricci Lucchi (1972), Walker and Mutti (1973), Walker (1978), Underwood and Bachman (1982) and Pickering et al. (1986).

2. Lithostratigraphy

Kassi et al. (2007) proposed the names Wakai and Ispikan groups for the Cretaceous-Palaeocene successions of the Ispikan-Wakai area of south- western Makran (Table 1). Lithostratigraphy of the Late Cretaceous Ispikan group is described below:

Point counting of the sandstone of the Ispikan group shows that they are mostly composed of extra-basinal grains of non- carbonate types and minor proportions of carbonate grains of both intra- and extra-basinal origins. They have an average composition of Qt52-F33-L15 (Table 3, Fig. 3a), which suggests derivation of the extra-basinal components from a recycled and mixed orogenic source (Dickinson and Suczek, 1979; Dickinson et al., 1983; Dickinson, 1985). The Qm-F-Lt plot (Table 3; Fig. 3b) of the sandstone samples shows that they fall into the fields of mixed and basement uplift source terrains. These plots, along with the list of rock fragments (Table 2), suggest that source area contained high- to low-grade metamorphic rocks, granitic intrusions and minor

proportions of basic volcanic and sedimentary successions. The averages Qp3-Lvm62-Lsm35 and Lm26-Lv65-Ls9 (Kassi et al., 2003) indicate the importance of the igneous and metamorphic source area along with a combination of magmatic arcs and ophiolites. The average PtMt90-Av7-Bv3 (Kassi et al., 2003), indicate that plutonic and metamorphic rocks were the dominant source contributors, whereas, a volcanic source terrain was contributing lesser quantities. The plots (Figs.3a and b) suggest that both sandstones of the Ispikan group and Panjgur Formation have comparable provenance of recycled and mixed terrains, most plausibly the Himalaya-Karakorum- Hindukush orogens and associated magmatic arcsof Kohistan and Chagai-Raskoh and Bela-Muslimbagh-Waziristan ophiolites. Fig. 3. (a) Qt-F-L plot of the sandstone samples of the Ispikan group and Panjgur Formation and (b) Qm- F-Lt plot of the sandstone samples of the Ispikan group and Panjgur Formation. Table 3. List of point-count parameters determined for classification of sandstone (after Dickinson andSuczek, 1979; Dickinson et al., 1983; Dickinson, 1985).

Qt = Qm + Qp###where###Qt = total quartzose grains

###Qm = monocrystalline quartz grains

###Qp = polycrystalline aphanitic quartzose grains

F=P+K###where###F###= total feldspar grains

###P###= plagioclase-feldspar grains

###K###= potassium-feldspar grains

Lt = Lm + Lv + Ls###where###Lt = total unstable aphanitic lithic grains

###Lm = metamorphic aphanitic lithic grains

###Lv = volcanic and hypabasal aphanitic lithic grains

###Ls = sedimentary aphanitic lithic grains + extrabasinal carbonate

###grains

L = Lvm + Lsm###where###Lvm = volcanic, hypabasal and metavolcanic aphanitic lithic grains

###Lsm = sedimentary and metasedimentary aphanitic lithic grains

PtMt = Pt+Mt###where###Pt = plutonic grains

###Mt = metamorphic grains

4. Facies

Nine distinct facies (Table 4) are identifiable within the Ispikan group, which are described below:

4.1. Isp-1 (Normally graded pebbly sandstone)

The normally graded pebbly sandstone (Isp-1) is the most common facies of the Ispikan Conglomerate (Table 4; Fig. 4). It comprises, thickly to very thickly (up to several meters thick) bedded, very coarse pebbly sandstone with or without the mudstone/siltstone intraclasts of the underlying succession. Clasts are generally pebbly and reach up to several centimetres in length. The sandstone is poorly sorted, matrix-supported, normally graded, have sharp erosive bases and generally gradational contacts with overlying facies. These characteristics resemble with facies A, A2.5 and "graded-bed" of Mutti and Ricci Lucchi (1972), Pickering et al. (1986) and Walker (1978), respectively, and indicate rapid grain-by- grain deposition from suspension with rapid burial.

4.2. Isp-2 (Stratified pebbly sandstone)

This is a common facies of the IspikanConglomerate (Table 4; Fig. 4), which comprises

thickly to very thickly bedded, very coarse pebbly sandstone (maximum clast size: 2cm) with erosive bases and normal grading from very coarse and pebbly to medium grained sandy texture towards top. It generally shows 30-40 cm thick solitary or composite sets of cross-bedding and parallel lamination (Figs. 2d and e). These characteristics resemble with the facies A and A2.7 of Mutti and Ricci Lucchi (1972) and Pickering et al. (1986), respectively, and indicate traction bed-load or traction carpet at the base of high-concentration turbidity current. Facies Isp-1 and Isp-2 are mostly, but not exclusively, related; Isp-2 gradationally overlies the Isp-1 and their combination represents the "graded-stratified bed" of Walker (1978).

4.3. Isp-3 (Normally graded conglomerate)

Isp-3 is also a commonly occurring facies of the Ispikan Conglomerate (Table 4; Figs. 2e and f), generally comprising well-sorted, clast supported, rounded to well rounded, pebble to boulder conglomerate. Average size of the clasts of various beds varies between 2 and 10 cm, whereas, their maximum clast sizes range between10 and 20 cm. Beds are generally normally graded, however, inverse grading may also be found in some beds. Their lower contacts are mostly sharp and erosive and upper contacts gradational with the overlying facies. Beds are mostly lenticular and range between 200 and 500 cm in thickness. These characters resemble with the A and A2.3 facies of the Mutti and Ricci Lucchi (1972) and Pickering et al. (1986), respectively, and indicate rapid deposition from high-concentration turbidity currents. Facies Isp-3 represents the "graded-bed" and "inversely-to- normally graded bed" of Walker (1978).

comprises massive, highly bioturbated, purple, red, brown and varicoloured mudstone and shale, which is very thinly to very thickly bedded with sharp upper and lower contacts and planar geometry. These characters resemble the facies G of Mutti and Ricci Lucchi (1972) and G1.1 and G1.2 of Pickering et al. (1986) respectively and indicate very slow accumulation by pelagic- hemipelagic settling.

4.4. Isp-4 (Disorganised conglomerate and pebbly sandstone)

This is the least commonly occurring facies of the Ispikan Conglomerate (Table 4; Figs. 2c, e and f). It comprises very thickly bedded, generally very poorly sorted, matrix supported and subrounded to rounded pebble conglomerate. Average size of gravel clasts in various beds varies between 2 and40 cm and maximum clast size reaches up to 110 cm. Beds generally do not show any grading. Lower contacts are mostly sharp and the upper contacts gradational with the overlying facies. Beds are irregular to lenticular and their thicknesses range between 200 and 500 cm. These characters resemble the facies A and A1.4 of the Mutti and Ricci Lucchi (1972) and Pickering et al. (1986), respectively, and indicate long-distance transport by debris flows and/or high-concentration turbidity currents and finally rapid collective deposition of a pebble-sand mixture. Facies Isp-4 represents the disorganized-bed of Walker (1978).

.7. Isp-7 (Very fine sandstone/siltstone- mudstone couplets)

This facies is mostly associated with the Isp-5 (biogenic cream coloured mudstone facies) (Table4; Fig. 2b). It comprises very thinly bedded, very fine sandstone/siltstone and mudstone couplets. Sandstone/siltstone beds have planar geometry, sharp bases, gradational tops and parallel- to cross-laminated (Tcde and Tde of Bouma, 1962).These characters resemble the facies D of Muttiand Ricci Lucchi (1972) and D2.2 and D2.3 of Pickering et al. (1986) respectively and indicate deposition by mixed low-concentration turbidity currents and hemipelagic sedimentation

4.5. Isp-5 (Biogenic cream coloured mudstone)

A commonly occurring facies in the Ispikan formation (Table 4; Fig. 2b) comprises massive to very finely laminated, very thinly to very thickly bedded and highly bioturbated biogenic mudstone of cream to white colour. Contacts with underlying and overlying facies are sharp to gradational. Beds are mostly planar and laterally continuous for long distances. These characters resemble the G and G2 facies of the Mutti and Ricci Lucchi (1972) and Pickering et al. (1986), respectively, and indicate deposition by mixed hemipelagic and very low concentration turbidity currents.

4.6. Isp-6 (Varicoloured mudstone and shale)

This is also a commonly occurring facies of the Ispikan formation (Table 4; Fig. 2b). It

4.8. Isp-8 (Very coarse sandstone-mudstone couplets)

This facies comprises very thick-bedded and very coarse-grained sandstone and mudstone couplets, which are normally graded (Table 4). The sandstone beds have sharp erosive bases, gradational tops, lenticular morphology and possess Tabcde sequences of Bouma (1962). These characters resemble the facies C of Mutti and Ricci Lucchi (1972) and C2.1 of Pickering et al. (1986), respectively, and indicate deposition by high-concentration turbidity currents.

4.9. Isp-9 (Exotic clasts in mudstone/siltstone matrix)

This facies comprises very thick-bedded layers containing disorganized exotic clasts of intra- and extra-basinal origins within a mudstone, siltstone or very fine sandstone matrix (Table 4). The units have sharp erosive bases and tops and irregular morphology. These characters resemble the facies F of Mutti and Ricci Lucchi (1972) and F1.1 of Pickering et al. (1986), respectively, indicating deposition by slumps or debris flows.

Table 4. Characteristics of the lithofacies observed in the Late Cretaceous-Palaeocene Ispikan group.

Litho-###Lithology###Sedimentary###Bouma###Bounding###Thickness###Geometry###Trace###Process of###Facies

facies###structures###divisions###surfaces###Fossils###deposition###codes of

codes###other

###workers

Isp-1###Pebbly###Normally###None###Sharp to###Very###Lenticular###Rare###Rapid grain by###A, A2.5,

###sandstone###graded sand,###erosive###thick, up###grain

###poorly sorted###base,###to several###deposition

###gradational###meters###from

###top###suspension,

###with rapid

###burial

Isp-2###Pebbly###Parallel- to###None###Sharp to###Very###Lenticular###Rare###Traction bed###A, A2.7

###sandstone###cross-###erosive###thick, up###load or traction

###stratified###base,###to several###carpet at the

###gradational###meters###base of a high-

###top###concentration

###turbidity

###current

Isp-3###Conglomerate###Normally###None###Sharp to###Very###Lenticular###Rare###Rapid###A, A2.3

###graded with /###erosive###thick, up###suspension

###without###base,###to several###from high

###reverse###gradational###meters###concentration

###grading at the###top###turbidity

###base###current

Isp-4###Conglomerate###Disorganised,###None###Sharp to###Very###Lenticular###Rare###High###A, A1.4

###to pebbly###poorly sorted###erosive###thick, up###to###concentration

###sandstone###with sandy###base,###to several###irregular###turbidity

###matrix###gradational###meters###currents or

###top###debris flows

###and finally

###rapid

###collective

###deposition of

###pebble-sand

###mixture

Isp-5###Biogenic###Massive to###Td, Te###Sharp###Very thin###Planer###Common###Mixed###G, G2

###mudstone###very finely###to very###hemipelagic to

###laminated,###thick###very low

###bioturbated###concentration

###turbidity

###currents

Isp-6###Purple,###Massive,###None###Sharp###Very thin###Planar###Common###Pelagic to###G, G1.1,

###brown, red###bioturbated###to Very###Hemipelagic###G1.2

###and###thick

###varicoloured

###shale

Isp-7###Very fine###Parallel and###Tcde,###Sharp###Thin to###Planar###Rare###Mixed low###D, D2

###sandstone###cross-###Tde###bases and###very thin###concentration###D2.3

###siltstone/muds###laminated###gradational###bedded###turbidity

###tone couplets###tops###currents and

###hemipelagic

###sedimentation

Isp-8###Very thick###Normally###Tabcde###Sharp###Very thick###Lenticular###Rare###High###C, C2.1

###bedded###graded###erosive###bedded###concentration

###sandstone###base and###turbidity

###shale couplets###gradational###currents

###top

Isp-9###Exotic clasts###Disorganized###None###Sharp###Very thick###Irregular###Rare###Slumps /###F, F1.1

###in mudstone-###bases and###bedded###debris flows

###sandstone###tops

###matrix

A modified after Mutti and Ricci Lucchi (1972), Pickering et al. (1986) and Walker (1978).

Fig. 4. Sedimentary log of the Ispikan group showing various facies exposed at the outcrop. Letters A, B, D and G refer to the facies codes of the Mutti and Ricci Lucchi (1972) and Pickering et al. (1986).

5. Facies associations

The facies described in the previous section are organized into the basin plain and inner-fan channel facies associations, which pertain to the Ispikan formation and Ispikan Conglomerate, respectively. Facies associations are described as under:

5.1. Inner-fan channel facies association

The inner-fan channel facies association, comprising the Ispikan Conglomerate, is represented by medium to very coarse pebbly sandstone and conglomerate characterized by combination of facies Isp-1, Isp-2, Isp-3 and Isp-4

Table 4; Fig. 4), which represent facies A of Mutti and Ricci Lucchi, (1972), disorganized beds, inversely- to normally-graded beds, graded beds and graded-stratified beds of Walker (1978) and facies A2.3, A2.5, A2.7 and A1.4 of Pickering et al. (1986). Facies Isp-9, representing facies F of Mutti and Ricci Lucchi (1972) and F1.1 of Pickering et al. (1986), is also present in the lower part of this association. However, its stratigraphic relationship to the rest of the association cannot be ascertained due to thrusting. The succession is organized into fining-upward couplets of conglomerate/very coarse pebbly sandstone and coarse to medium grained sandstone, which has erosive bases. Some structures, like the foreset beds and low-angle cross-lamination (Figs. 2d and e), within the coarse sandstone beds and their vertical organization and geometry resemble typically with the braided channel deposits. Such features may have formed by the migration of channel thalweg.

5.2. Basin-plain facies association

The basin-plain facies association, comprising the Ispikan formation, is represented mainly by alternations of biogenic cream and varicoloured pelagic and hemipelagic mudstone and shale interbedded with very thin-bedded sandstone/siltstone i.e. Bouma (1962) Tcde, Tde sequences of turbidites (Table 4). This association comprises Isp-5 to Isp-8 facies, representing facies G, D and C of Mutti and Ricci Lucchi (1972) and facies G1.1, G1.2 and G2 of Pickering et al. (1986), which is characteristic of the basin- floor environment.

6. Discussion

Thrust-bound inliers of the Cretaceous- Palaeocene age comprise minor proportion of the vast area of the Makran Accretionary Wedge. However, they make an important part of the geological history of the Makran area and their understanding is very important for proper understanding of the geotectonic history of the Makran Accretionary Wedge. The inliers in the study area and surroundings occur within the thick succession of the Late Eocene-Miocene Hoshab Shale and Panjgur Formation, which have not been studied/described since the reconnaissance report of the Hunting Survey Corporation (1961), however, the siliciclastic succession the Oligocene- Miocene Panjgur Formation has been studied (Critelli et al., 1990; Kassi et al., 2003; Grigsby et al., 2004; Kassi et al., 2007; Kassi et al., 2011).

The variety of rock fragments within the conglomerate and sandstone of the Ispikan group (Kassi et al., 2007; Tables 2-3; Figs. 2-3) suggests a source terrain comprising mostly high-grade metamorphic, acidic igneous and sedimentary rocks. The mineralogical composition of the sandstone indicates that they are mostly meta- sedimentary litharenites. Their quartzose nature and low percentage of feldspars supports the suggestion that sediments are from recycled source and their Qt-F-L plot (Fig. 3a) suggests a

collision orogen as the main source terrain for the sandstone. The Qm-P-K plot (Fig. 3b) shows that the sandstone has very high percentages of monocrystalline quartz (Qm), as compared to plagioclase (P) and K-feldspar (K), which provides additional evidence to suggest recycled siliciclastic detritus. We suggest that the most likely source is the Himalayan-Karakorum- Hindukush collisional orogen.

Sandstone of the surrounding Oligocene Panjgur Formation, exposed in a vast area of the Makran Accretionary Wedge, are also composed of high proportions of quartz and metamorphic, igneous and sedimentary rock fragments (Table2), which also have a recycled quartzose detrital mode (Critelli et al., 1990; Kassi et al., 2003; Grigsby et al., 2004).

Varieties of the rock fragments within the sandstone of the Panjgur Formation also suggest derivation from the

Himalayan-Karakorum-Hindukush orogen and associated suture belts, ophiolites, mACopyrightlanges and volcanic arcs. Qayyum and Naim (2001) consider the Himalayan orogenic belt as the most likely provenance for sandstone of the Khojak Formation of the Katawaz Basin of Pakistan and Afghanistan, which is the Oligocene-Miocene deltaic and shallow marine equivalent of the Panjgur Formation. They observed compositional and provenance changes within the succession of the Khojak Formation, which they related to the gradual uplift of the Himalayan orogen due to thrusting and progressive erosion of the elevated thrust sheets and unroofing of the Himalayan orogen. They have proposed that volcanic fragments within the sandstone of the Khojak Formation were derived from the Himalayan suture zone, where basic igneous rocks of the Kohistan Island Arc were also exposed. Their proposed palaeogeographic model also indicates the Bela-Muslimbagh ophiolites, and also perhaps the Kirther-Sulaiman belt, as the source area for their "Katawaz Delta" and "Khojak Submarine Fan". Critelli et al. (1990) imply that reworking of the co-eruptive products such as the Chaghai volcanic arc has produced volcanic detritus of the Panjgur sandstone. We propose a combined source of the Himalayan suture zone for the high- grade metamorphic and acidic igneous detritus and Bela-Muslimbagh ophiolites, and possibly the Chagai-Raskoh volcanic arc, for the basic/ultrabasic detritus.

We think that most of the low- to high-grade metamorphic, granitic and part of basic detritus have been derived from the Himalayan-Karakorum-Hindukush orogen, whereas part of the basic and ultrabasic detritus was derived from the Bela-Muslimbagh Ophiolites and Chaghai-Raskoh Volcanic Arc. Although ultrabasic material is not very common in the sandstone and conglomerate of the Ispikan and Panjgur formations, occasional grains of chrome spinel (picotite) and serpentinite suggest derivation from the ophiolitic belts.

Qayyum and Naim (2001) have shown that during Palaeogene only sedimentary and low- grade metamorphic rocks were exposed in the Himalayas, however, at a later stage, high-grade metamorphic rocks were also exposed and started contributing their detritus, a shift that may be attributed to the progressive unroofing of the Himalayas.

This notion does not fit with the composition of sandstone and conglomerate of the Late Cretaceous-Palaeocene Ispikan group and Oligocene-Miocene Panjgur Formation, which contain varieties of igneous and high-grade metamorphic fragments including gneisses and granites and indicate unroofing of the source area during the Early Palaeocene. In view of the remarkable similarities of petrology and provenance between the Late Cretaceous- Palaeocene Ispikan group and Oligocene-Miocene Panjgur Formation of the Makran Accretionary Wedge and Khojak Formation of the Katawaz Basin, we suggest that their detritus has been derived from similar source areas, most likely the Himalaya-Karakorum-Hindukush orogenic belt and associated ophiolitic and sedimentary belts (Kassi et al., 2003; Qayyum and Naim, 2001; Critelli et al., 1990).

Our data suggest that the early Himalayan- Karakorum-Hindukush orogenic highlands to the north and Kirther-Sulaiman belt to the east of the Katawaz remnant ocean had formed during the Early Palaeocene and has been shedding detritus ever since (Beck et al., 1995; Garzanti et al., 1996; Qayyum et al., 1996a, 1996b, 1997a, 1997b; Kassi et al., 2003). Siliciclastic sediments were dispersed to the Katawaz remnant ocean to form the Kkojak-Panjgur delta-submarine fan complex, which comprises the Late Eocene to Oligocene Khojak Formation in the Katawaz area, and the Late Cretaceous-Palaeocene Ispikan group and Late Eocene-Miocene succession of the Hoshab/Siahan shale and Panjgur Formation in the Makran area (Qayyum et al., 1996a, 1996b, 1997a, 1997b; Kassi et al., 2003). Longitudinal ridges and flute marks at the base of Ispikan Conglomerate, observed in one locality, show orientation of N 60W and flow direction towards NW, which is also compatible with the general palaeoflow trend of the Panjgur Formation (Kassi et al., 2011, 2013).

Facies and facies associations of the Late Cretaceous-Palaeocene Ispikan group indicate deposition in inner-fan channels and basin-floor, which were parts of the earliest submarine fan system of the complex. The Oligocene-Miocene Panjgur Formation was also deposited in a very large submarine fan complex, in which several fan components/facies associations of the submarine fan systems, such as middle-fan channels, outer- fan lobes, fan-fringe and basin-plain, are recognizable (Kassi et al., 2003; Kassi et al., 2011).

Although, the inner-fan channel facies were not observed in the studied sections of the Oligocene-Miocene Panjgur Formation it is anticipated that they are present east- northeastward in the proximal parts of the complex, which have not yet been studied. The dominant westward palaeocurrent pattern, as shown by the Panjgur succession (Kassi et al.,2003), is parallel to the regional trend and trench axis, which is characteristic of trenches where abyssal plains are incorporated into the accretionary wedges (Dickinson, 1982; Nilsen and Zuffa, 1982; De Roza et al., 1986; Lash, 1986,1987).

The "Khojak-Panjgur Submarine Fan Complex" has been interpreted as the present day analogue of the Indus Fan (Critelli et al., 1990; Qayyum et al., 1997a, 1997b; Kassi et al., 2003). Qayyum et al. (1996a) suggest that the Murgha Faqirzai and Shaigalu members of the Khojak Formation comprises subaqueous to subaerial facies typical of a fluvial-dominated and wave- modified delta that axially fed their "Khojak Submarine Fan" to the southwest. Kassi et al. (2003) proposed that the Ispikan and Panjgur successions were the further ocean-ward continuum of the Katawaz delta of Qayyum et al. (1997a, 1997b), which they named as the "Khojak-Panjgur Submarine Fan Complex". It developed in the Katawaz remnant ocean that existed between the Afghan Block of the Eurasian

Plate and the western margin of the Indian Plate and continued further south-westward in the Gulf of Oman abyssal plain. We support the notion of Critelli and De Rosa (1987) and Critelli et al. (1991) that sediment transport was mainly controlled by the Chaman-Ornach Nal Transform System and initially detritus was transported generally southwards along the Chaman-Ornach Nal Transform System and then turned westward and parallel to the present active margin of the Makran Accretionary Wedge.

Despite the age contrast and thrust-boundary relationship the Late Cretaceous-Palaeocene Ispikan group and Late Eocene-Miocene Panjgur Formation and Siahan Shale share the characters of being components of a submarine fan complex that had started to establish during the Early Palaeocene and continued to evolve during Palaeocene through Miocene. However, the stratigraphic relationship of the Ispikan group with the surrounding Oligocene-Miocene Panjgur Formation and palaeogeographic position of the Ispikan group is still enigmatic because of their thrust contacts. In the studied areas no flysch succession of Eocene age has been mapped, however, the Raskoh Flysch Belt located to north of the Mashkhel Trough, is older and may be the possible equivalent succession. Also westwards across the Iranian border McCall (2003) have mapped Early Eocene-Early Oligocene- Miocene flysch turbidites north of the town of Pishin. We propose that further detailed work, especially on biostratigraphy of both the formations, as well as the Raskoh Flysch Belt may be carried out in order to ascertain their stratigraphic relationship.

7. Conclusions

Sandstone and conglomerate of the Late Cretaceous-Palaeocene Ispikan group of the Makran Accretionary Belt are composed of high proportions of metamorphic, acidic igneous and lesser proportions of sedimentary rock fragments and shows a recycled detrital mode. Varieties of the rock fragments, especially of the high-grade metamorphic origins, within the conglomerate and sandstone, suggest that material was derived from the Himalayan-Karakorum-Hindukush orogen and associated suture belts, ophiolites, mACopyrightlanges and volcanic arcs. Their characters resemble with those of the surrounding succession of the

Oligocene- Miocene Panjgur Formation and the up-current deltaic equivalent, the Khojak Formation of the Katawaz Basin, which also indicates comparable detrital modes.

The Late Cretaceous-Palaeocene Ispikan group comprises nine distinct facies organized into the inner-fan channels and basin-plain facies associations of the submarine fan complex. The surrounding succession of the Oligocene-Miocene Panjgur Formation is also a deposit of a submarine fan complex, showing of the middle- to lower-fan and basin-plain facies associations/fan components.

Although the petrology, provenance and depositional environments of both the Ispikan group and Panjgur Formation are comparable, their stratigraphic relationship and palaeogeographic positions are still enigmatic, as the Ispikan group is an inlier having thrusted contacts with the Panjgur formation. Further biostratigraphic work is needed to establish their stratigraphic relationship and palaeogeographic positions.

Acknowledgements

Funding of AMK through a Commonwealth Postdoctoral Fellowship of the Commonwealth Scholarship Commission in the United Kingdom is gratefully acknowledged. We also acknowledge the Higher Education Commission of Pakistan for assistance to carry out fieldwork programs in the Makran area. Collaboration and encouragement of E. K. Walton is greatly appreciated.

References

Beck, R.A., Burbank, D.W., Sercombe, W.J., Riley, G.W., Barndt, J.K., Berry, J.R., Afzal, J., Khan, A.M., Jurgen, H., Metjee, J., Cheema, A., Shafique, N.A., Lawrence, R.D., Khan, M.A., 1995. Stratigraphic evidence for an early collision between northeast India and Asia. Nature, 373, 55-58.Bouma, A.H., 1962. Sedimentology of some flysch deposits: a graphic approach to facies interpretation. Elsevier, Amsterdam.Critelli, S., De Rosa, R., 1987. Composizione e proveneienza della areniti oligo-mioceniche della Formazione de Panjgur (Catena del Makran, Pakistan). Giornale di Geologia, 49,187-196.

Critelli, S., De Rosa, R., Platt, J.P., 1990.Sandstone detrital modes in Makran accretionary wedge, southwest Pakistan: implications for tectonic setting and long distance turbidite transportation. Sedimentary Geology, 68, 241-260.De Roza, R., Zuffa, G.G., Taira, A. Leggett, J.K.,1986. Petrology of trench sands from the Nankai Trough, southwest Japan: implications for long-distance turbidite transportation. Geological Magazine, 123, 477-486.Dickinson, W.R., 1982. Composition of sandstones in circum-Pacific subduction complexes and forearc basins. American Association of Petroleum Geologists Bulletin,66, 121-137.Dickinson, W.R., 1985. Interpreting provenance relations from detrital modes of sandstones, In: Zuffa, G.G. (Ed.), Provenance of Arenites. Reidel, Dordrecht, 333-361.Dickinson, W.R., Beard, L.S., Brakenridge, G.R., Erjavec, J.L., Ferguson, R.C., Inman, K.F., Lindberg, F.A., Ryberg, P.T., 1983. Provenance of the north American phanerozoic sandstones in relation to tectonic setting. Geological Society of AmericaBulletin, 94, 222-235.Dickinson, W.R., Suzek, C.A., 1979. Plate tectonics and sandstone composition. American Association of Petroleum Geologists Bulletin, 63, 2164-2172.Farhaudi, G., Karig, D.C., 1977. Makran of Iran and Pakistan - an active arc system. Geological Society of America Bulletin, 5,664-668.Garzanti, E., Critelli, S., Ingersoll, R.V., 1996.Palaeogeography and palaeotectonic evolution of the Himalayan Range as reflected by detrital modes of Tertiary sandstones and modern sands (Indus transect, India and Pakistan). Geological Society of America Bulletin, 108, 631-642.Grigsby, J.D., Kassi, A.M., Khan, A.S., 2004.Petrology and geochemistry of the Oligocene-Early Miocene Panjgur Formation and upper cretaceous-Palaeocene Ispikan formation and Wakai mACopyrightlange in the Makran Accretionary Belt, southwest Pakistan. Annual meeting Geological Society of America, Colorado, USA, Proceedings, 36 (5).

Hunting Survey Corporation, 1961.Reconnaissance Geology of part of west Pakistan: A Colombo plan cooperation project, Toronto, Canada.Ingram, R.L., 1954. Terminology of the thickness of stratification and parting units in sedimentary rocks. Geological Society of America Bulletin, 65, 937-938.Jacob, K.H., Quittmeyer, R.C., 1979. The Makran region of Pakistan and Iran: Trench-arcsystem with active plate subduction. In:Farah, A., DeJong, K.A. (Eds.), Geodynamics of Pakistan. Geological Survey of Pakistan,305-318.Kassi, A.M., Grigsby, J.D., Khan, A.S. Nicholson, K., 2003. Sandstone petrology of the oligocene-early miocene panjgur abyssal plain turbidites in Turbat-Ispikan area of the Makran Accretionary wedge, southwest Pakistan. 37th North Central Meeting, Geological Society of America, Kansas City, Missouri, USA, Proceedings, 23-25.Kassi, A.M., Grigsby, J.D., Khan, A.S., 2013.Sandstone petrology and geochemistry of the oligocene-early miocene Panjgur formation, Makran Accretionary wedge, southwest Pakistan: Implications for provenance, weathering and tectonic setting. Journal of Asian Earth Sciences (submitted).Kassi, A.M., Kelling, G., Khan, A.S. Kasi A.K.,2011. Facies and cyclicity within the oligocene-early miocene panjgur formation, khojak-Panjgur submarine fan complex, Southeast Makran, Pakistan. Journal of Asian Earth Sciences, 41, 537-550.Kassi, A.M., Khan, A.S. Kassi, A.K., 2007.Newly proposed cretaceous-palaeocene lithostratigraphy of the Ispikan-Wakai Area, southwestern Makran, Pakistan. Journal of Himalayan Earth Sciences, 40, 25-31.Lash, G.G., 1986. Anatomy of an early palaeozoic subduction complex in the central Appalachian orogen, Sedimentary Geology,51, 75-95.Lash, G.G., 1987. Longitudinal petrographic variations in a middle ordovician trench deposit, Central Appalachian orogen. Sedimentology, 34, 227-235.McCall, G.J.H., 2003. A critique of the analogy between archaean and phanerozoic tectonics based on regional mapping of the mesozoic- cenozoic plate convergent zone in Makran, Iran. Precambrian Research, 127, 5-17.Mutti, E., Ricci Lucchi, F., 1972. Le torbiditi dell' appennino settentrionale: introduzione all' analisi di facies. Memorie della Societa Geologica Italiana, 11, 161-199.Nilsen, T.H., Zuffa, G.G., 1982. The Chugach terrain, a cretaceous trench-fill deposit, southern Alaska. In: Leggett, J. K. (Ed.), trench-forearc Geology. Geological Society of London, Special Publication, 10, 213-227.Pickering, K., Stow, D., Watson, M., Hiscott, R.,1986. Deep-water facies, processes and models: A review and classification scheme for modern and ancient sediments. Earth- Science Reviews, 23, 75-174.Platt, J.P., Leggett, J.K., 1986. Large-scale sediment underplating in the Makran accretionary prism, southwest Pakistan. Geology, 13, 507-511.Platt, J.P., Leggett, J.K., Young, J., Raza, H., Alam, S., 1985. Stratal extension in thrusts of footwalls, Makran accretionary prism - implications for thrust tectonics. American Association of Petroleum Geologists Bulletin,70, 191-203.Qayyum, M., Lawrence, R.D., Niem, A.R., 1997a.Molasse-delta-flysch continuum of the Himalayan orogeny and closure of the palaeogene katawaz remnant ocean, Pakistan. International Geology Review, 39, 861-875.Qayyum, M., Lawrence, R.D., Niem, A.R., 1997b.Discovery of the palaeo-indus delta-fan complex. Geological Society of London Journal, 154, 753-756.Qayyum, M., Niem, A.R., Lawrence, R.D., 1996a.Newly discovered palaeogene deltaic sequence in Katawaz Basin, Pakistan, and its

tectonic implications. Geology, 24, 835-838. Qayyum, M., Niem, A.R. Lawrence, R.D., 1996b.Missing palaeogene Himalayan siliciclastic sediments found in Katawaz Basin, Pakistan. Geological Society of America Bulletin, Proceedings, 28, A-407.Qayyum, M., Niem, A.R., 2001. Detrital modes and provenance of the palaeogene Khojak formation in Pakistan: Implications for early Himalayan orogeny and unroofing. Geological Society of America Bulletin, 113,320-332.Underwood, M.B., Bachman, S.B., 1982.Sedimentary facies associations within subduction complexes. Geological Society of London, Special Publication, 10, 537-550.Walker R.G., Mutti, E., 1973. Turbidite facies and facies associations: In: Middleton, G.V., Bouma, A.H. (Eds.), Turbidites and deep- water sedimentation. Society of economic palaeontologists and mineralogists, pacific Section, short Course, Anaheim, 119-157.Walker, R.G., 1978. Deep-water sandstone facies and ancient submarine fans: models for exploration for stratigraphic traps. Bulletin American Association of Petroleum Geologists, 62, 932-966.Wentworth, C.K., 1922. A scale of grade and class terms for clastic sediments. The Journal of Geology, 30, 377-92.White, R.S., 1979. Deformation of the Makran continental margin. In: Farah, A., DeJong, K. A., (Eds.), Geodynamics of Pakistan. Geological Survey of Pakistan, 295-304.White, R.S., Klitgord, K., 1976. Sediment deformation and plate tectonics in the Gulf of Oman. Earth and Planetary Science Letters,32, 199-209.
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Publication:Journal of Himalayan Earth Sciences
Geographic Code:9PAKI
Date:Dec 31, 2013
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