Geomorphic Evolution of Coastal Dune Fields in the Northeastern Part of the Lake Michigan Basin: The Relationship to Lake Levels and Isostatic Rebound.
Alan F. Arbogast, Michigan State University, Department of Geography, George W. Monaghan, Indiana University, William A. Lovis, Michigan State University, Department of Anthropology
Coastal sand dunes are very common around Lake Michigan. Abundant research demonstrates that dunes along the southeastern shore of the lake began to form ~ 5 ka during the Nipissing stage of Lake Michigan Since that time the dunes enlarged episodically with several distinct periods of stability indicated by buried soils. Blowouts have also formed in many dunes, resulting in distinct parabolic landforms oriented to the west/northwest.
Current research in the northeastern part of the Lake Michigan basin indicates a different geomorphic history. Compared to the southern shore, Nipissing dunes are rare in the north and eolian landforms apparently grew horizontally rather than vertically. In the north, most major eolian deposition began after about ~ 3.2 ka and relates to a series of late Holocene lake transgressions. Large ( ~ 30-m high) dune ridges initially formed that rarely contain buried soils These ridges are now far inland because subsequent transgressions built lower dunes shoreward. This pattern occurs because older beaches and dunes were isostatically raised during intervening regressions, which exposed progressively younger surfaces on which dunes could grow. Several periods of dune growth have been identified during the late Holocene, including a widespread event at ~ l ka.
Loess Deposits and Lake Algonquin Spits in the Upper Great Lakes Region Support a Glacial Anticyclone at Circa 13-11 ka. Randall Schaetzl, Michigan. State University, Department of Geography and Frank Krist, U.S. Forest Service, Fort Collins, CO
Paleoclimate, models have, for many years, postulated that a large glacial anticyclone existed in and around the retreating Laurentide ice sheet, particularly in summer. This anticyclone, strengthened by the cold, dense air above the ice sheet, led to a narrow but potentially strong band of easterly winds near the ice margin. Until now, only the work of Krist and Schaetzl (2001), who identified long, west-east trending spits in northern Lower Michigan associated with Glacial Lake Algonquin (ca. 12.4 cal yrs ago), has provided the geomorphic data necessary to verify this anticyclonic circulation. In this paper, we present new geomorphic and sedimentologic data that corroborate our earlier work, and argue that these data are also in support of a strong glacial anticyclone at ca. 13-11 ka in the northern Great Lakes region.
Our geomorphic data consist of, first, a large, prominent spit on the Garden Peninsula, which must have formed in Glacial Lake Algonquin. This spit trends for almost 13 km in a SW direction, off a newly discovered island in Glacial Lake Algonquin. We herein name this feature Garden Island. The spit was mainly formed on E or NE winds which were probably quite strong, based on its size. Glacial Lake Algonquin drained ca. 11.9 ka, providing a minimum limiting age for the spit, and the associated atmospheric circulation. Second, we report on thick loess in NE Wisconsin and Iron County, Michigan, roughly 175 km to the west-northwest of Garden Island. In this area, a series of N-S trending moraines (comprised of silty and loamy tills) and associated outwash plains served as loess sources. Loess in this region is especially thick to the west of these major moraines, suggestive of a strong easterly wind component at the time of deposition. OSL ages on this loess generally fall within the period of Glacial Lake Algonquin, at 14.6-12.9 ka.
Together, these data suggest that easterly winds were a major component of the atmospheric circulation in the Great Lakes region during the Late Pleistocene ca. 14-11 ka. By the end of this time window, the margin of the Laurentide ice sheet, although highly lobate and irregular, lay across the Upper Peninsula. These data, therefore, add to the increasing pool of evidence for a strong glacial anticyclone in this region.
Evidence for Fire-Induced, Aeolian Sediment Redistribution in a Sandy, Hummocky Landscape near Evart, Michigan. Trevor Hobbs and Randy Schaetzl, Michigan State University, Department of Geography
In the sandy interlobate uplands of Osceola County, north of Evart, Michigan, there exist many dry, topographically closed basins (glacial kettles) containing a ~ 1 m thick sequence of silty sediment in the bottom of the depression. Silty deposits in these kettle bottoms are anomalous with respect to the preponderance of sandy drift in this region. The purpose of this research was to determine the most likely geomorphic origin for the silt, and assess its paleoenvironmental importance. Two possible hypotheses explaining the origin of the silt were tested: (1) the silt was winnowed from the surrounding upslope sediments over time, and concentrated in kettle bottoms via slopewash, and (2) the silt is loess (aeolian silt), blown into kettles and spatially concentrated in their bottom-centers. To evaluate these two hypotheses, sediments in 53 kettle bottoms and adjacent backslopes were sampled to characterize and compare their particle size distributions. The silt mineralogy of four kettle bottom-backslope pair sites was also compare d, to determine if the kettle bottom silt, is local or extra-regional. Additionally, eight kettle bottoms were depth-sampled to reconstruct their depositional histories, and charcoal fragments within buried soils in kettle bottoms were radiocarbon dated to determine the timing of silt deposition vis-a-vis soil formation. The combined evidence suggests that the silt, was locally redistributed by wind and preferentially deposited in kettle bottoms during former dry periods of increased local forest fire activity during the early and mid-Holocene. These data provide a new and potentially important paleoenvironmental proxy for recently glaciated landscapes, and highlight the point that episodic periods of dryness and landscape instability permeated the post-glacial period in Michigan.
The Slagle Delta: Field Evidence for a Previously Unrecognized Proglacial Lake and Its Relationship to Glacial Lake Chicago. Kevin A. Kincare, U.S. Geological Survey, Reston, VA
Field work in Wexford and Manistee Counties, Michigan, has revealed a large delta in the Manistee River valley originating on the inner (west) flank of the Lake Border moraine, near the confluence of the Lake Michigan lobe and the Traverse Bay sublobe of the Laurentide glacier. The Slagle delta is the largest of four deltas that laterally coalesce and have deltaic deposits up to .315 meters altitude. Existing surficial geologic maps have described this area as an outwash plain.
Glacial Lake Chicago, Glenwood II phase, existed around 13,000 14C years B.P. during the Port Huron stadial with a northern shoreline controlled by the position of the Port Huron moraine. Distal deposits from Slagle delta are found onlapping the eastern (outer) margin of the Port Huron moraine, implying a time correlation. However, the observed surface altitude of the lake in which Slagle delta was deposited is much higher than the closest mapped shoreline of Glenwood II (201 meters in Pentwater, 75 km to the southwest). This lake, here named Glacial Lake Mesick, occupied over 500 km2, overflowing southward through outlets to the Pere Marquette River and thence to the Glenwood II level. Slagle delta received sediment from westbound drainage across the Lake Border moraine.
Beginnings Endings, and Coincidences - Geology in the New Century - 1908! Diane Baclawski, Michigan State University, Division of Science Mathematics Education
What was happening in geology one hundred years ago? The world, the United States and the sciences in general were all in a state of flux in 1908. So many discoveries were made in the first eight years of the new century - a situation that parallels the first eight year of this new millennium. This paper briefly discusses some of the many significant science events of 1908 - and how they influenced the development of the geological sciences for the next century. In 1908, the first analyses of the 1906 San Francisco Earthquake were presented, the Tunguska Meteorite struck Siberia and Robert Peary set off for the North Pole. The state and national geological surveys were engaged in mapping their areas and publishing detailed guides for the public. The Association of American State Geologists was founded in 1908 and Grand Canyon was designated a National Monument. Activities of individual geologists are profiled as well. Frank Taylor introduced his theory of continental drift in 1908 - the same year that J. Tuzo Wilson was born. The same year saw the death of Henri Becquerel discoverer of X-rays, the birth of Edward Teller, inventor of the hydrogen bomb, and the invention of the Geiger Counter.
Critical Analysis of the Grand Traverse Bay Mastodon Boulder: Not a Petroglyph. J. M. Zawiskie, Cranhrook Institute of Science, Bloomfield Hills, MI
A press release in September 2007 described the discovery of markings on the. surface of a submerged granite boulder on the floor of Grand Traverse Bay (GTB); interpreted as possible petroglyph of a mastodon--hunting scene. The find has continued to attract national and international attention in the popular media. The discoverers emphasize the provisional nature of their petroglyph hypothesis and the need for further study and confirmation by petroglyph experts, sending an appeal to the scientific community. A geological approach using photos of the GTB boulder available in the public domain allow the image to be placed in the entire context of the boulder's surface, demonstrating that markings identical to those that make up critical portions of the hypothesized image are repeated on other areas of the rock. face. They strongly resemble curved laminae, and other features in layered granites attributable to flow structures and other magmatic processes. Similar structures are documented by the author in a layered granite erratic located on Grosse He in southeast Michigan. The photographic evidence strongly supports the conclusion that there is nothing on the surface of the GTB boulder that cannot be readily attributed to natural processes and that the hypothesized image is not a petroglyph.
Insects, Volcanoes, and Asteroids: A Comparative Discussion of Three Recent Theories about Dinosaur Extinction. Danielle Linker, University of Michigan
Sixty-five million years ago, one of the most mysterious species of creatures vanished from our planet. Though many scientists and amateurs as well have contributed to solving this mystery, years of research and contemplation have still not provided a definite explanation as to why this phenomenon occurred. The mystery of the great dinosaur extinction has created a debate among scientists all over the world. In order to understand this debate, we will first take a look at some background information about dinosaurs and the history of their existence. We will then examine dinosaurs as a species and provide a time frame for when they became extinct. Finally, we will explore and compare several of the many theories that scientists have proposed in order to explain this phenomenon, including the asteroid impact theory, the volcanism theory, and the insect theory. Although we cannot provide a final answer to the question of dinosaur extinction, we can shed further light on this puzzling event from the past and its possible implications for the future.
University Students' Prior Knowledge about Particle Motion at P--wave Arrival. Suttida Rakkapao, Michigan State University, Department of Geological Sciences
Common wisdom and emerging research suggests that people have the least difficulty understanding phenomena that occur in their local environments. This suggests that people living far from tectonic plate boundaries, such as students in Michigan, will have more trouble understanding boundary-related processes such as earthquakes, than students who live near boundaries, such as in Thailand. This study reports on the prior knowledge of students in Thailand, with particular reference to students' models about particle motion when P-waves arrive. These models illustrate prior knowledge that significantly influences what and how students learn in classroom. The data were collected via conceptual open-ended questions designed by the researchers and through explanatory follow-up interviews. Participants (n = 171) were freshmen in science, engineering, agricultural, sciences, and medicine fields from a university in Thailand. Our study found that most students hold non-scientific conceptual models about P-waves. For example, most of the study subjects believed that particles in a medium spread in all directions, like water waves, when P-waves arrive. Other students believed that particles move forward with a sine wave motion at P-wave arrival and that particles travel together with the propagating wave energy to the final destination, Furthermore, some students' drawings reflected images that appear in common textbooks and educational websites, albeit with embedded alternative conceptions. Overall, less than one-quarter of these students hold the scientific model that particles in a medium vibrate in the same direction as the propagating wave energy when P-waves arrive, coupled with recognition that particles do not travel with the propagating energy. Recognizing the existence of this prior knowledge is vital to creating teaching strategies for conceptual change about particle motion and seismic energy, in particular, as well as earthquakes in general. These findings suggest that proximity to large-scale tectonic phenomena does not necessarily lead to better understanding. Ongoing investigation of Michigan students with identical assessment instruments will provide valuable comparison with a non--tectonic population.
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