Barry B. Miller

Chronologic evidence for multiple periods of loess deposition during the Late Pleistocene in the Missouri and Mississippi River Valley, United States: Implications for the activity of the Laurentide ice sheet

Abstract The loess stratigraphy of the mid-continental U.S. is an important proxy record for the activity of the Laurentide Ice Sheet in North America. One of the most outstanding problems is deciphering the age of loess deposits in this area during the late Pleistocene. Radiocarbon dating of snails and thermoluminescence dating of the fine-silt fraction (4–11 μm) from loess at the Loveland Loess type section, Loveland, Iowa and a recent excavation at the Pleasant Grove School section. Madison County, Illinois provide new chronologic control on loess deposition in the Mississippi/Missouri River Valley chronology indicates that the Loveland Loess is Illinoian in age (135±20 ka) but is not correlative with the Teneriffe Silt which is dated to 77 ± 8 ka. Concordant radiocarbon and thermoluminescence age estimates demonstrate that the Roxana Silt and a correlative loess in Iowa, the Pisgah Formation, is probably 40-30 ka old. These age estimates in conjunction with previous results indicate that there were four periods of loess deposition during the last 150 ka at 25-12 ka, 45-30 ka, 85-70 ka and at ca. 135 ± 20 ka. This chronology of loess deposition supports the presence of both a late Illinoian and early Wisconsinan loess and associated soils. Thus, there may be more than one soil in the loess stratigraphy of the mid-continental U.S. with morphologies similar to the Sangamon Soil. The last three periods of loess deposition may be correlative with periods of elevated dust concentrations recorded in the Dye 3 ice core from southern Greenland. This is particularly significant because both areas possibly had the same source for eolian particles. Reconstructions of atmospheric circulation for glacial periods show a southerly deflected jet stream that could have transported dust from the mid-continental USA to southern Greenland. Lastly, the inferred record of loess deposition is parallel to a chronology for deglaciation of the Laurentide Ice Sheet deciphered from chronologic and stratigraphic studies of raised glacial and marine sediments in the Hudson Bay Lowlands, Canada. These chronologies indicate that the Laurentide Ice Sheet was quite dynamic during the late Pleistocene, advancing and retreating across North America at least four times during the last 150 ka.

Late-glacial paleoenvironment of Lake Algonquin sediments near Clarksburg, Ontario

Excavation below the Lake Algonquin gravel beach bar near Clarksburg, Ontario, exposed mollusc-bearing clay over a lens of plant debris. This is the northernmost and most deeply buried Lake Algonquin fossil site found thus far in Ontario. It is the first site to provide dates from directly below the Algonquin beach bar. Two radiocarbon dates of about 11 200 years confirm the age of isostatically transgressing Lake Algonquin. Plant macrofossils (21 taxa), pollen (39 taxa), molluscs (12 taxa), and ostracodes (18 taxa) indicate that the climate was colder than present by several degrees and the forest-tundra ecotone was nearby initially but retreated northward rather quickly. Upward increases in abundances and diversity of molluscs and ostracodes suggest it was a time of rapid migration and colonization of species.

Late Quaternary mollusks from glacial Lake Algonquin, Nipissing, and transitional sediments from southwestern Ontario, Canada

Abstract Mollusks were studied from six sites in Lake Algonquin deposits (12,000-10,000 yr B.P.), five transitional (Lake Stanley low stage; 10,000 – 6000 yr B.P.), and six Nipissing stage sites (6000-4000 yr B.P.) east of Lake Huron in southwestern Ontario. The sites represent a variety of near-shore, lagoonal, estuarine, and fluvial environments. Eighteen species were limited to occurrences in Algonquin stage deposits; 8 were found only in the transitional age sites; and 14 species were restricted to Nipissing stage localities. With the possible exception of Goniobasis livescens , which occurred at five of the six Nipissing stage sites, the remaining stratigraphically limited species were usually restricted to one or two localities and probably cannot be used as zone fossils. Some cold-tolerant species (e.g., Anodonta grandis simpsoniana ) were very early migrants into the study area, while others arrived later, apparently from eastern, southern, and western sources. Mollusks proved useful in paleoenvironmental reconstructions and to a lesser extent in biostratigraphic zonation.

An early Holocene oxygen isotope record from the Olson buried forest bed, Southern Lake Michigan

Analysis of a 3.5 m vibracore from the Olson buried forest bed in the southern Lake Michigan basin provides new paleolimnological data for the early Holocene. The core records a rise in lake level from the Chippewa low water phase toward the Nipissing high water phase. Deepening of the water level at the core site is suggested by a trend toward decreasing organic carbon content up core that is interpreted as a response to increasing distance between terrestrial debris sources and the core site.Published data from deep water cores from the southern Lake Michigan basin suggest there had been an inflow of isotopically light water from glacial Lake Agassiz into the southern basin between 10.5-11 ka (A1 event). The data also indicate a second flood of isotopically light water between 8-9 ka (A2 event).Three new 14C dates from the Olson site core suggest that most of the sediment was deposited between 8.45 ka and 8.2 ka, an interval roughly coeval with the second pulse of 18O-depleted water (A2) from Lake Agassiz into the southern basin. Oxygen isotope ratio analysis of shell aragonite from the gastropods Probythinella lacustris and Marstonia deceptashows increasingly negative values up core. This trend inσ18O values suggests that 18O - depleted water entered the southern basin about 8.4 ka. The Olson site core thus provides a chronology of events in the southern Lake Michigan basin associated with the draining of glacial Lake Agassiz.

A 6000 year water level history of Europe Lake, Wisconsin, USA

Europe Lake occupies a small, closed, basin that would have been an embayment in Lake Michigan during the high water level events in the larger lake. Cores recovered from the lake reveal late Holocene water level fluctuations in the basin that are inferred from changes in taxa and abundance of molluscs, ostracodes, magnetic susceptibility, organic carbon, and oxygen isotopes.Non-glacial, Holocene lacustrine/paludal sedimentation in this portion of the Europe Lake basin started after 6600 RCYBP and was probably initiated by a rise in the water table of the deep bedrock aquifer, during the Nipissing transgression in Lake Michigan. Isotopically light ground water from this source was probably a major contributor during this phase to the negative δ18O spikes in Valvata tricarinata and Amnicola limosa.The start of stable lacustrine conditions is marked by maximum diversity of ostracode and mollusc taxa and a shift toward much more positive δ18O values. The Europe Lake basin at this time became an embayment of Lake Michigan. This event was probably coeval with the peak of the Nipissing transgression, when the water plane reached an altitude of about 183 m.The isolation of Europe Lake from Lake Michigan started at about 2390 RCYBP and is probably due to a drop in water level in Lake Michigan and/or to isostatic uplift of the Door Peninsula. Since isolation from Lake Michigan, water levels in Europe lake have been controlled primarily by fluctuations in local precipitation, evaporation and ground water discharge.

Pre-Late Wisconsinan Pleistocene biota from southeastern Michigan, U.S.A.

Abstract Fossiliferous sediments underlie the Late Wisconsinan Mill Creek and Fisher Road tills at the Mill Creek site northwest of Port Huron, Michigan. Fragmentary remains of 5 fish and 11 mammal taxa occur with 39 taxa of molluscs, 6 of ostracodes, and a pine-spruce pollen assemblage. While the fish are wide-ranging, the mammals include distinctly northern elements such as Dicrostonyx sp., Lemmus sp., Mictomys borealis, and Microtus xanthognathus. The molluscs include a mixture of cold (Vertigo alpestris oughtoni and V. modesta) and warm (Lioplax sulculosa) taxa. None of the vertebrates have been found at Michigan sub-till sites before, and Lioplax is new to Michigan, fossil or living. Vertigo hannai is known only as a Pleistocene fossil. At present the age of the biota is indeterminate. The stratigraphy indicates a Middle Wisconsinan or greater age. A finite 14C age of 48.3 ± 0.8 ka (QL-1215) was later supplemented by a TL date of 57 ± 9 ka, but perhaps as old as 300 ka. Two clusters of amino acid allo-isoleucine/isoleucine values obtained from six genera of molluscs are interpreted to represent the co-occurrence of early Sangamonian (AIle/Ile values ranging from approximately 0.15 to 0.25) and Illinoian (AIle/Ile values ranging from approximately 0.25 to 0.35) mollusc fossils at the Mill Creek site. These results highlight the need for more reliable Quaternary dating methods.

Holocene environmental changes in the Whitefish Dunes Area, Door Peninsula, Northern Lake Michigan Basin, USA

A two meter sediment core taken from an inter-dune pond in Whitefish Dunes State Park, Door Peninsula, Wisconsin, provides a record of paleoenvironmental changes in the area from approximately 3600 RCYBP to 5100 RCYBP. The hydrology of the Whitefish Dunes pond is now apparently dependent on ground water recharge from local precipitation that infiltrates into the dunes and from Clark Lane, making it very sensitive to low magnitude, short term climate fluctuations.Changes in lithology, molluscan species diversity, oxygen isotopes from gastropod shells, and sediment organic content permit division of the core into several intervals representing different environmental regimes. The basal sediments are older than 5130 RCYBP and resemble those of the Liberty Grove Member of the Pleistocene Horicon Formation. The oldest Holocene sediments recorded in the core are an organic rich layer dated at 5130 RCYBP, which accumulated in a depression on the surface of a sand bar. Continued rise in the local water table during the Nipissing Transgression produced paludal conditions in the area, which were followed by the onset of lacustrine conditions. During this interval, the area supported a diverse molluscan fauna. Minor, short term climate fluctuations are reflected in sediment and oxygen isotope changes which are absent from the record in deep water cores from Lake Michigan. This phase in the history of the area ended with the eutrophication of the pond and the development of dunes. Information from Whitefish Dunes pond and other onshore sites within the Lake Michigan basin are an important source of data for reconstructing the history of water levels and climate changes for this area of the Great Lakes drainage.

Paleolimnological significance of spinose and non-spinose morphs of Pyrgophorus hibbardi (Leonard and Franzen, 1944)

The basal portion of the Ogallala Formation (=‘Laverne Formation’) (Lower Pliocene) Beaver County, Oklahoma, contains an interesting assemblage of non-marine fossil molluscs that include both spinose and non-spinose forms of the aquatic gastropod species Pyrgophorus hibbardi. The origin and paleolimnological significance of the spinose morph has been a source of much conjecture that has influenced environmental reconstructions of this assemblage. In one hypothesis the spinose forms of P. hibbardi are assumed to be associated with brackish water conditions by analogy with some populations of a related hydrobiid Potamopyrgus jenkinsi. To test the hypothesis that the spinose forms lived under different water conditions than the non-spinose morphs, we analyzed 10 specimens each of the two varieties for stable oxygen and carbon isotope ratios in the shell aragonite.The mean isotope ratios for the smooth and spinose morphs show no significant difference (oxygen: t = 0.28, df = 18, P (T ≤ t) 0.78 n.s.; carbon: t = 0.96, df = 18, P (T ≤ t) 0.35 n.s). We conclude that the lack of a statistically significant difference between the means of the oxygen and carbon isotope values for the smooth and spinose morphs suggests that the two forms lived in waters having similar isotope signatures. The considerable range in oxygen isotope values recorded by both morphs of P. hibbardi, including values as high as 5–6‰, suggest that both morphs were associated with waters which were periodically evaporatively enriched in 18O.

Post-Chippewa oxygen isotope record from Cowles Bog, southern Lake Michigan basin

Previous studies of sediments and molluscs recovered from vibracores at Cowles Bog, a fen located in the Indiana Dunes National Lakeshore, along the south shore of Lake Michigan, reveal long and short term water level fluctuations during the last 6000 years. Low water events are indicated by zones of organic detritus, in which occasionally, iron oxide and calcium carbonate nodules, as well as selenite crystals have been precipitated. Oxygen isotope data from aragonitic shells of the gastropod Amnicola limosa (Say) collected from a sediment core provide a record of Middle to Late Holocene environmental changes for the fen. These data are in good agreement with previous interpretations of water level fluctuations based on changes in lithology and molluscan faunal abundance and composition. Below 366 cm the molluscan record is either absent or represented by shell fragments. The condition of shells in this interval suggests that the molluscs may have been exposed to subaerial weathering and reworking of older Holocene lake sediments, possibly during the low water Chippewa phase in the Lake Michigan basin (10000 YBP to 6000 YBP). Above 366 cm the core is characterized by a well preserved molluscan fauna. Relatively light isotopic values for the interval between 366 cm to 300 cm correlate with the transition from non-fossiliferous sands, peat and diamict to silty marl and calcareous sand, with a molluscan fauna dominated by taxa associated with permanent water bodies. The event producing these alterations, the Nipissing Transgression, marks a change from subaerial to ‘permanent’ lacustrine conditions that were not characterized by high net evaporation. Evidence for another series of environmental changes occurs between 284 cm and 198 cm. This evidence includes the: (1) appearance of aquatic molluscs at 280 cm that are associated with water bodies subject to significant seasonal water level changes; (2) intermittent accumulations of iron oxide nodules, calcium carbonate nodules, and organic layers interbedded with crudely horizontal layers of fine, calcareous, sand, suggesting periodic water level oscillations; (3) onset of major excursions in the oxygen isotopic values between 260 cm to 198 cm. Relatively high δ18O (PDB) values, possibly indicating evaporative enrichment of the water, correlate with a prominent shell debris layer at a depth of about 235 cm. Taken together, this evidence suggests that the core site was in the process of becoming isolated from Lake Michigan. This isolation occurred during a series of low water events during the later part of the Nipissing Transgression.