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Sangamonian
Significance of Pleistocene fluvial systems and glaciations on the landscape evolution of northern Kentucky
ABSTRACT Pleistocene glacial and interglacial episodes had a profound influence on erosion, sediment transport, and topographic expression in the Midwestern United States. Northern Kentucky hosts a variety of fluvial and glacial features that record these Quaternary advances and retreats of the Laurentide ice sheet. This field trip highlights the major glacial and interglacial episodes of the Pleistocene, including the Pliocene–Early Pleistocene Teays drainage system, the Early–Middle Pleistocene pre–Illinois glacial Episode, the Middle Pleistocene Yarmouth interglacial, the Illinois glacial Episode in the Middle Pleistocene, the Sangamon interglacial, and the Late Pleistocene Wisconsin Episode. The Old Kentucky River was tributary to the Teays, depositing sands at ca. 1.5 Ma, confirmed by multiple 10 Be- 26 Al cosmogenic radionuclide burial ages. Glacial till uncoformably overlies Old Kentucky River sands and demonstrates that pre-Illinois ice extended into Kentucky. The modern-day course of the Ohio River was incised after the pre−Illinois Episode, and then aggraded with transportation of Illinois Episode glacial outwash. Deposition of outwash at the mouths of tributaries caused impoundment and slackwater deposition in tributary valleys; the Claryville Clay has long been assumed to represent a pre-Illinois lacustrine deposit, but new optically stimulated luminescence feldspar geochronology yields a Middle Pleistocene age of ca. 320 ka. We have not observed Illinoian till in Kentucky. The final advance of the Laurentide ice sheet did not reach Kentucky, however, high sediment volumes were transported along the Ohio River and impounded tributaries, similar to the Illinois Episode.
GROUND-PENETRATING-RADAR CHARACTERIZATION AND POROSITY EVOLUTION OF AN UPPER PLEISTOCENE OOLITE-CAPPED DEPOSITIONAL CYCLE, RED BAYS, NORTHWEST ANDROS ISLAND, GREAT BAHAMA BANK
Controls On Lower-Coastal-Plain Valley Morphology and Fill Architecture
Age, genesis, and paleoclimatic interpretation of the Sangamon/Loveland complex in the Lower Mississippi Valley, U.S.A.
Corroboration of Sangamonian age of artifacts from the Valsequillo region, Puebla, Mexico by means of diatom biostratigraphy
Stability of Late Pleistocene Reef Mollusks from San Salvador Island, Bahamas
Paléophytogéographie de la formation de Scarborough: nouvelles données et implications
Rapid sea-level changes at the close of the last interglacial (substage 5e) recorded in Bahamian island geology: Comment and Reply
Sequence Stratigraphy and Composition of Late Quaternary Shelf-Margin Deltas, Northern Gulf of Mexico
Séquence de la transition Illinoien–Sangamonien : forage IAC-91 de l'île aux Coudres, estuaire moyen du Saint-Laurent, Québec
Palynologie et paléoenvironnements des épisodes du Sable de Lotbinière et des Varves de Deschaillons (Pléistocène supérieur) de la vallée du Saint-Laurent
Thermoluminescence chronology of Toronto-area Quaternary sediments and implications for the extent of the midcontinent ice sheet(s)
The Hillsborough, New Brunswick, mastodon and comments on other Pleistocene mastodon fossils from Nova Scotia
A paleoenvironmental study of the molluscs from the Don Formation (Sangamonian?) Don Valley Brickyard, Toronto, Ontario
Sediments, soils, and fossils are used to interpret paleoenvironmental conditions during the last interglacial-glacial transition in Illinois. The sediments include the classic Sangamonian-Wisconsinan and Wisconsinan/Farmdalian-Woodfordian successions; both consist of loess overlying pedogenically modified or generally colluviated sediment. Although the contacts between the loess and soil are defined as isochronous, they are diachronous. The age of basal Wisconsinan deposits spans from at least 50 to 22 ka, and the age of basal Woodfordian sediments spans from 25 to 20 ka. Recognition of the last interglacial episode, the Sangamonian Age, is based on Mollisols, Alfisols, and Ultisols that formed in Illinoian glacigenic deposits. Sangamonian flora and fauna, although sparsely preserved, include pollen well represented by deciduous trees, grasses, and Ambrosia. Sangamonian vertebrates included giant tortoise, mastodon, giant beaver, snapping turtle, and short-nosed gar. The Wisconsinan Age (Altonian Subage) began as Roxana Silt (loess) was deposited under periglacial conditions. The vegetation was characterized by coniferous trees that grew in weakly developed, often organic-rich, cryoturbated soils. Periglacial conditions persisted during the Altonian and Farmdalian Subages, from before 50 ka to about 25 ka, after which loess, outwash, and till were deposited under glacial conditions during the Woodfordian Subage and much of the remainder of the Wisconsinan Age. The vegetation that grew during the last glacial episode includes plants that are now found at and north of the treeline in Canada.
Early Wisconsinan in the north-central part of the Lake Erie basin: A new interpretation
The Bradtville drift, the Canning till, and their correlatives in southwestern Ontario have been previously thought to be early Wisconsinan in age. Here another alternative is offered, whereby the Bradtville drift is assigned to the Illinoian stage, the lowermost Member A of the overlying Tyrconnell Formation to the late Sangamonian; Eowisconsinan, or the earliest part of early Wisconsinan, and its Member B to the early Wisconsinan substage. The age of the Canning till is still unknown. Member A of the Tyrconnell Formation is an accretion gley that formed about 20 m below the present level of Lake Erie, thus requiring a low outlet for the Erie basin. At that time, the Erie basin was drained probably by the buried Erigan channel, which extends about 50 m below the present level of Lake Erie. Member B of the Tyrconnell Formation is varved glaciolacustrine silt and clay, the deposition of which required a rise of lake level above the present one. This rise could have been caused by the Ontario lobe overriding the Niagara peninsula, possibly as far as Gowanda, New York; however, the ice margin remained in the eastern part of Lake Erie. The above hypothesis is supported by available lithologic and paleoecologic data from the region adjoining the north-central and eastern part of Lake Erie, but supporting numerical age determinations beyond the range of radiocarbon dating are still lacking.
The sedimentary and biological record of the last interglacial-glacial transition at Toronto, Canada
A substantial Sangamon interglacial (isotope stage 5) and subsequent Wisconsin glacial sedimentary record is preserved at Toronto, Canada. The age of individual stratigraphic units is poorly constrained, however. An interglacial sequence records climatic deterioration from warm temperate to subarctic. The interglacial Don Beds, resting on a presumed Illinoian till, were deposited on a storm-influenced shoreface of an ancestral Lake Ontario in water depths that increased over the recorded time interval from about 2 to 20 m. Pollen and faunal analyses identify a climatic deterioration in the upper Don from warm-temperate conditions, with mean annual temperatures some 2 °C warmer than at present, to cool temperate, with temperatures lowered by about 3 °C. Continued cooling is recorded in overlying deeper-water deltaic sediments of the Scarborough Formation, but later climatic amelioration and the return of mixed forest are suggested by the pollen record and by caddisfly fauna. The youngest deltaic sediments, lying immediately below a Wisconsin glacial complex, were deposited in a subarctic setting in an ice-dammed lake, with local mean annual temperatures depressed by at least 7 °C. This chapter identifies the likely continuity of the Don Beds and Scarborough Formation and places them in an expanded “Sangamon” interglacial possibly equivalent to the whole of stage 5 (i.e., 130–75 ka). The biological record at Toronto for this stage indicates one or more phases of cooling when continental-glacier ice may have developed in North America; this record can be favorably compared with the marine oxygen-isotope record with its evidence of increased global ice volumes during stage 5. The subsequent Wisconsin record at Toronto is not well constrained by radiometric age dating but indicates that maximum regional expansion of the Laurentide Ice Sheet in the eastern Great Lakes area occurred after 25 ka.
Sangamonian and early Wisconsinan events in the St. Lawrence Lowland and Appalachians of southern Quebec, Canada
In the St. Lawrence Lowland of southern Quebec, an early Wisconsinan glacial advance deposited the Levrard Till. This glacial event, known as the Nicolet Stade, is tentatively correlated with marine oxygen-isotope stage 4. Radiocarbon and thermoluminescence ages bracket the Nicolet Stade between 90 and 70 ka. This advance was preceded and followed by periods of free drainage during which were deposited the Lotbiniere Sand and St. Pierre Sediments, two nonglacial units dated at or beyond the limit of the radiocarbon method. Available evidence suggests that the Deschaillons Varves were deposited ca. 80 ka in a large glacial lake that was impounded in front of the Laurentide Ice Sheet as it advanced up the St. Lawrence Valley. In the Appalachian Uplands, fluvial and lacustrine sediments of the Massawippi Formation were probably deposited at the end of the Sangamonian Interglacial. These sediments underlie the Chaudiere Till, a unit in which the occurrence of distinctive lithological indicators is taken as evidence that a regional episode of westward to southwestward ice flow prevailed at the onset of the last glaciation. The proposed paleogeographic reconstruction suggests that the development of an independent ice cap in the northeastern Appalachians played a key role during the early part of the Wisconsinan Glaciation in southern Quebec. This independent ice mass flowed southwestward across the Appalachian Uplands of southern Quebec and eventually coalesced with the Laurentide Ice Sheet, which was advancing up the St. Lawrence Valley.
The dating of events older than 50 ka, the limit of the radiocarbon method, has been a major drawback in assessing the chronology of the Quaternary. Several new methods have been applied to the dating of pre-late Wisconsinan organic beds in Nova Scotia. These methods include U/Th disequilibrium dating of wood and shells, amino-acid racemization dating of shells, and wood and electron spin resonance dating of shells. These methods are not without problems, and must be assessed together, and in concert with geologic evidence, in establishing a chronology. Evidence of the penultimate interglacial (marine isotopic stage 7) has been found in southern Nova Scotia. A raised marine platform, forest beds beneath till, and glacially-resedimented marine deposits were all formed during the last interglacial or Sangamonian stage (stage 5). Middle Wisconsinan U/Th and radiocarbon dates are questionable, so the chronology of post-Sangamonian events is not well constrained. Post-Sangamonian erosional and depositional stratigraphy indicates that at least four phases of ice flow have affected the Nova Scotia region. The earliest of these flows was a major advance that crossed the Gulf of St. Lawrence and Bay of Fundy (ice-flow phase 1). Later, separate ice caps and divides formed in areas adjacent to the province and the province itself (ice-flow phases 2–4). There is evidence for ice retreat between phases 1 and 2 in offshore areas and locally on land. Nova Scotia was probably covered with ice throughout the Wisconsinan stage (marine isotopic stages 4 to 2).
The Sangamonian and early Wisconsinan glacial record in the western Canadian Arctic
Widespread till sheets, glacial lake and glacial-marine sediments on Banks, Victoria, and Melville islands, and on the Beaufort Sea Coastal Plain of the Canadian mainland, may record a late Pleistocene glacial advance which extended to the area as early as the Sangamonian (broad sense) to early Wisconsinan. These sediments overlie beds of interglacial character and underlie in places nonglacial deposits, which have provided both nonfinite and finite ages, and glacial sediments of unquestionable late Wisconsinan age. In other places only a single till sheet is observed between the last interglacial and Holocene sediment suites. Although some workers have argued that the glacial units mentioned above are all late Wisconsinan, stratigraphic, paleoecologic, and chronologic data ( 14 C, Th/U, and amino acid analyses), from several localities, indicate that the glacial sediments are of likely Sangamonian (broad sense) to early Wisconsinan age and that the nonglacial beds underlying or overlying these date respectively from the Sangamonian and middle Wisconsinan. The dispersal centre during the ice advance was situated, as during other advances in northwestern Canada, west of Hudson Bay. The ice generally extended further during the Sangamonian (broad sense)/early Wisconsinan than the late Wisconsinan but not as far as it did during the early and middle Pleistocene. To help resolve apparent incongruities in interpretation of the late Pleistocene deposits and ice limits it is postulated that extensive Keewatin Sector Ice of the Laurentide Ice Sheet may have first advanced in northwestern Canada during the Sangamonian (broad sense)/early Wisconsinan and remained there until it finally disappeared in the late Wisconsinan.