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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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North America
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Michigan Basin (1)
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United States
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Michigan
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Michigan Lower Peninsula
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Eaton County Michigan (1)
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commodities
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water resources (1)
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geologic age
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Paleozoic
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Carboniferous
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Mississippian
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Upper Mississippian
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Chesterian (1)
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Pennsylvanian
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Lower Pennsylvanian (1)
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Middle Pennsylvanian
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Atokan (1)
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Saginaw Formation (1)
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Primary terms
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ground water (1)
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North America
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Michigan Basin (1)
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Paleozoic
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Carboniferous
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Mississippian
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Upper Mississippian
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Chesterian (1)
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Pennsylvanian
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Lower Pennsylvanian (1)
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Middle Pennsylvanian
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Atokan (1)
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Saginaw Formation (1)
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sedimentary rocks
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clastic rocks
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mudstone (1)
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sandstone (1)
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shale (1)
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coal (1)
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sedimentary structures
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planar bedding structures
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bedding (1)
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stratigraphy (1)
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United States
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Michigan
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Michigan Lower Peninsula
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Eaton County Michigan (1)
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water resources (1)
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sedimentary rocks
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sedimentary rocks
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clastic rocks
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mudstone (1)
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sandstone (1)
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shale (1)
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coal (1)
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siliciclastics (1)
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sedimentary structures
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sedimentary structures
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planar bedding structures
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bedding (1)
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sediments
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siliciclastics (1)
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Late Mississippian (Chesterian) through early Pennsylvanian (Atokan) strata, Michigan Basin, USA
ABSTRACT The Carboniferous Michigan Basin is the subject of conflicting interpretations resulting from the lack of detailed stratigraphic analysis of relevant rock units. In this study, an ~610 m (2000 ft) section of recently acquired core material was evaluated on the basis of lithofacies and stacking patterns, stratigraphic contacts, and well-established regional geologic relations of Mississippian and Pennsylvanian strata. The Bayport formation is composed of seven distinct primary depositional lithofacies reflecting open-marine and shoal-water to restricted peritidal environments, typically capped by an exposure surface. Carbonate-dominated strata of the Bayport formation are interstratified but ultimately transition up section into siliciclastic-dominated strata (previously called the Parma Sandstone) deposited in tidally influenced, estuarine facies. Late Mississippian Bayport strata are sharply overlain by Pennsylvanian-aged siliciclastic lithofacies of the Saginaw Formation. These facies were deposited in a range of terrestrial and marginal-marine environments, from coarse-grained fluvial sandstones at the base (previously known as the Grand River Formation), to the finer-grained channel sandstones and floodplain mudstones of mixed fluvial and estuarine systems in the middle Saginaw Formation. Carbonaceous shales, mudstones, and thin coal intervals characterize the middle to upper Saginaw Formation. In the southern Michigan Basin, an important unconformity at the Mississippian-Pennsylvanian contact is represented by either an incised valley-fill succession or a prominent paleosol above the Bayport formation at the base of the Absaroka section in the Saginaw Formation. In upthrown areas adjacent to a major wrench fault, the Lucas fault in south-central Michigan, the Bayport formation is transitional upward from an intensely karsted limestone to a red-bed paleosol and then to primarily carbonaceous mudrock of the Saginaw Formation. In downthrown areas adjacent to the fault, the formation contact, and systemic unconformity, is a sandstone-on-sandstone contact. Climate-sensitive strata indicate a significant transition from predominantly arid conditions in the Mississippian Bayport formation to humid climate conditions in the Pennsylvanian Saginaw Formation across the Mississippian-Pennsylvanian systemic boundary. Previously, the Bayport formation was considered Meramecian in age; however, palynologic analyses of samples collected from core within the interval indicate a Chesterian (late Mississippian) age, representing a significant revision of existing Michigan Basin stratigraphy.
ABSTRACT This field trip is an excursion to exposures of Pennsylvanian bedrock at Grand Ledge, Michigan, as a backdrop for interdisciplinary examination of the sedimentologic, stratigraphic, and hydrologic research conducted on these important bedrock aquifer units. The areal extent of Pennsylvanian rocks in the central Lower Peninsula of Michigan is ~28,490 km 2 . Pleistocene glacial deposits overlie these units throughout the state, but the drift is thin and locally absent along the Grand River Valley, in and around Grand Ledge, Michigan. The geology of the Pennsylvanian deposits is known almost entirely from subsurface research, although sparse outcrops occur near Parma and Jackson in Jackson County and at Grand Ledge in Eaton County. These outcrops, especially the ones at Grand Ledge, constitute the only exposures of coal-bearing strata in Michigan where visitors can see massive sandstone, shale, coal, and associated strata, and fine-grained, chaotic, riverbank-slump facies. The sections of the field trip will attempt to relate Grand Ledge area deposits to the Pennsylvanian section at the state and regional scale. First, general geologic and stratigraphic relations will be described on the basis of knowledge from the nearby cities of Lansing and Mason, where diamond drill cores and geophysical logs from extensively studied groundwater contamination sites are available. Lithologic and geophysical logs from these sites will be reviewed under the pavilion. Next, lithologic type sections of the Pennsylvanian material in outcrop will be observed and discussed. An example of core from a nearby industrial site will be studied under the pavilion during lunch, and a final trip to outcrop will be made to discuss stratigraphic relationships in an effort to bring into perspective the complexities of Pennsylvanian strata in the Michigan Basin.