ABSTRACT This thesis embraces and expands upon a century of research into disparate geological enigmas, offering a unifying catastrophic explanation for events occurring during the enigmatic mid-Pleistocene transition. Billions of tons of “Australasian tektites” were dispatched as distal ejecta from a target mass of continental sediments during a cosmic impact occurring ca. 788 ka. The accepted signatures of a hypervelocity impact encompass an excavated astrobleme and attendant proximal, medial, and distal ejecta distributions. Enigmatically, the distal tektites remain the only accepted evidence of this impact’s reality. A protracted 50 yr search fixated on impact sites in Southeast Asia—the location of the tektites—has failed to identify the requisite additional impact signatures. We postulate the missing astrobleme and proximal/medial ejecta signatures are instead located antipodal to Southeast Asia. A review of the gradualistic theories for the genesis and age of the “Carolina bay” landforms of North America finds those models incapable of addressing all the facts we observe. Research into 57,000 of those oriented basins informs our speculation that they represent cavitation-derived ovoid basins within energetically delivered geophysical mass surge flows emanating from a cosmic impact. Those flows are seen as repaving regions of North America under blankets of hydrated impact regolith. Our precisely measured Carolina bay orientations indicate an impact site within the Laurentide ice sheet. There, we invoke a grazing regime impact into hydrated early Mesozoic to late Paleozoic continental sediments, similar in composition to the expected Australasian tektites’ parent target. We observe that continental ice shielded the target at ca. 788 ka, a scenario understood to produce anomalous astroblemes. The ensuing excavation allowed the Saginaw glacial lobe’s distinctive and unique passage through the Marshall Sandstone cuesta, which encircles and elsewhere protects the central region of the intracratonic Michigan Basin. Subsequent erosion by multiple ice-age transgressions has obfuscated impact evidence, forming Michigan’s “Thumb” as an enduring event signature. Comprehensive suborbital modeling supports the distribution of distal ejecta to the Australasian tektite strewn field from Michigan’s Lower Peninsula. The mid-Pleistocene transition impact hypothesis unifies the Carolina bays with those tektites as products of an impact into the Saginaw Bay area of Lake Huron, USA. The hypothesis will be falsified if cosmogenic nuclide burial dating of Carolina bay subjacent stratigraphic contacts disallows a coeval regolith emplacement ca. 788 ka across North America. We offer observations, interdisciplinary insights, and informed speculations fitting for an embryonic concept involving a planetary-scale extraterrestrial impact.

ABSTRACT This field guide discusses the dune types and processes, ecology, and geomorphic history of the largest freshwater dune systems on the southeastern shore of Lake Michigan. From north to south, stops include P.J. Hoffmaster State Park, Gilligan Lake/Green Mountain Beach Dune, Saugatuck Harbor Natural Area, and Grand Mere and Warren Dunes State Parks, Michigan. All of the sites are low, perched transgressive dune complexes. Moving from the lake inland, the typical dune complex in this area consists of incipient foredunes, an established foredune ridge, a parabolic dune complex, and a back-dune ridge complex. All stages of ecological succession are typically present in the larger dune complexes. Surface changes in Lake Michigan dunes are driven by spatial gradients in sand flux, which, in turn, are determined by a complex interaction among wind dynamics, vegetation patterns, and preexisting topography. Surface change patterns are modified by seasonal effects, with the majority of sand transport being associated with strong storms in the autumn, winter, and early spring. Sand can be temporarily stored in niveolian deposits during the winter, leading to oversteepened slopes, which collapse during the spring thaw. Current dune complexes largely formed during and after the rise in lake levels to the Nipissing high lake level, ca. 4.5 ka. Broad fields of relatively low dunes developed during the lake-level drop following the Nipissing high. Beginning with the rise to the Algoma high lake level, ca. 3.2 ka, the lakeward edges of these fields were episodically reworked, forming large parabolic dune complexes. A period of widespread dune stability formed the Holland Paleosol, a spodic inceptisol. Dune growth and migration resumed prior to European settlement of the area and continues today. Foredune complexes grow wider and higher during periods of low lake levels, but narrow during periods of high lake level due to scarping at their lakeward edges.

ABSTRACT Pennsylvanian red beds are the youngest known rocks in the Michigan Basin. Two new formation-level units, the Pewamo Formation and the Haybridge strata, have recently been described. The Pewamo Formation, composed of Pennsylvanian red sandstones and minor laminated mudstones, is known from outcrops, abandoned quarries, and one core in Ionia County. The Haybridge unit is located in the shallow subsurface and in coal mine tailing piles in Shiawassee County. It consists of red sandstone, red mudstone, coal, and gray mudstone, all hosting Pennsylvanian macroscopic plant fossils. Neither the Pewamo nor the Haybridge rocks have any demonstrated relationship to red core cuttings reported as Jurassic from the central Lower Peninsula of Michigan. No firm evidence exists for Jurassic, or any other post-Pennsylvanian rocks in the Michigan Basin. The red core cuttings may be glacial sediments with reworked palynomorphs from rocks transported from elsewhere. A shallow coring project, followed by detailed sedimentologic, petrographic, mineralogic, and paleontologic studies, is necessary to: (1) refine the vertical and lateral stratigraphy of the Pennsylvanian rocks in Michigan; (2) solve the “Jurassic red bed problem”; and (3) understand the late Pennsylvanian–Pleistocene history of the Michigan Basin.

ABSTRACT The objective of this study was to investigate the geological controls on stratigraphic and lithologic variability in the Ordovician Utica Shale and related Collingwood Member in the Michigan Basin in order to assess CO 2 sequestration cap rock (seal) potential, including petrophysical properties and mechanical fracture responses. Twelve conventional cores and hundreds of modern well logs from the Michigan Basin were analyzed to correlate and calibrate wireline log signatures with whole-rock mineral composition (from X-ray diffraction analysis) and mechanical properties (from core analysis) to identify brittle, fracture-prone zones, and to validate the Utica Shale as a regional geologic seal. Analysis using scanning electron microscopy with Quantitative Evaluation of Minerals by Scanning Electron Microscope (QEMSCAN ® ) software was employed to image pores and for quantitative analysis of mineralogy, texture, and porosity. Mercury injection capillary pressure and triaxial strength testing was conducted to assess petrophysical properties and mechanical responses. The results suggest the Utica Shale could reliably contain upwards of 1500 m of buoyant, supercritical CO 2 stored in underlying Cambrian and Ordovician reservoirs.

ABSTRACT Despite extensive research on Silurian (Niagaran–Wenlockian) reefs, most studies concerning faunal abundance and distribution have been qualitative studies with an emphasis on taxonomy, paleoecology, and evolution. This study is the first quantitative study of relative abundance and distribution of fauna throughout a single Wenlockian reef located in the southern trend of the Michigan Basin. Building on an established sequence stratigraphic framework with wind directions surmised from known paleogeographic location, the purpose of this study was threefold: (1) to quantitatively determine the relative abundances of fauna from subsurface cores of Ray Reef and show how they are tied to the established sequence stratigraphic framework; (2) to determine if the probable wind and current directions, along with water depth, influenced the morphology and distribution of fauna on the reef; and (3) to analyze the influence of wind and current on syndepositional marine cementation. Relative faunal abundance differed among the leeward, windward, and reef crest locations. Overall faunal density was highest in the crest and lowest along the leeward side of the reef complex. Diversity was highest in the crestal portion of the reef complex and in the reef core facies, in general. Changes in faunal morphology and community replacement were seen repeatedly through all cores in association with shallowing-upward conditions, which coincided with third-order stratigraphic and higher-frequency sequence stratigraphic cyclicity. The percentage of syndepositional marine cement was highest on the windward side and lowest on the leeward side. As has been reported in other reef complexes of varying geological ages, results of this study indicate that the core of the Silurian reef was composed mostly of rubble or debris, relative to the smaller proportion of in situ fauna.

ABSTRACT Middle Devonian Dundee Formation carbonates are prolific hydrocarbon reservoirs throughout the Michigan Basin that have produced in excess of 375 million barrels of oil from more than 100 fields. There is limited fundamental understanding of the complex facies mosaics and stratigraphic architecture in this interval. This stratigraphic complexity is likely controlling the reservoir architecture in both lateral and vertical dimensions. The primary goal of this study was to develop a more detailed understanding of the stratigraphic architecture of the Dundee Formation in the South Buckeye field through utilization of closely spaced subsurface cores and accompanying wireline logs. Data on facies types, vertical stacking patterns, and variability within the field were then combined with modern and ancient analogs to develop the parameters to populate a series of three-dimensional (3-D) static geostatistical models. A fundamental question was to determine if the geographic distribution of patch reefs in the South Buckeye field could be accurately modeled with industry-standard geostatistical software (Schlumberger’s Petrel) based on core and wireline log data without a tie to 3-D seismic data. This study used geometrical data from multiple modern and ancient depositional analogs to constrain the geostatistical models. The geographic distribution and internal architecture of patch reefs were defined through the integration of petrophysical and high-density petrographic analyses from the subsurface core data. Based on core, wireline log analysis, and depositional analogs, three end-member interpretations were modeled geostatistically and used to define the distribution and scale of the patch reef reservoirs in the South Buckeye field. As with many carbonate reservoirs, a 3-D static reservoir model is a critical step in the workflow for efficient hydrocarbon extraction, natural gas storage, and CO 2 sequestration, and this study provides insight into the Michigan Basin Dundee Formation patch reefs as well as possibly other Devonian carbonates and reef trends around the world.

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 The Middle Ordovician St. Peter Sandstone in the Michigan Basin is a target for hydrocarbon exploration/production, and carbon sequestration and geologic storage. The St. Peter Sandstone is predominantly a marine sandstone with four dominant lithologic facies. The uppermost facies contains zones of porosity and good reservoir quality. Because of the mostly uniform, quartzose detrital grain composition, diagenesis played a dominant role in reservoir quality development. The distribution of diagenetic alteration is believed to result from variations in depositional setting and related geologic processes, including variations in sediment accumulation rate. Early marine carbonate cements preserved precompaction intergranular space available for late diagenetic processes, including the inhibition of quartz overgrowth and decementation. Data from conventional cores, petrographic/petrologic techniques, and wireline logs were used to assess stratigraphic and sedimentologic controls on vertical and horizontal variability of reservoir quality. Evidence for early marine cements and related enhanced reservoir quality is associated with thin shale beds (interpreted as flooding surfaces), which are regionally correlative across the basin.

Accurately reconstructing the rate of movement and extent of eolian dunes over thousands of years is a challenging endeavor. In this paper, we refine the methodology for utilizing lakes and bogs downwind of dune fields as precise recorders of past eolian activity. Sediment cores from two Allegan County lakes and one bog associated with dunes were studied to evaluate the importance of the various sand transport pathways into lakes and bogs. Goshorn Lake's western edge directly abuts a large parabolic dune. Sand concentrations decrease in cores away from the dunes, possibly reflecting avalanching into the lake followed by sediment gravity flows along the lake bottom. Sand input from stream flow was minor. The Allegan Bog core records a fen-emergent bog transition coincident with a decrease in the sand influx. Poorly understood shoreline processes may have contributed sand to the basin's center before the bog's emergence. Sand in Gilligan Lake cores is texturally similar to adjacent dune sand and the eolian activity history derived from this sand is nearly identical to the history derived from the dune's paleosols and optically stimulated luminescence ages. A proposed lake and bog sampling strategy includes choosing sites in the lee of large dunes edged with emergent vegetation and away from steep slopes or stream inlets. The lake's bathymetry should also be considered. Distinguishing between grain fall sedimentary structures and mass movement or sediment gravity flows is important. This strategy provides relatively high resolution, continuous eolian activity histories that can be correlated with paleoenvironmental proxies from the same cores.