“…the frustration of discovering an unusually good exposure or feature only to have it quarried or covered in succeeding weeks is disheartening. On the other hand, quarry advance enables one to project the geology from time to time, which helps one to fill in the three-dimensional puzzle.” — Gutschick (1972) ABSTRACT We summarize and then build on the three decades of geological mapping and analyses done by Ray Gutschick at the Newton County (Kentland) quarry. We present our own new data and ideas on the kinematics and significance of radial faults, shock metamorphism, petrography and diagenesis of impact breccia dikes, impactite geochemistry, and a preliminary new paleomagnetically determined Jurassic age for the crater. We list and describe the stops for this field excursion.

ABSTRACT This field guide summarizes the main known and unknown aspects of the impact geology of the Kentland impact structure, and includes sections on results from recent research, evidence of impact, age of impact, and shock metamorphism. It is intended to lead visitors through the spectacular, three-dimensional outcrops in the central uplift of the structure, exposed in the Newton County Stone (Kentland) Quarry, western Indiana.

Abstarct The Kentland Dome is an enigmatic, thought-provoking, structurally complex anomaly, subsequently covered by glacial drift, in an area surrounded by normal, undisturbed, flay-lying Paleozoic strata. Rocks in thecore of the Kentland structure havebeen uplifted more than 2,000 ft (610 m), folded into a structural dome, and intricately disrupted by faulting. A significant portion of the Ordovician central core is revealed in the spectacular Kentland Quarry. One must see the quarry and its superb rock exposures that challenge the imagination to grasp the magnitude of the anomaly and complexities of its structural pattern. The oldest quarries at Kentland (McKee and Means) date from more than 100 years ago. Since that time, generations of geologists, applying the scientific method to the exposures in the continually expanding quarry, have built a case history on the evolution of thought to the origin of this unusual structure. The problem has been, and remains, to explain this geometic jigsaw puzzle with respect to its spatial pattern, chronology of disruption, and genesis of deformational mechanics. For example, shatter cones and their orientations in the Kentland Quarry inspired Dietz (1947, 1972) to suggest a meteorite-impact origin simply because the cone apices point upward upon reconstruction of the strata to their normal, flat-lying position. Are Dietz, and other devotees of extraterrestrial origin, correct? Or are there plausible alternative endogenetic explanations? References to significant developments of the quarries at Kentland and in thought on the origin of the structure can be found in various annual reports

Abstract This guidebook volume is a compilation of field excursions offered at the 47th annual meeting of the North-Central Section of the Geological Society of America, held in Kalamazoo, Michigan, May 2013. These field trips examine a wide range of geological time intervals and topics, from Silurian salt, to Cretaceous cosmic impact, to newly interpreted Mississippian–Pennsylvanian Michigan stratigraphy, to Quaternary glacial landscape formation, sand dune development, and present-day coastal bluff stability/erosion issues. Trips geographically range throughout southern Michigan and northern Indiana from Detroit, Michigan, in the east to the Kentland Quarry in Indiana to the west. Early depositional events within the Michigan Basin are examined deep underground in the Detroit Salt Mine (trip leaders: W.B. Harrison III and E.Z. Manos [onsite leader]). This salt mine has been in operation for more than 100 years, and extends for miles beneath the city of Detroit. Kentland Quarry, located in northwest Indiana, is the site of a Cretaceous-aged meteorite impact (trip leader: J.C. Weber). This site allows for surface examination of a similar style impact event that occurred in now buried Ordovician-age (Trenton) rocks located in Cass County, (southwest) Michigan. Mississippian-aged fluvial deposits have been traditionally classified as the youngest bedrock exposed in Michigan. These rocks crop out in the center of the Michigan Basin near Grand Ledge, Michigan (trip leaders: N.B.H. Venable, D.A. Barnes, D.B. Westjohn, and P.J. Voice). Younger, more recently identified, Pennsylvanian rocks will be the subject of a related core workshop at the Michigan Geological Repository for Research and Education (MGRRE) in Kalamazoo (workshop leaders: S. Towne, W.B. Harrison, and D.B. Westjohn). The regional, surficial geology of southwest Michigan is highlighted by three field trips. The first trip details the glacial landforms and sedimentary features formed by the differing dynamics of the Michigan and Saginaw lobes of the Laurentide Ice Sheet (trip leaders: A.E. Kehew, A.L. Kozlowski, B.C. Bird, and J.M. Esch). The two other trips follow along the Lake Michigan eastern shoreline and examine development of sand dune complexes (trip leader: E. Hansen) and present-day, coastal bluff stability and erosion issues (trip leaders: R.B. Chase and J.P. Selegean).

ABSTRACT The extremely important role of groundwater has been largely overlooked in studies of meteorite and comet impact processes. Beyond the radius of plasma generation, impacts can produce massive shattering in saturated porous rocks. Fluid pressure rise reduces rock strength and facilitates hydrofracture, to produce intraformational monomict breccias, faulting, and generation of mobile polymict breccia slurries. Decompression of a deep “transient” crater accounts for complex central uplift and gravitational collapse of tremendous slide blocks that in turn cause injection and ejection of fluidized breccia. As pore fluid pressures equilibrate, frictional strength increases, and the structural form is locked into stability. Evidence is reported here for Kentland, Indiana, where quarry rocks display relatively low pressure-temperature (elastic to ductile transition, 100 kb–100 °C) impact phases of the model of D. Stöffler. Breccias include monomict, polymict, mixed polymict-fault, and conventional fault types. The monomict breccias are associated with aquifer beds and formed by pervasive shockwave transmission on impact. Polymict breccias are derived from all rock types and formed from late stage injection-ejection pseudoviscous slurries. These processes can apply to similar impacts like Wells Creek, Flynn Creek, Decaturville, Sierra Madre, and many others.

The Weaubleau structure consists of a 19-km circular feature that contains deformed Mississippian limestones. The age of the structure is stratigraphically constrained between deposition of the deformed Osagean limestones and the overlying undeformed Pennsylvanian (Desmoinesian) units. Paleomagnetic samples were collected from tilted Burlington-Keokuk Limestone (undivided), a polymict breccia inside the structure, and undeformed Burlington-Keokuk Limestone outside of the structure. Stepwise thermal and alternating-field demagnetization of tilted limestone samples reveals a characteristic remanent magnetization (ChRM) with southeasterly declinations and shallow positive inclinations with maximum unblocking temperatures of 475 °C. The ChRM is post-tilting and resides in magnetite. The pole is 30.2°N, 135.4°E (d p = 4.1°, d m = 7.9°), which lies on the Late Mississippian portion of the apparent polar wander path. The breccia samples only contain a present-day field component. Many of the samples from outside the structure contain a present-day field component residing in magnetite, although some contain a poorly defined component with southeasterly declinations and moderate positive inclinations. The ChRM is apparently localized within the deformation feature. Since the ChRM is post-tilting, the age of the deformation has been constrained better than the stratigraphic age. The post-deformational ChRM is not a shock magnetization and is interpreted as a chemical remanent magnetization (CRM). One hypothesis for the origin of the CRM is hydrothermal fluids that were activated as a result of the impact. This hypothesis is consistent with 87 Sr/ 86 Sr values in the deformed limestones, which suggest alteration by radiogenic fluids.

ABSTRACT The historic town of New Harmony is located along the Wabash River in Posey County, Indiana, and served as a focal point for natural scientists, especially geologists, in the early nineteenth century. Notable geologists that lived and worked in New Harmony during this time include Edward Travers Cox, William Maclure, Fielding Bradford Meek, Joseph Granville Norwood, David Dale Owen, Richard Dale Owen, Benjamin Franklin Shumard, Gerard Troost, and Amos Henry Worthen. Other natural scientists who worked in New Harmony include Charles Alexandre Lesueur and Thomas Say, and the town was also visited by James Hall, Leo Lesquereux, Sir Charles Lyell, and Alexander Philipp Maximilian, Prince of Wied. The purpose of this field-trip guide is to highlight the scientific and geologic enterprise that operated in nineteenth-century New Harmony, Indiana. There will be a tour of historic buildings including laboratories used by David Dale Owen, such as the Rapp-Owen Granary and his fourth laboratory, which was constructed in 1859. Furthermore, field-trip participants will visit a new geology exhibit at the Working Men’s Institute, an organization established by William Maclure in 1838. The field excursion will also visit historically significant localities, including Mississippian and Pennsylvanian exposures, the type section of the West Franklin Limestone, and a Pennsylvanian paleobotanical site that yielded extensive collections of plant fossils in the mid-nineteenth century. Finally, this field trip will provide an opportunity to discuss the importance of art to geological studies in the early nineteenth century. Specifically, hand-colored geologic maps, cross sections, and renderings of fossils were included with many of the scientific reports of historic New Harmony, and are reflected by the superb artwork of Charles Alexandre Lesueur, David Dale Owen, and Thomas Say. Access to view their original scientific artwork is possible only through special arrangement with the Working Men’s Institute.

Abstract Geology has been part of the curriculum at Wheaton College, Illinois, since it was established in 1860 as a non-denominational, Christian liberal arts college. The school continues to maintain a strong identity with evangelical Christian theology and subculture. The first president Jonathan Blanchard recruited George Frederick Barker to teach geology and natural history on the personal recommendations of the renowned geologists Agassiz, Silliman and Hitchcock. Barker taught at Wheaton for only one year, and was followed by a succession of other young scientists who kept geology in the curriculum to the end of the nineteenth century. These teachers respected the geological evidence for an ancient Earth and interpreted the creation days in Genesis 1 as representing extended epochs of God's creative activity. In the early twentieth century, Professors James Bole and L. Allen Higley harmonized mainstream geological history and the Bible through the gap or ruin–restoration interpretation, wherein eons of geological time preceded six days of Edenic re-creation only thousands of years ago. Higley's background in geology, his role in recruiting additional science faculty staff, and his influence among fundamentalists set the stage for the acceptance by subsequent Wheaton geologists of mainstream geology and their rejection of emerging popular fundamentalist ideas about a six day creation and Flood geology. Geology was established as a major subject in 1935 and an independent Geology Department was established in 1958. Geology education at Wheaton College was profoundly influenced by the tension over creation issues in the evangelical subculture, and different models for understanding the relationship between science and Christian theology have been employed by teachers and students.

ABSTRACT We reconstructed a record of the micrometeorite flux in the Late Cretaceous using the distribution of extraterrestrial spinel grains across an ~2 m.y. interval of elevated 3 He in the Turonian Stage (ca. 92–90 Ma). From ~30 m of the limestone succession in the Bottaccione section, Italy, a total of 979 kg of rock from levels below and within the 3 He excursion yielded 603 spinel grains (32–355 μm size). Of those, 115 represent equilibrated ordinary chondritic chromite (EC). Within the 3 He excursion, there is no change in the number of EC grains per kilogram of sediment, but H-chondritic grains dominate over L and LL grains (70%, 27%, and 3%), contrary to the interval before the excursion, where the relation between the three groups (50%, 44%, and 6%) is similar to today and to the Early Cretaceous. Intriguingly, within the 3 He anomaly, there is also a factor-of-five increase of vanadium-rich chrome spinels likely originating from achondritic and unequilibrated ordinary chondritic meteorites. The 3 He anomaly has an unusually spiky and temporal progression not readily explained by present models for delivery of extraterrestrial dust to Earth. Previous suggestions of a relation to a comet or asteroid shower possibly associated with dust-producing lunar impacts are not supported by our data. Instead, the spinel data preliminary indicate a more general disturbance of the asteroid belt, where different parent bodies or source regions of micrometeorites were affected at the same time. More spinel grains need to be recovered and more oxygen isotopic analyses of grains are required to resolve the origin of the 3 He anomaly.