Field & Topical Conferences
SVP First North American Summer Field Conference
Hanna and Carbon Basins, South-central Wyoming
Cosponsored by The University of Wyoming, Department of Geology and Geophysics
August 5-7, 2008
General theme — "The Importance of Field-based Geological Documentation to Paleobiological Research"
Co-organizers: Jay Lillegraven, Jaelyn Eberle, Pennilyn Higgins, and Mark Clementz
Applications for the Field Conference are due April 30, 2008.
Principal Scientific Goals for the Conference:
This conference centers on special opportunities, as gained uniquely through the field study of rocks, to the discipline of paleobiology. The trip will be practical, emphasizing on-site examination of documented examples involving fossil vertebrates in detailed geological context. How did regional tectonism (expressed through changing sedimentary sources, appearance of well-defined basins, development of various nonconformities, and influences of superficial versus deep-centered faulting) affect our stratigraphic interpretations? In turn, how did post-depositional modification of physical stratigraphy affect our interpretations of organic evolution and biogeographic change through geologic time? How did basin evolution influence ancient geochemical environments, and how did that complex interaction affect the bias, or even the very existence, of a fossil record? In what new ways can stratigraphic sampling for isotopic geochemistry be used in concert with traditional biostratigraphy to help accept or reject claims of temporal correlation within and among basins? Looking broadly, how reliable are existing stratigraphic studies upon which so much of our interpretation of North American vertebrate evolution depends? Is field-based research still necessary in the 21st century, or has enough already been done on this continent and elsewhere? Do theoretically oriented specialists in paleobiology really need sophisticated knowledge about the strengths and limitations of procedures in field geology?
General Background:
The field conference will involve three day-trips (conducted from the town of Medicine Bow) to parts of the Hanna and Carbon Basins. These relatively tiny, Laramide basins in south-central parts of Wyoming have long been recognized for their astonishingly thick sections of marine and nonmarine, Upper Cretaceous and Paleocene strata. Originally, the Hanna and Carbon Basins were interpreted as discrete centers of deposition that had separate geological histories. We now recognize, however, that they represent eastern depositional components of an originally unified, enormous Green River Basin that secondarily became subdivided during the Eocene by deep-centered, basement-involved faulting. Because of regional contractional relationships, the eastern Hanna Basin exhibits the most complex structural history of any basin in the Rocky Mountain region. Recently mapped, out-of-the-basin thrusting is ubiquitous and magnificently expressed along the margins of adjacent uplifts. Such faulting greatly affects interpretations of local stratigraphy. Incontrovertibly superpositional assemblages of fossil vertebrates have become increasingly important in dating parts of local Paleocene sections, in testing the reliability of North American Land Mammal 'Ages,' and in recognizing the taxonomic nature of transitions from one NALMA to the next. Geological essentials related to paleogeographic interpretations (paleobiological and geological) of basin subdivision will constitute an important introduction to detailed features to be observed in the field.
Principal Localities to be Visited and Topics of Discussion:
Day 1 — 'The Breaks' (northeastern corner of Hanna Basin). Big-picture geologic setting; how to tell an erosional unconformity from a fault; what out-of-the-basin thrust faults look like; problems in documenting such thrusts; nature of local fossil-bearing section; Torrejonian-Tiffanian NALMA transition; geochemical concepts of uranium roll-fronts; taphonomic importance of roll-fronts; recognizing the Paleocene-Eocene boundary globally; and relevance of all this detail to paleobiology.
Day 2 — Margins of Simpson Ridge anticline (east-central Hanna Basin, northwestern Carbon Basin, southeastern Hanna Basin). Big-picture geologic setting; recognition of out-of-the-basin thrusting at multiple scales; significance of stratigraphic curtailment caused by down-section thrust vergence; appreciating blessings of marker beds; recognition of thrusting-related stratigraphic curtailment within largely unexposed sections; interpreting meanings of sudden changes in stratigraphic dip; recognition of overturned strata; coping with geopetal surprises during mapping; judging just where to measure a representative section; view toward eastern edge of Dana klippe and consideration of its paleogeographic significance; and relevance of all this detail to paleobiology.
Day 3 — Along uppermost reaches of Seminoe Reservoir (west-central Hanna Basin). Big-picture geologic setting; viewing a gloriously undeformed and unequivocally superposed, fossil-rich section; Lancian-Puercan boundary and its global implications; validity of subdivisions of Puercan NALMA; regional and more distant paleogeography of Puercan NALMA (faunal alliances with Denver Basin, Williston Basin, San Juan Basin, Chinese equivalents, etc.); value of such sections to other disciplines within paleobiology (especially invertebrates, palynology, macrofloras); view to western edge of Dana klippe and consideration of its paleogeographic significance; and relevance of all this detail to paleobiology.
Number of participants
Because of the need to keep the group together within a complex terrain, the number of participants must be limited to approximately 35.
Cost per participant
Cost per participant, which will Include transportation in the field, three nights lodging at The Virginian Hotel in Medicine Bow, breakfast and packed lunches (dinner not included), and field guides will be $400. A limited number of scholarships for student members will be available.