GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 51-8
Presentation Time: 3:30 PM


HAGADORN, James W.1, WHITELEY, Karen R.1, LAHEY, Bonita L.1, HOLM-DENOMA, Christopher S.2 and HENDERSON, Charles M.3, (1)Department of Earth Sciences, Denver Museum of Nature & Science, 2001 Colorado Blvd, Denver, CO 80205, (2)U.S. Geological Survey, Central Mineral and Environmental Resources Science Center, Box 25046 Denver Federal Center, MS-973, Denver, CO 80225, (3)Department of Geoscience, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada,

The Lykins Formation and its equivalents in Colorado, a suite of redbeds and intercalated stromatolitic carbonates, are hypothesized to span the Permian-Triassic Boundary (PTB). To refine understanding of the age and depositional history of these strata, we logged sixteen reference sections through the Lykins and its equivalents, and here present a preliminary chemostratigraphy, detrital zircon geochronology, biostratigraphy and environmental framework for exposures along the Front Range and in southeastern Colorado.

Conodonts, together with other vertebrate, invertebrate, microfossil, and trace fossils, suggest a very shallow to emergent marine origin for the unit’s most substantial carbonates and intercalated gypsum-anhydrite members. Conodonts from the lower Lykins Formation indicate Middle Permian (Guadalupian) deposition for the lower portion of the Lykins. δ13C and 87Sr/86Sr stratigraphy through the unit is internally consistent with deposition of the Lykins across the PTB interval. Youngest concordant detrital zircons do not exclude deposition of the uppermost Lykins Formation during a portion of Early Triassic time. Detrital zircons from the uppermost Lykins and an overlying eolianite unit consist of a complex and highly diverse primary and multi-cycle grain population transported from eastern Laurentia. They include Appalachian, Grenvillian, and Gondwanan terrane signatures, and transport modes that include wind and water. Conodont alteration indices of 1 indicate the unit has a shallow burial history and is amenable to paleomagnetic inquiry. Considered together, these data help better frame the Lykins and its equivalents, providing a springboard for understanding their records of Permian-Triassic events.