CROSS, AUREAL T.* AND MYUNG SUK YI. Department of Geological Sciences, Michigan State University, East Lansing, MI 48824-1115 and Department of Geology, Yonsei University, 134 Shinchon-dong Seochemun-Gu, Seoul, 120-749, Korea. - K-T boundary hiatus, Wasatch Plateau environs, Utah, U.S.A.
Stratigraphic distribution of palynomorphs in the Price Canyon and the
Wasatch-Gunnison Plateau region, central Utah are reviewed. Three
floristic assemblages have been documented, indicating a late
Campanian, Maastrichtian, and Lower and Upper Paleocene age for the
stratigraphic units in the Price Canyon section. A hiatus (erosional
or non-depositional) of several million years duration separates
mid-Maastrichtian from early to middle Paleocene strata. Similar gaps
in mammalian and reptilian faunas in successive strata of the Wasatch
and Gunnison Plateau regions are in accord with the stratigraphic
breaks in the palynological record. During early Price River-early
North Horn Formation time, palynological data demonstrate the presence
of coastal margin, fluvial plain, and braid plain sedimentary
environments. Inland lake sedimentation, alternating with broad
floodplain environments, indicate interrupted stream-floodplain
deposition during early middle Paleocene. Later Paleocene and early
Eocene environments were characterized by expanded lake and playa
deposition. Stratigraphic deposition of vertebrate fossils in similar
strata in the Wasatch and Gunnison Plateau areas, including
titanosaurid, ceratopsian, and tyrannosaurid dinosaurs, lizards,
crocodilans, and turtles, are present in the lower and middle
portions of the North Horn Formation. Above this, mammalian faunas
characterize North Horn strata up to about 90 m below the contact with
the Flagstaff Limestone Formation. The earliest Paleocene strata are
characterized by condylarth-dominated faunal assemblages.
Key words: K-T boundary, North Horn Formation, palynology, Utah