PERIODIC ANOXIC SHELF IN THE EARLY—MIDDLE ORDOVICIAN TRANSITION: ICHNOSEDIMENTOLOGIC EVIDENCE FROM WEST-CENTRAL UTAH, USA
GONG Yiming Mary L DROSER
1Faculty of Earth Science, China University of Geosciences, Wuhan 430074, China
2Department of Earth Science, University of California, Riverside CA 92521, USA
Ichnosedimentologic evidence of periodic anoxic shelf in the Early—Middle Ordovician transition includes lower ichnodiversity, shallower bioturbation and burrowing depth (? 4 cm), rare domichnia, tiny Chondrites occupying shallower or shallowest tiering, wide distributed nodules of limonite pseudomorphs after pyrite, occurrence of trace fossils being closely associated with the storm event layers, and stratigraphic successions with orbital cyclostratigraphic architecture. We suggest that lower atmospheric oxygen level during the Early Paleozoic, the Ordovician radiation, dramatic transgression and warmer temperatures would result in the periodic anoxia in the Early—Middle Ordovician transition. This episode began at the later Early Ordovician and lasted about 3.4 Ma on the basis of orbital cyclostratigraphy.
About author: GONG Yiming, born in October 1958, graduated from the Department of Geology, Wuhan College of Geology in 1981, received his Ph.D. degree in China University of Geosciences in 1991. Now he is a professor of China University of Geosciences and mainly engaged in sedimentary stratigraphy and ichnology.
Cite this article:
. PERIODIC ANOXIC SHELF IN THE EARLY—MIDDLE ORDOVICIAN TRANSITION: ICHNOSEDIMENTOLOGIC EVIDENCE FROM WEST-CENTRAL UTAH, USA[J]. JOURNAL OF PALAEOGEOGRAPHY, 2002, 4(4): 81-89.
. PERIODIC ANOXIC SHELF IN THE EARLY—MIDDLE ORDOVICIAN TRANSITION: ICHNOSEDIMENTOLOGIC EVIDENCE FROM WEST-CENTRAL UTAH, USA[J]. JOPC, 2002, 4(4): 81-89.
