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Title: Time-stratigraphic reconstruction and integration of paleopedologic, sedimentologic, and biotic events (Willwood Formation, lower Eocene, northwest Wyoming, USA)

Abstract

Relative paleosol maturities are inversely proportional to the accumulation rates of the sediment upon which they formed, and are therefore excellent relative indicators of how much geologic time elapsed between any two horizons. An empirically-based model is advanced using paleosol maturities to estimate the relative geologic time separating any stratigraphic levels within the lower Eocene Willwood Formation. The revised Willwood time stratigraphy from this analysis helps evaluate the nature, tempo, and possible causes of three major episodes of mammalian appearance and disappearance. These faunal events are directly correlated with certain aspects of paleosol evolution in the Willwood Formation. That evolution is tied directly to climatic changes and to varying sediment accumulation rates in response to tectonism. The first faunal turnover occurs at the base of the Willwood Formation. It coincides with a major increase in pedogenic maturity, reflecting a major decrease in sediment accumulation rate, and accompanying general climatic warming at about the time of the Paleocene-Eocene boundary. Throughout the remainder of Willwood time, there was a gradual, yet continual, decrease in paleosol maturity and degree of hydromorphy, probably related to the progressive structural elevation of the Owl Creek antiform bounding the south and southeast margins of the Bighorn Basin.more » This gradual decrease was punctuated by two intervals of more significant decline in paleosol maturity and in the incidence of hydromorphic soils. Both intervals are also marked by faunal turnovers. These sedimentologic and biologic events may reflect tectonic, periods when the rate of basin subsidence increased more rapidly. 58 refs., 7 figs., 2 tabs.« less

Authors:
 [1];  [2]
  1. Geological Survey, Denver, CO (United States)
  2. Univ. of Colorado, Boulder (United States)
Publication Date:
OSTI Identifier:
6515894
Resource Type:
Journal Article
Journal Name:
Palaios; (United States)
Additional Journal Information:
Journal Volume: 8:1; Journal ID: ISSN 0883-1351
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; SEDIMENTS; DEPOSITION; CLIMATIC CHANGE; EOCENE EPOCH; GEOLOGIC DEPOSITS; INDICATORS; LEVELS; MATHEMATICAL MODELS; SEDIMENTATION; STRATIGRAPHY; TIME MEASUREMENT; USA; WYOMING; CENOZOIC ERA; DEVELOPED COUNTRIES; GEOLOGIC AGES; GEOLOGY; NORTH AMERICA; TERTIARY PERIOD; 011000* - Coal, Lignite, & Peat- Reserves, Geology, & Exploration

Citation Formats

Brown, T M, and Kraus, M J. Time-stratigraphic reconstruction and integration of paleopedologic, sedimentologic, and biotic events (Willwood Formation, lower Eocene, northwest Wyoming, USA). United States: N. p., 1993. Web.
Brown, T M, & Kraus, M J. Time-stratigraphic reconstruction and integration of paleopedologic, sedimentologic, and biotic events (Willwood Formation, lower Eocene, northwest Wyoming, USA). United States.
Brown, T M, and Kraus, M J. 1993. "Time-stratigraphic reconstruction and integration of paleopedologic, sedimentologic, and biotic events (Willwood Formation, lower Eocene, northwest Wyoming, USA)". United States.
@article{osti_6515894,
title = {Time-stratigraphic reconstruction and integration of paleopedologic, sedimentologic, and biotic events (Willwood Formation, lower Eocene, northwest Wyoming, USA)},
author = {Brown, T M and Kraus, M J},
abstractNote = {Relative paleosol maturities are inversely proportional to the accumulation rates of the sediment upon which they formed, and are therefore excellent relative indicators of how much geologic time elapsed between any two horizons. An empirically-based model is advanced using paleosol maturities to estimate the relative geologic time separating any stratigraphic levels within the lower Eocene Willwood Formation. The revised Willwood time stratigraphy from this analysis helps evaluate the nature, tempo, and possible causes of three major episodes of mammalian appearance and disappearance. These faunal events are directly correlated with certain aspects of paleosol evolution in the Willwood Formation. That evolution is tied directly to climatic changes and to varying sediment accumulation rates in response to tectonism. The first faunal turnover occurs at the base of the Willwood Formation. It coincides with a major increase in pedogenic maturity, reflecting a major decrease in sediment accumulation rate, and accompanying general climatic warming at about the time of the Paleocene-Eocene boundary. Throughout the remainder of Willwood time, there was a gradual, yet continual, decrease in paleosol maturity and degree of hydromorphy, probably related to the progressive structural elevation of the Owl Creek antiform bounding the south and southeast margins of the Bighorn Basin. This gradual decrease was punctuated by two intervals of more significant decline in paleosol maturity and in the incidence of hydromorphic soils. Both intervals are also marked by faunal turnovers. These sedimentologic and biologic events may reflect tectonic, periods when the rate of basin subsidence increased more rapidly. 58 refs., 7 figs., 2 tabs.},
doi = {},
url = {https://www.osti.gov/biblio/6515894}, journal = {Palaios; (United States)},
issn = {0883-1351},
number = ,
volume = 8:1,
place = {United States},
year = {Mon Feb 01 00:00:00 EST 1993},
month = {Mon Feb 01 00:00:00 EST 1993}
}