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Morrison dinosaur taphonomy

From: Ben Creisler

New online article:

Ryan T. Tucker (2011)
Taphonomy of Sheridan College Quarry 1, Buffalo, Wyoming: implications for
reconstructing historic dinosaur localities including Utterback's 1902-1910
Morrison dinosaur expeditions.
Geobios (advance online publication)

The Upper Jurassic Morrison Formation has yielded some of the most
important, voluminous and diverse dinosaur bonebeds in western North
America, yet many of its historic sites were excavated during the
celebrated period of vertebrate paleontology in western North America
referred to as the first and second ?Great Dinosaur Rush? (1870's-1910's).
Because of the large quantity of fossils collected during this era, a
considerable amount of data pertaining to patterns of sedimentation,
preservation, and paleoecology across broad portions of the Morrison
Formation (and indeed many other Mesozoic and Cenozoic units) is still
poorly understood. This paper critically re-evaluates the Sheridan College
Quarry 1 dinosaur bonebed which lies along the western rim of the Powder
River Basin in the region of localities excavated during Utterback's
expeditions in the 1900's. Sedimentologically, the bone bed is interpreted
as having formed by episodic flooding events affecting the proximal
floodplain depocenter of a meandering river system. Limited evidence of
bone abrasion or rounding and progressive upsection changes in bone
orientations suggest that minimal transport occurred, but that at least
four episodes of overbank flooding resulted in the concentration and burial
of attritional, time averaged vertebrate skeletal material that accumulated
in topographic lows on the floodplain. Taphonomic analysis indicates that
multiple unassociated to partially associated fossil elements excavated
represent at least three taxa of sauropod dinosaurs, whereas isolated
elements from the site indicate the presence of several other small
vertebrate taxa. This work provides significant new information not only
about the Sheridan College Quarry 1, but also about local sedimentary and
taphonomic conditions that were likely influential to burial and
preservation of other nearby Morrison dinosaur localities in the Big Horn
Mountains, most notably those excavated during the famous Utterback
expeditions. This study highlights the research potential in reconstructing
lost data for historic dinosaur localities.

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