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Abstract Detail



Mesozoic and Cenozoic plant evolution and biotic change: A symposium in honor of Ruth Stockey

Smith, Selena Y. [1], Little, Stefan A. [2].

A permineralized, conifer-dominated coastal plant assemblage from the Late Cretaceous Western Interior Seaway of Colorado.

The Western Interior Seaway (WIS) inundated central North America during the mid to late Cretaceous, stretching from the Gulf Coast to Alaska during its largest extent. While much is known about the fauna inhabiting the WIS, little is known about the plant communities on the coastline of this inland sea. Calcareous nodules collected from the Pierre Shale Formation near Colorado Springs, Colorado, were formed in the seaway and preserve remains of plants and invertebrates. The invertebrate fossils place this outcrop in the early Maastrichtian Baculites eliasi ammonite zone. Carbon isotopic analyses of these nodules show that the plant remains were preserved in association with methane cold seep deposits. Nodules were studied using the cellulose acetate peel technique and by complete maceration in order to release plant remains from the surrounding matrix. The floral assemblage is dominated by conifers, represented by rare shoots, five different types of needles, and wood. The majority of the conifer remains are Cupressaceae sensu lato. Angiosperms are represented by fragments of palm stems, rare dicot wood, and several unidentified fruits and seeds. Wood and conifer remains are sometimes charcoalified, pointing to the presence of a fire regime. The least common remains are of various of spore-bearing plants including two types of fern stems, a lycopodialean stem and at least three megaspore morphotypes. This conifer dominated floral assemblage preserved in the WIS contrasts with coeval deposits from compression-impression localities that are typically angiosperm dominated, although Cupressaceae s.l. and other conifers are present. As also demonstrated by previous paleobotanical studies on other shallow marine calcareous nodules, these permineralized fossil assemblages enhance our understanding of Cretaceous and Cenozoic plant diversity and ecosystems.


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1 - University of Michigan, Department of Earth and Environmental Sciences, 2534 CC Little Building, 1100 North University Avenue, Ann Arbor, MI, 48109-1005, USA
2 - Universite Paris-Sud, Laboratoire Ecologie, Systematique, Evolution, CNRS UMR 8079, bat. 360, Orsay, 91405, France

Keywords:
Maastrichtian
Cretaceous
permineralized
Conifer
angiosperm
isotope
Pierre Shale
Western Interior Seaway.

Presentation Type: Colloquium Presentations
Session: C6
Location: Salon 5/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 4:30 PM
Number: C6012
Abstract ID:867
Candidate for Awards:None


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