Skip to Main Content
GEOREF RECORD

The sequence stratigraphic and environmental context of primitive vertebrates; Harding Sandstone, Upper Ordovician, Colorado, USA

Jessica L. Allulee and Steven M. Holland
The sequence stratigraphic and environmental context of primitive vertebrates; Harding Sandstone, Upper Ordovician, Colorado, USA
Palaios (December 2005) 20 (6): 518-533

Abstract

The depositional environment of the Upper Ordovician Harding Sandstone of central Colorado has been debated since Charles Walcott first described its pteraspidomorph agnathans. Although most previous workers have favored a marine setting for the Harding based on the presence of marine invertebrates and burrows, some have argued for a fluvial or estuarine habitat for these primitive vertebrates. This study presented here is the first regional, comprehensive analysis of the depositional environments and sequence stratigraphy of the Harding Sandstone. The Harding contains deposits from an array of coastal environments, including transition zone, shoreface, bay/lagoon, washover fan, and bayhead delta. Features of these environments suggest that the Harding was deposited on a microtidal coast with low wave energy. Within the study area, two depositional sequences are developed, and each apparently lacks a lowstand systems tract. The Harding contains numerous flooding surfaces, which preclude any attempt to interpret the Harding as a single depositional environment. Flooding surfaces commonly display evidence of stratigraphic condensation, including burrowed firmgrounds, concentrations of pteraspidomorph plates, and dolomitic cementation. Pteraspidomorph remains are associated most commonly with shoreface facies, are uncommon in bay/lagoon facies, and are absent from bayhead-delta facies. Collectively, these occurrences argue for a shallow-marine habitat for these primitive vertebrates.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 20
Serial Issue: 6
Title: The sequence stratigraphic and environmental context of primitive vertebrates; Harding Sandstone, Upper Ordovician, Colorado, USA
Affiliation: University of Georgia, Department of Geology, Athens, GA, United States
Pages: 518-533
Published: 200512
Text Language: English
Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States
References: 62
Accession Number: 2006-007718
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 plates, 1 table, geol. sketch map
N38°00'00" - N39°00'00", W106°00'00" - W105°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 200604
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal