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Assessing the relationships of the Hell Creek-Fort Union contact, Cretaceous-Paleogene boundary, and Chicxulub impact ejecta horizon at the Hell Creek Formation lectostratotype, Montana, USA

Jason R. Moore, Gregory P. Wilson, Mukul Sharma, Hannah R. Hallock, Dennis R. Braman and Paul R. Renne
Assessing the relationships of the Hell Creek-Fort Union contact, Cretaceous-Paleogene boundary, and Chicxulub impact ejecta horizon at the Hell Creek Formation lectostratotype, Montana, USA (in Through the end Cretaceous in the the type locality of the Hell Creek Formation in Montana and adjacent areas, Gregory P. Wilson (editor), William A. Clemens (editor), John R. Horner (editor) and Joseph H. Hartman (editor))
Special Paper - Geological Society of America (January 2014) 503: 123-135

Abstract

The interval spanning the uppermost Hell Creek Formation to the overlying lowermost Fort Union Formation in north-central Montana encompasses a marked paleoenvironmental change (associated with the formational contact), the Chicxulub impact event, and the Cretaceous-Paleogene boundary. We have examined the record of this transition at the Hell Creek Formation lectostratotype to determine the placement of these events using a series of lithological, geochemical, palynological, and (super 40) Ar/ (super 39) Ar geochronological analyses. The claystone derived from the Chicxulub impact is identified based on lithological criteria, enrichment of iridium and osmium, and osmium isotope ratios. The impact claystone also contains a Cyathidites fern spike. The first continuous lignite horizon in the section immediately overlies this claystone and represents the Hell Creek-Fort Union formational contact. A tuff approximately 3 m above the impact layer is dated to 66.024 + or - 0.059 Ma. Given this evidence, at the lectostratotype the Cretaceous-Paleogene boundary is coincident with the impact claystone and therefore with the formational contact. Due to poor preservation and apparent reworking of palynomorphs surrounding the formational contact, the Cretaceous-Paleogene boundary is difficult to identify based on biostratigraphically significant taxa. The presence of marine dinoflagellates is suggestive of reworking of older marine sediments during the deposition of the Cretaceous-Paleogene boundary interval.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 503
Title: Assessing the relationships of the Hell Creek-Fort Union contact, Cretaceous-Paleogene boundary, and Chicxulub impact ejecta horizon at the Hell Creek Formation lectostratotype, Montana, USA
Title: Through the end Cretaceous in the the type locality of the Hell Creek Formation in Montana and adjacent areas
Author(s): Moore, Jason R.Wilson, Gregory P.Sharma, MukulHallock, Hannah R.Braman, Dennis R.Renne, Paul R.
Author(s): Wilson, Gregory P.editor
Author(s): Clemens, William A.editor
Author(s): Horner, John R.editor
Author(s): Hartman, Joseph H.editor
Affiliation: Dartmouth College, Department of Earth Sciences, Hanover, NH, United States
Affiliation: University of Washington, Department of Biology, Seattle, WA, United States
Pages: 123-135
Published: 201401
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 978-0-8137-2503-1
References: 59
Accession Number: 2015-026144
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch maps
N46°52'60" - N47°58'00", W107°57'00" - W106°04'60"
Secondary Affiliation: University of California, Berkeley, USA, United StatesMontana State University, USA, United StatesUniversity of North Dakota, USA, United StatesUniversity of Washington, USA, United StatesRoyal Tyrrell Museum, CAN, CanadaUniversity of California, Berkeley, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201513
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