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Facies patterns and depositional environments of the Peltura scarabaeoides trilobite biozone sediments, Upper Cambrian Alum Shale Formation, southern Sweden

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dc.contributor.authorNewby, Warren, author
dc.contributor.authorEgenhoff, Sven O., advisor
dc.contributor.authorHannah, Judith L., committee member
dc.contributor.authorvon Fischer, Joseph C., committee member
dc.date.accessioned2007-01-03T08:34:17Z
dc.date.available2007-01-03T08:34:17Z
dc.date.issued2012
dc.description.abstractThe Upper Cambrian-age Peltura Scarabaeoides Biozone represents 2.2m - 5.94m of the Alum Shale in Västergötland, southern Sweden. The Alum Shale succession has historically been characterized as an accumulation of dark, organic-rich "monotonous" mudstones deposited in an anoxic and tranquil setting. However, the results of this study indicate the contrary and will place the Alum Shale alongside many other high-TOC mudstones that document abundance of benthic life and advective sediment transport. Description of continuous thin sections at the microscopic-scale enabled the subdivision of the Peltura scarabaeoides Biozone into four carbonate and three siliciclastic facies. The entire biozone represents an overall shallowing trend that can be sub-divided into eight medium-scale shallowing-upward cycles consisting of intercalated carbonates and siliciclastic mudstones. These medium-scale cycles can further be sub-divided into numerous small-scale shallowing- and deepening-upward siliciclastic mudstone cycles. Time estimates suggest that long eccentricity explains the eight medium-scale cycles whereas the driver of the small-scale cycles remains unclear. Along a shelf transect, the proximal sections contain high energy shell debris and pack- to grainstones that grade into carbonate wackestone and mudstones; the distal sections are composed of dark organic-rich shales. All siliciclastic mudstone facies are characterized by abundant bioturbation, with more proximal types being horizontal and larger, and distal ones multidirectional and smaller. All facies also show signs of bed load transport in the form of irregular laminae or ripple structures. Several millimeter-thick slump units are present in the succession, indicating active tectonic movements in the area. The Peltura scarabaeoides Biozone therefore exemplarily shows that early in the Phanerozoic the deep shelf environment was already colonized by a variety of organisms burrowing millimeters into the soft substrate. Silt transported from the shoreline by currents reached even the most distal parts of this shelf. Therefore, the Cambrian deep shelves must have already presented an environment similar to later Paleozoic examples with probably dysoxic to oxic, not anoxic conditions controlling the accumulation of high-TOC sediments.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.identifierNewby_colostate_0053N_11483.pdf
dc.identifierETDF2012400441GEOS
dc.identifier.urihttp://hdl.handle.net/10217/74536
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2000-2019
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.
dc.subjectalum shale
dc.subjectPeltura scarabaeoides
dc.titleFacies patterns and depositional environments of the Peltura scarabaeoides trilobite biozone sediments, Upper Cambrian Alum Shale Formation, southern Sweden
dc.typeText
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
thesis.degree.disciplineGeosciences
thesis.degree.grantorColorado State University
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (M.S.)

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