Show simple item record

dc.contributor.advisorSchmitt, James
dc.contributor.authorYamamura, Daigo
dc.descriptionAbstract Onlyen_US
dc.description.abstractEnclosing sandstone matrix is often invoked as an entombing medium facilitating preservation of vertebrate skeletal material by isolation from contact with pore fluids. We employed optical petrography, x-ray diffractometry, and scanning electron microscopy analysis of a fossil-bearing sandstone in the Hell Creek Formation to document pore fluid geochemistry during diagenesis. Presence of fine-grained massive muddy sandstone (Sm), abundant coal stringers, and overlying and underlying floodplain mudrocks indicate a crevasse-splay origin. The channel sandstone shows evidence of secondary porosity development through acidic pore fluid migration including feldspar grain skeletonization and complete dissolution, suspended exploded-grain fabrics in biotite indicating dissolution of early calcite cement. The bone-bearing sandstone contains skeletonized and altered feldspar grains also indicating migration of acidic pore-fluids. Enclosed bones show minimal evidence of alteration; they are surrounded by a concretionary zone of calcite and iron oxide cement characterized by isopachous calcite-rims on detrital grains indicating meteoric phreatic calcite precipitation. Presence of well-preserved bone in sandstone extensively altered by acidic fluids suggests that early precipitation of surrounding concretion growth enhanced bone preservation, chemically buffering it from the later corrosive effects of acidic pore waters. This indicates that early concretionary entombment is an important factor in vertebrate skeletal preservation in sandstones.en_US
dc.titleSandstone diagenesis as a proxy indicator of pore fluid geochemistry: implications for fossilization of vertebrate skeletal material in the Hell Creek Formation (Upper Cretaceous), Eastern Montanaen_US
mus.citation.conferenceMSU Student Research Celebration 2012
mus.relation.collegeCollege of Letters & Science
mus.relation.departmentEarth Sciences.en_US
mus.relation.universityMontana State University - Bozemanen_US

Files in this item


This item appears in the following Collection(s)

Show simple item record

MSU uses DSpace software, copyright © 2002-2017  Duraspace. For library collections that are not accessible, we are committed to providing reasonable accommodations and timely access to users with disabilities. For assistance, please submit an accessibility request for library material.