Hydraulic seals and their origin; evidence from the stable isotope geochemistry of dolomites in the Middle Ordovician St. Peter Sandstone, Michigan Basin

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doi: 10.1306/8D2B14A8-171E-11D7-8645000102C1865D
Authors:Winter, Bryce L.; Valley, John W.; Simo, J. A.; Nadon, Gregory C.; Johnson, Clark M.
Author Affiliations:Primary:
University of Wisconsin-Madison, Department of Geology and Geophysics, Madison, WI, United States
Volume Title:AAPG Bulletin
Source:AAPG Bulletin, 79(1), p.30-48. Publisher: American Association of Petroleum Geologists, Tulsa, OK, United States. ISSN: 0149-1423
Publication Date:1995
Note:In English. 33 refs.; illus., incl. strat. col., 1 table, sketch map
Summary:This dolomitization study is well-documented with isotopic measurements from seven wells. Replacive dolomite (grainstone and mudstone protoliths) forms 5-m thick carbonate intervals in the east-central portion of the basin. Δ13C (PCB) systematically ranges from -50/00 at the top of the dolomite to -100/00 at its base. Δ18O (SMOW) ranges from 270/00 at the top to 230/00 at the base showing a similar trend. These data suggest upward migration of dolomitizing fluids with decreasing upward water-rock exchange. This fluid is modelled to contain 4000 ppm dissolved carbon with Δ13C = -270/00. This light carbon value, significantly lighter than overlying Trenton/Black River carbonates or underlying Brazos shale, suggests carbon derivation from organic diagenesis. Dolomite cement in sandstone laminations and filling fractures display similar Δ13C values to adjacent replacive dolomite. Dolomite cement in diagenetically banded quartz sandstone intervals in the central portion of the basin shows Δ13C and Δ18O values of -7 to-80/00 and 17 to 230/00 in one well, -7.5 to -8.50/00 and 17 to 220/00 in a second well, and -4 to -60/00 and 13 to 190/00 in a third well. The dolomitizing fluids for these cements contained less dissolved carbon than the dolomitizing fluid in the east-central portion of the basin. [J.L.W.]
Subjects:Alkaline earth metals; C-13/C-12; Carbon; Carbonate rocks; Carbonatization; Cement; Clastic rocks; Compaction; Cores; Diagenesis; Dolomitization; Dolostone; Fractures; Geochemistry; Glenwood Shale; Isotope ratios; Isotopes; Laminations; Lithofacies; Major elements; Metals; Middle Ordovician; Natural gas; O-18/O-16; Ordovician; Organic carbon; Organic compounds; Overpressure; Oxygen; Paleozoic; Permeability; Petrography; Petroleum; Planar bedding structures; Porosity; Precipitation; Pressure; Pressure solution; Saint Peter Sandstone; Sandstone; Sea water; Sedimentary rocks; Sedimentary structures; Solutes; Sr-87/Sr-86; Stable isotopes; Stratigraphic traps; Strontium; Traps; Variations; Water-rock interaction; Well logs; Michigan; Michigan Basin; Michigan Lower Peninsula; North America; United States; Brazos Shale; Decarboxylation; Evolution; Organic materials
Abstract Numbers:95M/3156
Record ID:1995018493
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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