Diagenetic
Origins of Dolomitized Reservoirs and Limestone Tombstones in the Madison
Limestone,
Katz, David1, Peter Swart2,
Gregor Eberli3, Matthew Buoniconti4, Langhorne Smith5
(1) University of Miami/RSMAS, Miami, FL (2) University of Miami, Miami, FL (3)
University of Miami, RSMAS, Miami, FL (4) Chevron Exploration Technology
Company, San Ramon, (5) New York State Museum, Albany, NY
Integrated sequence stratigraphy and
geochemistry from the Mississippian Madison Limestone has implications for
understanding the origins and distribution of strataform dolomite reservoirs in
carbonates deposited during continental transgressions and in semi-arid
climates. Dolomitized reservoirs of the Madison Limestone occur in mid-to upper
ramp locations in
Strataform dolomite has two origins and
is divided accordingly into finely-crystalline (2-75 µm wide)
dolomud-wackestone lithologies and medium-crystalline (75-200 µm wide)
dolopack-grainstones. The &delta18O,
&delta13C, 87Sr/86Sr and trace element
results from finely-crystalline dolomite suggest it formed from Mississippian
seawater. Geographic variation in the &delta13C values from
transgressive and regressive systems tracts of 2nd-order, composite and
3rd-order sequences document a trend towards depleted values in a landward
direction suggesting that mid-to upper ramp waters had higher alkalinity which
favors dolomitization. Furthermore, the interpretation of restriction and
increased salinity in mid-to-upper ramp waters is indicated by cross-ramp
variation in &delta18O values which show a trend towards more
enriched values in a landward direction.
The paragenesis of the medium-crystalline
dolomite is somewhat different. After initial formation from seawater with
normal marine &delta18O and &delta13C values, it
was slightly modified having developed radiogenic 87Sr/86Sr
ratios during chemical compaction diagenesis of limestone beds in the shallow
to moderate burial environment. In places, there is evidence of deep burial
diagenesis which significantly improved porosity by calcite dissolution.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California