Reflux revisited

Conference · Fri Jan 01 04:00:00 EST 1988

OSTI ID:6591935

Gill, I; Moore, C H; Aharon, P

The samples and data for this project are derived from 22 test holes drilled to a maximum depth of 91 m, and from rock exposures representing the carbonate section through the Miocene. Dolomite on St. Croix exists in a highly localized region of outcrops and subsurface occurrences in a Miocene-Pliocene reef tract and its related facies. Bioclasts in the dolomitic strata commonly show surprisingly good preservation of microstructure, particularly in large benthic forams and coralline algal clasts. The dolomite is stoichiometrically calcium-rich and exists as euhedral rhombs ranging from 2 to 30 ..mu..m in diameter. The surficial dolomitization occurs in reef, lagoonal, and platform facies that rim the predevelopment shoreline of a coastal lagoon. In the subsurface, dolomitized rock follows the lithifield undersurface of the same lagoon. This spatial distribution of dolomitization suggests a causal relationship between the lagoon hydrology and the process of the dolomitization. The preliminary Sr/sup 87//Sr/sup 86/ isotopic composition of the dolomite is 0.70888, which corresponds to Miocene-Pliocene seawater values, and suggests a Miocene-Pliocene age for the dolomitization event. Stable isotopic values average +2.3 o/oo for delta/sup 13/C and +4.1 o/oo for delta/sup 18/O, both relative to the PDB standard. These data imply that dolomitization took place by reflux of Pliocene fluids enriched in /sup 18/O. The dolomitization was confined to a fault-bounded region, and affected reef, lagoonal, and platform carbonates.

• OSTI ID: 6591935
• Report Number(s): CONF-880301-
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
& Exploration
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
AQUATIC ORGANISMS
BENTHOS
BETA DECAY RADIOISOTOPES
BIOGEOCHEMISTRY
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CENOZOIC ERA
CHEMICAL COMPOSITION
CHEMISTRY
DOLOMITE
ELECTRON CAPTURE RADIOISOTOPES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EXPLORATION
FEDERAL REGION II
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOLOGY
HOURS LIVING RADIOISOTOPES
INTERMEDIATE MASS NUCLEI
ISLANDS
ISOMERIC TRANSITION ISOTOPES
ISOTOPE RATIO
ISOTOPES
LESSER ANTILLES
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERAL RESOURCES
MINERALIZATION
MINERALOGY
MINERALS
MIOCENE EPOCH
NATURAL GAS DEPOSITS
NORTH AMERICA
NUCLEI
OXYGEN COMPOUNDS
PETROCHEMISTRY
PETROGENESIS
PETROLEUM DEPOSITS
PETROLEUM GEOLOGY
PLIOCENE EPOCH
RADIOISOTOPES
REEFS
RESOURCES
ROCKS
SEDIMENTARY ROCKS
STABLE ISOTOPES
STRONTIUM 86
STRONTIUM 87
STRONTIUM ISOTOPES
TERTIARY PERIOD
USA
VIRGIN ISLANDS
WEST INDIES