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Northeastern Section - 42nd Annual Meeting (12–14 March 2007)

Paper No. 9
Presentation Time: 1:00 PM-4:45 PM

SEDIMENTOLOGY AND STRATIGRAPHY OF CONTINENTAL FACIES ASSOCIATED WITH THE TRANSITION FROM LACUSTRINE TO FLUVIAL DEPOSITIONAL SYSTEMS, HARTFORD RIFT BASIN, CONNECTICUT


DUGGAN, Katie1, DRZEWIECKI, Peter A.1, GIERLOWSKI-KORDESCH, Elizabeth2 and DWYER III, Allen R.1, (1)Environmental Earth Sciences Department, Eastern Connecticut State University, 83 Windham Street, Willimantic, CT 06226, (2)Geological Sciences, Ohio University, 316 Clippinger Labs, Athens, OH 45701-2979, duggank@stu.easternct.edu

Continental strata present in cores from the Lower Jurassic Portland Formation (Hartford Rift Basin, CT) preserve a transition from lacustrine to fluvial deposition that is interpreted to represent a progressive increase in sediment+water supply relative to accommodation growth in the basin. The 45-meter FD30-T core from Hartford, CT contains mudstone-dominated playa and perennial lake facies at the base transitioning upward to sandstone-dominated sheetflood and fluvial facies at the top.

Eight lithofacies are used to define cyclicity in the lower Portland Formation present in the FD30-T core. They include laminated black shale, massive black shale, and thin-bedded gray shale that are interpreted as perennial lake facies. Crinkly-laminated siltstone, cross-bedded sandstone, current-rippled siltstone, mud-cracked red siltstone, and pedogenically-altered siltstone are interpreted as playa and playa-related facies. These facies are used to define high frequency parasequences (1-3 meters thick) based on relative changes in “wetness” of the interpreted environments. Parasequences stack into depositional sequences (6-18 meters thick) that reflect lower frequency fluctuation between perennial lake and playa facies. These sequences are superimposed on an overall shift from lacustrine to fluvial facies.

The overall shift from lacustrine to fluvial facies is interpreted to reflect a decrease in syndepositional tectonic activity along the border faults of this rift basin. A decrease in the accommodation growth associated with decreased fault activity resulted in a shift from a closed hydrologic system characterized by lakes to an open hydrologic system characterized by rivers. Depositional sequences identified in the core are interpreted to be related to higher frequency climate-controlled variations in sediment+water supply to the basin superimposed on the overall trend. Higher-frequency parasequences most likely reflect shorter duration intrabasinal or extrabasinal processes that effect basin hydrology.

Session No. 20--Booth# 18

Sedimentology and Stratigraphy (Posters)
Monday, 12 March 2007: 1:00 PM-4:45 PM
Geological Society of America Abstracts with Programs. Vol. 39, No. 1, p.60
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