The Jurassic East Berlin Formation, Hartford Basin, Newark Supergroup (Connecticut and Massachusetts): A Saline Lake–Playa–Alluvial Plain System
Published:January 01, 1994
Elizabeth Gierlowski-Kordesch, Brian R. Rust, 1994. "The Jurassic East Berlin Formation, Hartford Basin, Newark Supergroup (Connecticut and Massachusetts): A Saline Lake–Playa–Alluvial Plain System", Sedimentology and Geochemistry of Modern and Ancient Saline Lakes Models, Robin W. Renaut, William M. Last
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The Lower Jurassic East Berlin Formation of the Hartford Group (Newark Supergroup), located in the Hartford Basin (Connecticut and Massachusetts), is an alluvial and lacustrine half-graben succession deposited in a semi-arid climate. The formation mainly comprises massive red mudstones, reddish rippled siltstones and shales with minor gray-green mudrocks and shales, black shales, and sheet sandstones. The red mudstones, which contain desiccation cracks up to 1m deep and pedogenic features, are interpreted as fossil vertisols. Like modern analogs in central Australia, these paleosols produced abundant sand-sized mud aggregates that were transported as bedload, and are still recognizable within sandy facies, but were obscured by compaction in the mudstones. Thus, although overwhelmingly muddy, the alluvial system is interpreted as a bedload-dominated distal alluvial plain to sandflat. Sheet sandstones comprise trough cross-stratified sandstone overlain by lineated planar-laminated sandstone or rippled siltstone; all are attributed to sheetfloods, some of which entered the lake.
Lacustrine deposits are represented by stratified gray-green mudrocks and black shales. Sedimentologic, petrologic, and ichnologic evidence all indicate a saline lacustrine paleoenvironment. The lake deposits are associated with disrupted shales that are interpreted as playa sediments. Disrupted shales, interbedded with massive mudstones, show similar vertisol development to the playa muds. The lack of prominent shoreline deposits and large-scale deltaic features is attributed to frequent lake-level fluctuations, which caused extensive migration of the lake shore across distal parts of the uniformly sloping alluvial plain. Major changes in lake level through time in the Hartford Basin are attributed to climatic influences, whereas changes in hydrologie drainage appear to be related to tectonic activity.
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Sedimentology and Geochemistry of Modern and Ancient Saline Lakes Models
Sedimentology and Geochemistry of Modern and Ancient Saline Lakes - This volume of papers grew out of a four-day symposium entitled ?Sedimentary and Paleolimnological Records of Saline Lakes? held at Saskatoon, Canada in August, 1991. The aim of this Special Publication is to bring together selected papers from this conference that deal specifically with the sedimentological, inorganic geochemical, and hydrological aspects of salt lakes and their stratigraphic records. This volume is divided into four sections. The first section contains papers that deal with modern saline lakes. The second section contains papers dealing with sedimentation and diagenesis of late Quaternary salt lakes. The third and fourth sections contain papers devoted to ancient (pre-Quaternary) Lacustrine sequences.