East Berlin Formation

Maroon siltstone, silty and sandy shale, and fine-grained silty sandstone, generally well laminated and commonly well indurated, alternating with dark fissile shale; dolomitic carbonate common in cement, concretions, and thin argillaceous laminae. Local arkose; grades eastward into coarse conglomerate close to eastern border fault. The East Berlin Formation of the Hartford basin contains eight facies: trough cross-bedded sandstones, horizontally stratified sandstones, interbedded sandstones and mudrocks, ripple cross-laminated siltstones, black shales, stratified mudrocks, disrupted shales, and disrupted mudstones. These facies are interpreted as a continental depositional system and are divided into two assemblages. Sandflat/alluvial plain facies assemblage (sandstones and siltstones) is composed of sheet-flood deposits. The lacustrine assemblage (shales and mudrocks) represents a saline lake-playa system (Gierlowski-Kordesch and Rust, 1994).
State Connecticut
Name East Berlin Formation
Geologic age Lower Jurassic
Lithologic constituents
Major
Sedimentary > Clastic > Mudstone > Shalesilty and sandy shale, dark fissile shale
Sedimentary > Clastic > Siltstone
Minor
Sedimentary > Clastic > Sandstonefine-grained silty sandstone
Incidental
Sedimentary > Carbonate > Dolostonedolomitic carbonate common in cement, concretions, and thin argillaceous laminae
Sedimentary > Clastic > Sandstone > ArkoseLocal arkose; grades eastward into coarse conglomerate close to eastern border fault.
Sedimentary > Clastic > Conglomeratecoarse conglomerate close to eastern border fault
Comments Part of Central Lowlands; Newark Terrane - Hartford and Pomperaug Mesozoic Basins. Part of Newark Supergroup (Upper Triassic and Lower Jurassic). Part of ""Meriden Formation"" of Krynine (1950) (Lower Jurassic); CT005. Secondary unit description per CT006.
References

Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 1:125,000.

Krynine, P.D., 1950, Petrology, stratigraphy, and origin of the Triassic sedimentary rocks of Connecticut: Conn. Geol. Nat. History Survey Bull. 73, 239 p.

Gierlowski-Kordesch, Elizabeth and Rust, B.R., 1994, The Jurassic East Berlin Formation, Hartford basin, Newark Supergroup (Connecticut and Massachusetts); a saline lake-playa-alluvial plain system, IN Renaut, R.W., and Last, W.M., eds., Sedimentology and geochemistry of modern and ancient saline lakes: Society of Economic Paleontologists and Mineralogists Special Publication, no. 50, Symposium, Saskatoon, Saskatchewan, August, 1991, p. 249-265, International Geological Correlation Programme (IGCP) Project No. 219/324.

NGMDB product
Counties Hartford - Litchfield - Middlesex - New Haven