Plate 1 Plate 2 Plate 3 Plate 4 Plate 5 STATE GEOLOGICAL AND NATURAL HISTORY SURVEY OF CONNECTICUT A DIVISION OF THE DEPARTMENT OF AGRICULTURE AND NATURAL RESOURCES .. ..._ .. The Bedrock Geology of the Long Hill and Bridgeport Quadrangles WITH MAPS BY WILLIAM PATRICK CROWLEY Maryland Geological Survev 1968 QUADRANGLE REPORT NO. 24 STATE GEOLOGICAL AND NATURAL HISTORY SURVEY OF CONNECTICUT A DIVISION OF THE DEPARTMENT OF AGRICULTURE AND NATURAL REsOURCES HONORABLE JoHN N. DEMPSEY, Governor of Connecticut JosEPH N. GILL, Commissioner of the Department of Agriculture and Natural Resources COMMISSIONERS HoN. JoHN N. DEMPSEY, Governor of Connecticut DR. J. WENDELL BURGER, De'/)<lrtment of Biology, Trinity College DR. RICHARD H. GoonWIN, Department of Botany, Connecticut College DR. JoE WEBB PEOPLES, Department of Geology, Wesleyan University DR. JoHN RODGERS, Department of Geology, Yale University DR. JAMES A. SLATER, Department of Zoology and Entomology, Univer­ sity of Connecticut DIRECTOR JoE WEBB PEoPLES, Ph.D. Wesleyan University, Middletown, Connecticut EDITOR MAP EDITOR Lou WILLIAMS PAGE, Ph.D. HENRY R. ALDRICH, Ph.D. DISTRIBUTION AND EXCHANGE AGENT WALTER BRAHM, State Librarian State Library, Hartford ii CONTENTS Page Abstract 1 Introduction --------------------------------------------------------------------------------------------------------------- 3 Location ----------------------------------------------------------------------------------------------------------------- 3 Topography and drainage ---------------------------------------------------------------------------------- 3 Previous work -------------------------------------------------------------------------------------------------------­ 3 Acknowledgments --------------------------------------------------------------------------------------------­ 4 Regional setting ----------------------------------------------------------------------------------------------------- 6 Procedure in formation description ----------------------------------------------------------------------­ 6 Metamorphic stratigraphy ---------------------------------------------------------------------------------------- 9 Basal group ---------------------------------------------------------------------------------------------------------------­ 9 Newtown Gneiss --------------------------------------------------------------------------------------------------- 9 General discussion ---------------------------------------------------------------------------------------------- 9 Lithology -------------------------------------------------------------------------------------------------------------- 10 Origin -------------------------------------------------------------------------------------------------------------------- 11 Collinsville Formation ---------------------------------------------------------------------------------------- 12 General discussion --------------------------------------------------------------------------------------------­ 12 Lithology ------------------------------------------------------------------------------------------------------------­ 14 Origin -------------------------------------------------------------------------------------------------------------------- 16 Hartland Group ---------------------------------------------------------------------------------------------------------­ 17 The Straits Schist --------------------------------------------------------------------------------------------------- 17 General discussion ---------------------------------------------------------------------------------------------- 17 Lower member ---------------------------------------------------------------------------------------------------­ 17 Upper member ---------------------------------------------------------------------------------------------------­ 19 Origin ------------------------------------------------------------------------------------------------------------------- 21 Trap Falls Formation --------------------------------------------------------------------------------------------­ 21 General discussion ------------------------------------------------------------------------------------------------ 21 Shelton facies ----------------------------------------------------------------------------------------------------- 22 N orthwestem facies -------------------------------------------------------------------------------------------- 24 Origin ------------------------------------------------------------------------------------------------------------------ 28 Southington Mountain Formation -------------------------------------------------------------------------- 28 General discussion ------------------------------------------------------------------------------------------------ 28 Staurolite-schist member ------------------------------------------------------------------------------ 28 Banded-schist member ---------------------------------------------------------------------------------------- 30 Biotite-gneiss member ---------------------------------------------------------------------------------------- 30 Origin -------------------------------------------------------------------------------------------------------------------- 31 Prospect Formation -----------------------------------------------------------------------------------------------­ 31 General discussion --------------------------------------------------------------------------------------------- 31 Pumpkin Ground Member ---------------------------------------------------------------------------------­ 34 Beardsley Gneiss Member ---------------------------------------------------------------------------------­ 35 Golden Hill Schist Member -------------------------------------------------------------------------------- 37 Calcareous member ---------------------------------------------------------------------------------------------- 38 Origin ----------------------------------------------------------------------------------------------------------------- 38 Ansonia Gneiss -------------------------------------------------------------------------------------------------------- 39 General discussion ---------------------------------------------------------------------------------------------- 39 Lithology -------------------------------------------------------------------------------------------------------------­ 40 Origin -------------------------------------------------------------------------------------------------------------------- 40 Stratigraphic units of uncertain relative age ---------------------------------------------------------- 41 Cooks Pond Schist -------------------------------------------------------------------------------------------------­ 41 General discussion ---------------------------------------------------------------------------------------------- 41 Lithology -------------------------------------------------------------------------------------------------------------­ 41 Origin ------------------------------------------------------------------------------------------------------------------ 41 iii -------- -------------------- Orange Formation ------------------------------------------------------------------------------------------------- 41 General Jiscusslon ---------------------------------------------------------------------------------------------- 41 Derby Hill Member -------------------------------------------------------------------------------------------- 43 Oronoque Member ---------------------------------------------------------------------------------------------- 44 Origin -------------------------------------------------------------------------------------------------------------------- 45 Serpentinite in southern Stratford -------------------------------------------------------------------------- 45 Correlation of the metamorphic rocks --------------------------------------------------------------------- 46 Igneous rocks _______________ ------------------------------------- __ -------------------------------------------------------- 51 ·Pinewood Adamellite ---------------------------------------------------------------------------------------------- 51 Rhyo lite porphyry ________ -------------------------------------------------------------------------------------------- 53 Dacite porphyry ------------------------------------------------------------------------------------------------------ 53 The fluorite zone --------------------------------------------------------------------------------------------------- 53 Buttress Diabase ------------------------------------------------------------------------------------------------------ 54 Structural geology -'------------------------------------------------------------------------------------------------------ 54 General statement ---------------------------------------------------------------------------------------------------- 54 Southeastern domain ---------------------------- ----------------------------------- --------------------------------- 55 Bridgeport syncline ---------------------------------------------------------------------------------------------- 55 Shelton anticline -------------------------------------------------------------------------------------------------- 57 Trap Falls syncline ---------------------------------------------------------------------------------------------- 58 Northwestern domain ----------------------------------------------------------------------------------------------