GUIDE TO THE REDBEDS OF CENTRAL CONNECTICUT By John F. Hubert Alan A. Reed Wayne L. Dowdall J. Michael Gilchrist 1978 FIELD TRIP EASTERN SECTION OF THE SOCIETY OF ECONOMIC PALEONTOLOGISTS AND MINERALOGISTS Contribution No. 32 Department of Geology and Geography University of Massachusetts Amherst, Massachusetts April, 1978 ii iii DEDICATION This guidebook is dedicated to the memory of Paul D. Krynine (1902-1964), superb teacher and researcher at The Pennsylvania State University and the foremost sedimentary petrographer of his day. His pioneering 1950 monograph "Petrology, stratigraphy, and origin of the Triassic sedi­ mentary rocks of Connecticut" provides inspiration and a solid foundation for the subsequent advances in our under­ standing of the sedimentology of the redbed sequence of the Connecticut Valley. iv v TABLE OF CONTENTS DEDICATION • •.....••••...•••••.•.•••....••....•.. e • • • • • • • • • • • • • • • • iii TABLE OF CONTENTS. • • • . • • • • . • . • • . • • • . • . • . • • . • . • • . • • . v LIST OF FIGURES . ..•.•....•.••••.••.•.••..••••.•..••...••••...•..• viii ACKNOWLEDGMENTS . , •• , , ... , , .••• , , ...••• , . , . • • . • . • . • . • . • • . • xi OBJECTIVES OF THE TRIP •..•...•• • . • • . • . • . • . • . • 1 REGIOl'iAL SETTING. • . 1 ABSTRACT OF THE PALEOGEOGRAPHIC HISTORY ..•.•...••••...••....•..•. 5 STOP 1. PORTLAND ARKOSE, DURIIAM •..••...•.••.••...•...•••••••••.. 9 Location. 9 Introduction................................................ 9 Objective of Stop 1 ..... " ................................... 10 Description of the Alluvial-fan Sequence. 10 STOP 2. NEW HAVEN ARKOSE, NORTH HAVEN •••.••••••..•.....•••...•.. 14 Location .................................................... 14 Objectives of Stop 2..................................... 14 Sedimentation on the Braided-river Alluvial Plain........ 17 Caliche Paleosol Profiles •.•.•.•••...•.••.••.•.•.•.•••..•..• 23 pes crip tion of the Caliche. • • . • • . • • • • . • • • • . • . • • • • • 23 Soil Processes and Paleoclimate •••.•...••.....••...••.. 28 Broad Terrane Hypothesis ...••••••••.••.••..•..••...•••....•• 32 Introduction. 32 Modified Concept ....................................... 32 Isolated Basin Hypothesis ••••••••••••••.•••.•••••••••.•• 37 Pomper aug Outlier. 39 Regional Maps of Hartford Basin-Pomperaug Outlier •..•.• 39 vi Page STOP 3. TALCOTT BASALT, MERIDEN ••.••••• . .... ~ .................. 47 Location . ........................ • • ........ · • · · · · • • · • · • · · · · • 4 7 Objectives of Stop 3. ................ 47 Description of the Talcott Basalt at Stop 3. ................ 50 Paleogeography .................... ......................... 50 STOP 4. EAST PEAK OF THE HANGING HILLS OF MERIDEN ••.•.•••••••.•. 54 Location.................................................... 54 Objective of Stop 4......................................... 54 Geology Seen from the Stone·Tower. 54 STOP 5. NEW HAVEN ARKOSE, MERIDEN •.••. .......................... 59 Location.................................................. 59 Objectives of Stop 5...................................... 59 Description of Stop 5....................................... _59 Interpretation of the River-channel Sandstones ••••••••.••••. 63 STOP 6. SHUTTLE MEADOW FORMATION, PLAINVILLE •••••••••.••....•••. 65 Location.................................................... 65 Objectives of Stop 6 ... ~ ............................. ,....... 65 Evidence for La,cus trine Redbeds •••........ ·...•.••.• , • •.• • • . 66 Paleos lopes . ................................... ~ . 70 Paleocurrents............................................... 72 Enigmatic Inclined Surfaces and Elongate Scour •.••••••••..•• 73 Description of Inclined Surfaces .......••••.••••..•.•.• 73 Description of Elongate Scour .••....•••••••••••••.•••.• 75 Interpretation......................................... 75 Limestone.................................................... 76 vii STOP 7. EAST BERLIN FORMATION, CROMWELL ••••••••••...••••.•..•... 77 Location.................................................... 77 Introduction................................................. 77 Lacustrine Black Shale, Gray Mudstone, and Gray Sandstone ................ 79 Symmetrical Lacustrine Cycles. 79 Paleoslopes ............................................. 85 P aleocui·rents. 85 Origin of Laminated Dolomite-Black Shale or Gray Mudstone Couplets •••• 89 Size and Depth of the Perennial Lakes •••••.•••••..•••.• 96 Burial Diagenesis •. 99 LacuS trine Redbeds. • . 99 River-channel Sa-ndstone ..................................... 102 Floodplain Red Mudstone .••••••.•••• 104 Origin of the Color of the Redbeds ••.•••.••••••.•••••.•• 104 Introduction ...... • ............................... 104 Colors in the East Berlin Formation •.•.••...•......••.• 107 Genesis of Hematite Pigment . .. .• .................... 107 REFERENCES CITED . • • • . • • • . 110 ROAD LOG. • . • • • . • . • • • . • . • . • . • . • . • • . 123 viii LIST OF FIGURES Figure 1. Geologic map with location of field trip stops.................. 2 2. Map of basins of the Newark Supergroup.......................... 4 3. Stratigraphy of the Newark, Hartford, and Deerfield Basins and the Pomper aug Outlier •••••.•.. .-. • • • • . • • . • • • . • . • 6 4. Measured sectiori of alluvial-fan facies of .Portland Arkose, Durham . ........................., . 11 5. Measured section of New Haven Arkose, North Haven ........•.•..•• 15 6. Braided-river sandstone and floodplain red mudstone in New Haven Arkose, North Haven............................... 16 · 7. Close-up of braid-bar complex in Figure 6 .••••••...•••..•••..... 16 8. Sketch of braid-bar complex in New Haven Arkose, North Haven .... 18 9. Thickness of cross-bed sets in New Haven Arkose •.•••••...•....•. 19 10. Sketch of braided river with longitudinal bars •.••.••..•••.•...• 21 11. Field and microscopic features of caliche in the New Haven Arkose. 24 12. Caliche profile in New Haven Arkose, North Haven. • • • • • • • • • • • . •. 26 13. Caliche profile in New Haven Arkose, North Haven ••••.•.•••.•••.• 26 14. Measured section of New Haven Ar):cose along I-84, Southington ..•. 27 15. Late Triassic paleoclimatic zones in Gondwanaland and Laurasia ....... ." ....................... •·.................. 31 16. Newark and Hartford Basins as remnants of a former rift valley (broad terrane hypothesis) .•••••••..•••...•.•.••..·. 33 17. Reconstruc.tion of a Newark-Hartford rift valley under the broad terrane hypothesis. • • . •. • • • • . • • • . • • • • • . • . 34 18. Measured section and paleocurrents of New Haven Arkose, Pomperaug River, South Britain .••••••••••.•••...•••.••• 40 19. Fluvial paleocurrents of Late Triassic age in the Hartford Basin and Pomperaug Outlier •••••••.••..•••••... 42 20. River morphology and dispersal patterns for Late Triassic time in the Hartford Basin and Pomperaug Outlier .•..•.• ; ••••..• 43 ix Figure 21. Contour map of maximum thickness of cross-bed sets in Upper Triassic fluvial rocks, .•..••••.•••.•.•.• 44 22. Contour map of mean size of five largest igneous and metamorphic clasts in Upper Triassic f !uvial rocks . ........................................ ~ 45 23. Measured section of Talcott Basalt, Meriden .•.•••..•••.. 48 24. View of Talcott Basalt,. Meriden......................... 49 25. Pillows in Talcott Basalt, Meriden •••.•...•.•..•....••.• 49 26. Views from East Peak of the Hanging Hills of Meriden •..• 55 27. Measured section and paleocurrents of New Haven Arkose, Meriden. • • • • • • • • . • • • • • . • • • • . • • • . • . 60 28. River-channel sandstone and floodplain mudstone in New Haven Arkose, Meriden •...•.•..••...•••• 61 29. Fluvial sequence in New Haven Arkose, Meriden ••.••••.•.• 61 30. Measured section of Shuttle Meadow Formation, Plainville . ............................. ~ . 6 7 31. Lacustrine flaser bedding in Shuttle Meadow Formation, Plainville ................................... 69 32. Scour surface cut in lacustrine red sandstone of Shuttle Meadow Formation, Plainville ••••.••..•..••••.•. 69 33. Inclined surfaces in lacustrine red sandstone in Shuttle Meadow Formation, Plainville •.•......•••..•. 69 34. Paleoslope directions of lake floors in Shuttle Meadow Formation, Plainville •••••.•..•••.•••.•• 71 35. Stratigraphic sections, depositional environments, paleocurrents, and paleoslopes for East Berlin Fo.rma tion . ............... , . 7 8 36. Perennial lake cycle in East Berlin Formation, CrollMell. 81 37. Lacustrine sequence in East Berlin Formation, CroiilYlell. 82 38. Lacustrine gray mudstone with dolomite laminae in East Berlin Formation, Cromwell..................... 83 X Figure 39. Slump sheets in lacustrine gray mudstone ?f East Berlin Formation, CrolllW'ell . ..................• . 83 40. Animal and plant life along the shore-of an East Berlin lake.............................................. 84 41. Lacustrine paleocurrents and paleoslopes for the East Berlin Formation........................ .............. 87 42. Summary of paleocurrent data for East Berlin Formation .•.•....• 88 43. East Berlin paleogeography at a t .ime of a large perennial lake . ............................ ~ . 90 44. Cross section of the rift valley showing formation of lacustrine and diagenetic minerals •.••.•••.•..••...•.•...•• 93· 45~ Petrographic modal analyses of 23 fluvial and lacustrine sandstones in the East Berlin Formation .•..••••••.• 100 46. Paleocurrents for lacustrine redbeds of the East Berlin Formation.......................................... ..... 103 47. Paleocurrents for river