AA SHORTSHORT GEOLOGICALGEOLOGICAL HISTORYHISTORY OFOF BLOCKBLOCK ISLANDISLAND ANDAND RHODERHODE ISLANDISLAND SOUNDSSOUNDS
Ocean Special Area Management Plan
6 January 2009
Jon C. Boothroyd, State Geologist, Rhode Island Geological Survey and Department of Geosciences, College of the Environment and Life Sciences University of Rhode Island [email protected] Ocean SAMP Boundary Generalized Bathymetry – SAMP Area
Battelle, 2004 You are here MALASPINA GLACIER – Northeast Gulf of Alaska
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An Analog “The size of Rhode Island” Ice Flow Directions You are here
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Stone and Sirkin, 1996 End Moraines of Southeastern New England
Schafer and Hartshorn, 1965; Goldsmith, 1982; Sirkin, 1982 End Moraines of Southeastern New England and Long Island
Sirkin, 1982, 1996
Laurentide Ice Retreat
10,000 BP
15,500 BP
24,000 BP
After Dyke & Prest, 1987 Warmer Events in Southern RI Correlated to Greenland GISP‐2 Ice Core
Ice Retreating from - Block Island
Colder Block Island Ice Covered Mohegan Bluffs, BI –Complex Stratigraphy Mohegan Bluffs, BI –Complex Stratigraphy
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Boothroyd and Sirkin, 2002 Mohegan Bluffs, BI –Complex Stratigraphy
LD Lake
LD Till Mohegan Bluffs, BI –Complex Stratigraphy
Eolian Mantle
UD Till
LD Lake Tectonic End Moraines Southern New England
Oldale and O’Hara, 1984 Eastern Shore, BI –Moraine Thrust Slices Deglacial Configuration –BI and RI Sounds
Stone and Borns, 1986 Deglacial Configuration –BI and RI Sounds Glacial Lakes of the Sounds 17,000 BP
E. Uchupi, N.W. Driscoll, R.D. Ballard, and S.T. Bolmer, 2000 Laurentide Eustatic Lakes -10 Sea-Level Laurentide Rise -30 Ice Sheet? 2m.100yr-1
-50
Antarctic Ice Sheet? 2-5m.100yr-1
Fairbanks, 1989 RELATIVE CRUSTAL MOTION Central Long Island Sound
Delayed Not 80m at BI
1989
14C J Radway Stone, 2000 Sea-Level Rise Block Island Sound
- 50 meters
Graphics by BA Oakley; Adapted from P Jordan, RI DEM, 2008 Sea-Level Rise Block Island Sound
Lakes?
- 40 meters Sea-Level Rise Block Island Sound
- 30 meters Sea-Level Rise Block Island Sound
- 20 meters Sea-Level Rise Block Island Sound
- 10- 10 metersmeters Sea-Level Rise Block Island Sound
Present Graphics by BA Oakley; Adapted from P Jordan, RI DEM, 2008 Shoreface Sediment Transport
Barrier Island Transition to Shelf Shoal
Penland, Suter and Boyd 1988 Depositional Platform Platform sandsand sheetsheet
Cross-Shore Swath coarse sand w/small dunes Depositional Pavement cobble gravel Glacial Outcrop boulder gravel concentration
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USGS Seismic Profiles – Block Island Sound
Needell and Lewis, 1984 USGS Seismic End Moraine Profiles ??
Block Island Coastal Plain Sound Sed/Rx Glacial Lake
Needell and Lewis, 1984 USGS ?? Seismic End Moraine Profiles Coastal Block Island Plain Sound Sed/Rx Glacial Lake
Needell and Lewis, 1984 Shelf Shoal ?? End Moraine
Coastal Plain Sed/Rx
Glacial Lake
Needell and Lewis, 1984 Glacial Geology – Narragansett Bay
V.E. 5X
BA Oakley, personal comm, 2008 Summary
• Complex Glacial Topography – End Moraines Deltas and Fans Large Lakes
• Topography Reshaped by Waves and Tidal Current Flow during Sea-Level Rise
• Present Processes – Wave Orbital Motion Downwelling Flow Combined Flow Upwelling Flow
Tidal Current Flow End of Presentation