The Glacial and Coastal Geomorphology of Guilford, Connecticut Abbie Cooper GE254:Principles of Geomorphology May 7 th, 2015

Introduction Located on the Connecticut shoreline in New Haven County Situated in Eastern Highland and Central Lowland regions 13 miles from southernmost to northernmost point 6 miles at widest point Highest point – Bluff Head elevation 720 ft Most heavily populated on shoreline

Bedrock Geology Bolton and Middletown Formations – Metasedimentary and metamorphic gneiss, schist and granite – Pre-Triassic Killingworth, Stony Creek, and Clinton Domes – Coarse grained granite – Pre-Triassic Triassic sediments – Red arkosic sandstones – Conglomerates – Red, grey and black shales

Glacial History Late Pleistocene- continental ice sheets swept across Connecticut at least twice During Late Wisconsinan glaciation, Laurentide ice sheet moved over CT in north- northwest to south-southeast Many of Guilford’s topographic features result from glaciation and glacial retreat

Glacial Impacts Glacial Erosional Features – Striations, grooves, streamlined hills – Orientated N 35°W and N 10° W – Indicative of north- northwest to south- southeast direction of glacial movement

Glacial Impacts Glacial deposits – Till underlies majority of land surface – Erratic boulders – Stratified drift deposited in lakes and streams that resulted from melting glaciers Potato Rock  (a glacial erratic)

Postglacial Coastal Changes Hard Rock Shoreline – formed from resistant rock Beaches and marshes – rare compared to exposed bedrock Beaches are pocket beaches - short stretches of sand between two projecting rock points Tombolo in Joshua Cove connects island to the beach

Uncliffed Headland - Originally rounded by glaciers, have kept their shape despite wave impacts -Photos taken in 1929 and 2015

Sea Level Rise Sea Level of Long Island Sound began to rise as the glaciers melted Over the last 1500 yrs, recorded sea level rise of 2 meters Combined with large storms, causes problems to coastal residents Photo taken after Hurricane Sandy

Summary Much of the shaping and creation of the features that exist in Guilford today took place during glaciation and glacial retreat. Glaciers scored bedrock, deposited material, shaped hills and coastlines. Rising sea levels submerged coastline and created marshes. Sea continues to alter beaches and marshes but not the exposed bedrock.

Questions?