The Glacial and Coastal Geomorphology of Guilford,

Connecticut

Abbie Cooper GE254:Principles of Geomorphology

May 7th, 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?