Donald Kenney (
Last Update: Thu Oct 8 01:18:44 2020


The modern Atlantic Ocean apparently started to open around 200 million years ago at the end of the Triassic Period and in the early part of the Jurassic period. Rift Valley deposits from that time are discussed in another writeup. Oddly perhaps, No sedimentary deposits are known in Eastern North America from the 50 or so million years after the ocean started to open. However, beginning in the Early Cretaceous around 130 million years ago, we start to see sediments that were deposited along the Atlantic Margin of North America. The oldest beds are continental lowland deposits -- presumably coastal swamps. These are superseded further East by a patchwork of Upper Cretaceous and later marine and lowland deposits. The general trend is for the oldest deposits to be found furthest West, but there are places where Cretaceous beds lie along the coast and others where Tertiary deposits are found 100km inland from the coast. In most places, the coastal deposits are buried under unfossiliferous recent debris. Since the coastal plane is generally pretty flat, fossiliferous exposures tend to be confined to stream beds, sea cliffs, quarries, canals, and occasionally road cuts. The underlying bedrock consists of metamorphic Iapetus seafloor rocks and possibly some Triassic Basin rocks

The Atlantic Margin beds extend from SouthEastern Massachusetts to Florida. I have -- quite arbitrarily -- excluded most Pleistocene, Holocene and very recent fossiliferous deposits often found in anomalous places such as Canada's Ottawa River Valley and will discuss them in a separate Terrane writeup.

I have also -- again arbitrarily -- excluded deposits along the Gulf Coast similar to those of the Atlantic margin. Those deposits have a more or less uniform stratigraphic terminology that differs from the contemporaneous Atlantic margin deposits. And they serve as a bridge into the Cretaceous Inland Sea deposits of the plains and Rocky Mountain states and provinces. They will be discussed in another writeup.

The Rocks

Ideally, it might be best to put everything into a single table with states across the top from Florida on the left to Massachusetts on the right and geologic age on the vertical axis. But pragmatically that would require a lot of scrolling to get to the right side. So, I'll break this into tractable subsets.

In general, the deposits are unaltered and often poorly consolidated sediments. The terrestrial rocks are siltstones, shales, clays and conglomerates. Fossils consist of a few vertebrate bones and teeth and occasional plant fossils. The marine rocks are shales, sandstones and limestones. Invertebrate fossils are very common. In some places, marine vertebrates and fish teeth and bones are quite common.

New England

Atlantic margin rocks in New England and New York exist only along offshore islands and a small area in SouthEastern Massachusetts. Where present, they are usually buried under glacial debris and are very poorly exposed. Known exposures of Cretaceous beds are on Long Island, Staten Island, Block Island and the Elizabeth Islands near the South side of Cape Cod. Eocene deposits are exposed in SouthEastern Massachusetts. Cretaceous, Miocene and Pleistocene exposures occur on Marthas Vinyard. Pleistocene fossils are found on Nantucket.

New England Formations

Age New York Rhode Island Massachusetts
Pleistocene See Recent See Recent See Recent
Pliocene Unnamed beds on Marthas Vinyard
Miocene Calvert
Eocene unnamed beds
Cretaceous, Upper Unnamed beds Unnamed beds
Cretaceous, Lower Potomac Potomac

New Jersey to Virgina

Atlantic margin beds are found in New Jersey East of a line from the head of Raritan Bay to the Delaware River at Trenton and thence Southward through Wilmington, Delaware, and Maryland through the North central part of the District of Columbia then South to Smithfield, NC.

New Jersey to Virginia Formations

Age New Jersey Delaware Maryland-DC Virginia
Pleistocene See Recent See Recent See Recent
Pliocene Cohansey Sand Lafayette
Pliocene Norfolk
Miocene Kirkwood Sand Unnamed Formation(s) Yorktown
Miocene St Marys
Miocene Choptank
Miocene Calvert
Eocene Shark River Silt
Eocene Manasquan Clay
Eocene Vincentown Nanjemoy
Paleocene-Eocene Aquia
Paleocene Hornerstown Brightseat
Cretaceous, Upper Tinton-Red Bank-Navesink-Mt Laurel Navesink-Mt Laurel Monmouth
Cretaceous, Upper Tinton-Red Bank-Navesink-Mt Laurel Navesink-Mt Laurel Matawan
Cretaceous, Upper Wenonah Magothy
Cretaceous, Upper Marshalltown Marshalltown Severn
Cretaceous, Upper Englishtown Sand Englishtown
Cretaceous, Upper Woodbury Woodbury
Cretaceous, Upper Magothy Merchantville
Cretaceous, Upper Magothy Magothy
Cretaceous, Lower Raritan Potomac Potomac(Raritan)
Cretaceous, Lower Potomac(Patapsco)
Cretaceous, Lower Potomac(Arundel)
Cretaceous, Lower Potomac(Patuxent)

Limestone Fossiliferous (Igneous/Metamorphic)

The Carolinas

The Atlantic Margin formations are found East of the line from Richmond, Virginia to Smithfield, North Carolina. From there the outcrop is offset West to a point SouthWest of Raleigh and then Southwest through Columbia, SC to Augusta, Georgia.

Formations in the Carolinas

Age Formation
Pleistocene See Recent See Recent
Pliocene Bear Bluff Layayette
Pliocene Waccamaw Yorktown
Miocene Duplin,Raysor,Goose Creek St Marys
Miocene Pungo River
Miocene Hawthorn Coosawhatchie,Marks Head,Parachucla
Oligocene,Upper Cooper Chandler Bridge,Ashley
Oligocene,Lower Cooper Suwanee Limestone,Lazaretto Creek
Eocene,Upper Barnwell Tobacco Road Sandstone,Dry Branch,Ocala,Parkers Ferry,Harleyville
Eocene,Middle Castle Hayne,Mcbean,Santee Orangeburg,Cross
Eocene,Middle Trent
Eocene,Middle Warley Hill
Eocene,Middle Congaree sand
Eocene,Lower Black mingo Fourmile Branch
Paleocene Beaufort Snapp,Lang Syne,Williamsburg-Rhems
Paleocene Tuscahoma
Cretaceous, Upper Peedee
Cretaceous, Upper Black Creek
Cretaceous, Upper Middendorf
Cretaceous, Lower Patuxent

Limestone Fossiliferous (Igneous/Metamorphic)


The Atlantic Margin beds are found South of a line from Augusta on the Georgia-South Carolina border West to and beyond Montgomery, Alabama. These beds largely use the same nomenclature as the Gulf Margin beds further West.

Formations in Georgia

Age Formation
Pleistocene See Recent
Miocene Altamaha-Miccosukee
Miocene Chatahoochee
Oligocene Suwanee
Oligocene Irwinton_barnwell-Glendon
Oligocene Irwinton_barnwell-Marianna
Eocene Irwinton_barnwell-Ocala Limestone-Cooper-Sandersville
Eocene Irwinton_barnwell-Ocala Limestone-Twiggs Clay
Eocene Irwinton_barnwell-Ocala Limestone-Tivola
Eocene Irwinton_barnwell Sand-Ocala Limestone-Clinchfield
Eocene Lisbon-McBean-Claiborne
Eocene Tallahatta
Eocene Tuscahoma
Eocene Hatchitigbee
Eocene Nanfalia
Paleocene Huber
Paleocene Porters Creek
Paleocene Clayton
Cretaceous,Upper Providence
Cretaceous,Upper Ripley
Cretaceous,Upper Cusseta sand
Cretaceous,Upper Bluffton
Cretaceous,Upper Eutaw
Cretaceous,Upper Tuscaloosa

Limestone Fossiliferous (Igneous/Metamorphic)


The entire Florida Peninsula including the Panhandle is covered by Atlantic Margin beds.

Florida Formations

Age Florida Peninsula Florida Panhandle
Pleistocene See Recent See Recent
Pleistocene Miami,Key Largo
Pleistocene Anastasia Limestone,Trail Ridge
Pliocene Cypresshead
Pliocene Citronelle
Pliocene Intracoastal Limestone
Pliocene Tamiami
Miocene-Pliocene Yellow River-Red Bay-Jackson Bluff Miccosukee-Bone Valley-Tamiami Limestone-Hawthorne
Miocene Alachua Shoal River,Alum Bluff
Miocene Hawthorne Chipola-Fort Preston-Coosawhatchie-Statenville-Torreya
Miocene St Marks Chatahoochee
Oligocene Arcadia Duncan Church
Oligocene Suwanee Bryam
Oligocene Marianna
Eocene Crystal River Ocala
Eocene Wells-Inglis
Eocene Avon Park Limestone

Limestone Fossiliferous (Igneous/Metamorphic)


Maps and Figures

Geologic Maps

Massachusetts State map (simplified) State map

Rhode Island

Connecticut State maps

New York Generalized Bedrock Geology of NY

Overview of NY Geology

New Jersey Simplified map of NJ

Index to online geology maps of New Jersey

Pennsylvania Simplified map of PA

Digital Geologic map of Pennsylvania


Map of Cretaceous outcrops on C&D Canal (Note, the original link I used was faulty or has vanished. Hopefully this is the same document) -

Maryland Geologic Map


North Carolina Generalized map

Access to detailed maps

South Carolina

Georgia High Resolution map

Florida Generalized map


See Rocks


Copyright 2006-2012 Donald Kenney ( Unless otherwise stated, permission is hereby granted to use any materials on these pages under the Creative Commons License V2.5.

This page will have been validated as Valid HTML 4.01 Transitional prior to posting on the web site. W3C Logo Image omitted.