65-24 mya

Manasquan Formation

Consists of 30 ft of silty, shelly, fine sands that are commonly glauconitic (Benson and Spoljaric, 1996). Deposited during the latest Paleocene to early Eocene (Benson and Spoljaric, 1996). Based on microfossils (unpublished DGS file data), it can be characterized as an open shelf deposit.

RI75 Stratigraphy and Correlation of the Oligocene to Pleistocene Section at Bethany Beach, Delaware

The Bethany Beach borehole (Qj32-27) provides a nearly continuous record of the Oligocene to Pleistocene formations of eastern Sussex County, Delaware. This 1470-ft-deep, continuously cored hole penetrated Oligocene, Miocene, and Pleistocene stratigraphic units that contain important water-bearing intervals. The resulting detailed data on lithology, ages, and environments make this site an important reference section for the subsurface geology of the region.

What is a fossil?

If you think you may have found a Delaware dinosaur or any unusual fossil, the scientists at the Delaware Geological Survey at the University of Delaware, Newark campus would like to see it. It could provide important information on the geologic history of the First State.

B20 Stratigraphy of the Post-Potomac Cretaceous-Tertiary Rocks of Central Delaware

This Bulletin presents the subsurface stratigraphy of the post-Potomac Cretaceous and Tertiary rocks of the Atlantic Coastal Plain of central Delaware, between the Chesapeake and Delaware (C & D) Canal and Dover. Geophysical log correlations supported by biostratigraphic and lithologic data from boreholes in Delaware and nearby New Jersey provide the basis for the report.

B18 Clay and Clay-Size Mineral Composition of the Cretaceous-Tertiary Section, Test Well Je32-04, Central Delaware

This study complements Delaware Geological Survey Bulletin No. 17 and deals exclusively with clays and clay-size minerals. The cored section at the location of Je32-04 has been subdivided into 25 clay zones on the basis of major changes in trends and degree of crystallinity of clay minerals. The composition of clay minerals varies from zone to zone. These clay minerals have been identified: kaolinite, berthierine, chlorite, illite, smectite, chlorite/smectite, illite/smectite, glauconite/smectite, and glauconite pellets.

B17 Geological Studies of Cretaceous and Tertiary Section, Test Well Je32-04, Central Delaware

A cored well 1,422 feet (433 meters) deep drilled two miles southeast of Dover is the basis for this integrated study of the lithology and paleontology of the Cretaceous-Tertiary section in central Delaware. The section is subdivided into lithostratigraphic, biostratigraphic, chronostratigraphic, and heavy mineral units. Data and results are presented on a common base in three plates.

B13 Geology, Hydrology, and Geophysics of Columbia Sediments in the Middletown-Odessa Area, Delaware

Columbia sediments in the Middletown-Odessa area are composed of boulders, gravels, sands, silts and clays. These sediments are exposed in four gravel pits where their structures and textures were studied. Subsurface geology was interpreted on the basis of the well-log data from 40 holes drilled in the area of study. Columbia sediments were laid upon a surface made up of the greensands of the Rancocas Formation (Paleocene – Eocene age). The contact between the Rancocas and Columbia Formations is an erosional unconformity.

Coastal Plain Rock Units (Stratigraphic Chart)

The geology of Delaware includes parts of two geologic provinces: the Appalachian Piedmont Province and the Atlantic Coastal Plain Province. The Piedmont occurs in the hilly northernmost part of the state and is composed of crystalline metamorphic and igneous rocks. This chart summarizes the age and distribution of the geologic units that are recognized in the state by the Delaware Geological Survey.

Geologic History of the Delaware Coastal Plain

In Delaware, the oldest unit of the Atlantic Coastal Plain is the Potomac Formation. Sediment eroded from the Appalachian Mountains was deposited in rivers and swamps in a tropical climate along the margins of the forming ocean during the latter part of Early Cretaceous time, about 120 million years ago.