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Site content related to keyword: "Omar Formation"

GM20 Geologic Map of the Millsboro and Whaleysville Quadrangles, Delaware

GM20 Geologic Map of the Millsboro and Whaleysville Quadrangles, Delaware

The geological history of the surficial units of the Millsboro Quadrangle and
Delaware portion of the Whaleysville Quadrangle was the result of deposition of the
Beaverdam Formation during the late Pliocene and its subsequent modification by
erosion and deposition related to sea-level fluctuations during the Pleistocene and late
Pleistocene upland swamp and bog deposition. The geology at the land surface was then
further modified by periglacial activity that produced dune deposits and Carolina Bays in
the map area. Surficial geologic mapping was conducted using field maps at a scale of
1:12,000 with 2 foot contours. Stratigraphic boundaries drawn at topographic breaks
reflect detailed mapping using contours not shown on this map.

Number of Pages: 
1
Map Scale: 
1:24,000

DGS Geologic Map No. 20 (Millsboro and Whaleysville Quadrangles) Dataset

DGS Geologic Map No. 20 (Millsboro and Whaleysville Quadrangles) Dataset

This vector data set contains the rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map Series No. 20 (Millsboro and Whaleysville Quadrangles). The geological history of the surficial units of the Millsboro Quadrangle and Delaware portion of the Whaleysville Quadrangle was the result of deposition of the Beaverdam Formation during the late Pliocene and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene and late Pleistocene upland swamp and bog deposition. The geology at the land surface was then further modified by periglacial activity that produced dune deposits and Carolina Bays in the map area. Surficial geologic mapping was conducted using field maps at a scale of 1:12,000 with 2 foot contours. Stratigraphic boundaries drawn at topographic breaks reflect detailed mapping using contours not shown on this map. An additional dataset of datapoints used to generate rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map Series No. 20 (Millsboro and Whaleysville Quadrangles) exists for use in conjunction with this dataset.

GM19 Geologic Map of the Frankford and Selbyville Quadrangles, Delaware

GM19 Geologic Map of the Frankford and Selbyville Quadrangles, Delaware

The geological history of the surficial units of the Frankford and Delaware
portion of the Selbyville Quadrangles was the result of deposition of the Beaverdam
Formation during the late Pliocene and its subsequent modification by erosion and
deposition related to sea-level fluctuations during the Pleistocene. The geology at the
land surface was then further modified by periglacial activity that produced dune deposits
in the map area. Surficial geologic mapping was conducted using field maps at a scale of
1:12,000 with 2 foot contours. Stratigraphic boundaries drawn at topographic breaks
reflect detailed mapping using contours not shown on this map.

Number of Pages: 
1
Map Scale: 
24,000

DGS Geologic Map No. 19 (Frankford and Selbyville Quadrangles) Dataset

 DGS Geologic Map No. 19 (Frankford and Selbyville Quadrangles) Dataset

This vector data set contains the rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map Series No. 19 (Frankford and Selbyville Quadrangles). The geological history of the surficial units of the Frankford and Delaware portion of the Selbyville Quadrangles is that of deposition of the Beaverdam Formation during the late Pliocene and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene. The geology at the land surface was then further modified by periglacial activity that produced dune deposits in the map area. Mapping was conducted using field maps at a scale of 1:12,000 with 2 foot contours. Stratigraphic boundaries drawn at topographic breaks reflect detailed mapping related to contours not shown on this map. An additional dataset of datapoints used to generate rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map Series No. 19 (Frankford and Selbyville Quadrangles) exists for use in conjunction with this dataset.

Omar Formation

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The Omar Formation was originally described (Jordan, 1962) as consisting of interbedded, gray to dark gray, quartz sands and silts with bedding ranging from a few inches to more than 10 feet thick. Thin laminae of clay are found within the fine, well-sorted sands. Silt mixed with sand generally contains some plant matter and where dark in color could be considered organic. Sands contain wood fragments, some of which are lignitic.

RI76 Stratigraphy, Correlation, and Depositional Environments of the Middle to Late Pleistocene Interglacial Deposits of Southern Delaware

RI76 Stratigraphy, Correlation, and Depositional Environments of the Middle to Late Pleistocene Interglacial Deposits of Southern Delaware

Rising and highstands of sea level during the middle to late Pleistocene deposited swamp to nearshore sediments along the margins of an ancestral Delaware Bay, Atlantic coastline, and tributaries to an ancestral Chesapeake Bay. These deposits are divided into three lithostratigraphic groups: the Delaware Bay Group, the Assawoman Bay Group (named herein), and the Nanticoke River Group (named herein). The Delaware Bay Group, mapped along the margins of Delaware Bay, is subdivided into the Lynch Heights Formation and the Scotts Corners Formation. The Assawoman Bay Group, recognized inland of Delaware’s Atlantic Coast, is subdivided into the Omar Formation, the Ironshire Formation, and the Sinepuxent Formation. The Nanticoke River Group, found along the margins of the Nanticoke River and its tributaries, is subdivided into the Turtle Branch Formation (named herein) and the Kent Island Formation.

Delaware Bay Group deposits consist of bay-margin coarse sand and gravel that fine upward to silt and silty sand. Beds of organic-rich mud were deposited in tidal marshes. Near the present Atlantic Coast, the Delaware Bay Group includes organic-rich muds and shelly muds deposited in lagoonal environments.

Assawoman Bay Group deposits range from very fine, silty sands to silty clays with shells deposited in back-barrier lagoons, to fine to coarse, well-sorted sands deposited in barriers and spits.

Nanticoke River Group deposits consist of coarse sand and gravel that fine upward to silty clays. Oyster shells are found associated with the clays in the Turtle Branch Formation. Organic-rich clayey silts were deposited in swamps and estuaries. Well-sorted fine sands to gravelly sands were deposited on beaches and tidal flats on the flanks of the ancestral Nanticoke River and its tributaries.

The Lynch Heights, Omar, and Turtle Branch Formations are age-equivalent units associated with highstands of sea level,which occurred at approximately 400,000 and 325,000 yrs B.P. (MIS 11 and 9, respectively). The Scotts Corners, Ironshire, Sinepuxent, and Kent Island Formations are age-equivalent units associated with highstands of sea level, which occurred between 120,000 and 80,000 yrs B.P. (MIS 5e and 5a, respectively).

Number of Pages: 
50

MS6 Cross Section of Pliocene and Quaternary Deposits Along the Atlantic Coast of Delaware

Cross Section of Pliocene and Quaternary Deposits Along the Atlantic Coast of Delaware

Exploration for sand resources for beach nourishment has led to an increase in the amount of geologic data available from areas offshore Delaware's Atlantic Coast. These data are in the form of cores, core logs, and seismic reflection profiles. In order to provide a geologic context for these offshore data, this cross section has been constructed from well and borehole data along Delaware's Atlantic coastline from Cape Henlopen to Fenwick Island. Placing the offshore data in geologic context is important for developing stratigraphic and geographic models for predicting the location of stratigraphic units found offshore that may yield sand suitable for beach nourishment. The units recognized onshore likely extend offshore to where they are truncated by younger units or by the present seafloor.

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

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.

Number of Pages: 
47

RI47 Ages of the Bethany, Beaverdam, and Omar Formations of Southern Delaware

RI47 Ages of the Bethany, Beaverdam, and Omar Formations of Southern Delaware

The microflora of the Bethany formation and the lower part of the Beaverdam Formation is characterized by a Quercus-Carya assemblage, very few non-arboreal pollen, and Pterocarya and Sciadopitys as exotic constituents. This assemblage has much in common with that of the Brandywine Formation of Maryland and the Eastover Formation of Virginia which are of late Miocene or early Pliocene age. The environment of deposition of the Bethany was probably deltaic, and that of the lower Beaverdam fluviatile.

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.

DGS issues report on the geology of Bethany Beach

RI75 Stratigraphy And Correlation Of The Oligocene To Pleistocene Section At Bethany Beach, Delaware

The Delaware Geological Survey (DGS) at the University of Delaware released a report that provides new insights into the underground geology and hydrology of southeastern Sussex County, Delaware. The report, "Stratigraphy and Correlation of the Oligocene to Pleistocene Section at Bethany Beach, Delaware," summarizes the results of geological investigations conducted on a 1,470-foot-deep research borehole drilled at Bethany Beach, Del.