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Site content related to keyword: "geology"

DGS releases report on subsurface geology of Delaware City area

The Delaware Geological Survey (DGS) has published a report that details new findings on the subsurface geology of the Delaware City area.

Titled Subsurface Geology of the area between Wrangle Hill and Delaware City, Delaware, Report of Investigations Number 78 presents the results of cooperative research between geological consultant John W. Jengo of the firm MWH Americas and DGS researchers Peter P. McLaughlin Jr. and Kelvin W. Ramsey.

RI78 Subsurface Geology of the Area Between Wrangle Hill and Delaware City, Delaware

RI78 Subsurface Geology of the Area Between Wrangle Hill and Delaware City, Delaware

The geology and hydrology of the area between Wrangle Hill and Delaware City, Delaware, have been the focus of numerous studies since the 1950s because of the importance of the local groundwater supply and the potential environmental impact of industrial activity. In this report, 490 boreholes from six decades of drilling provide dense coverage, allowing detailed characterization of the subsurface geologic framework that controls groundwater occurrence and flow.

The region contains a lower section of tabular Cretaceous strata (Potomac, Merchantville, Englishtown, Marshalltown,and Mount Laurel Formations in ascending order) and a more stratigraphically complex upper section of Pleistocene-to-modern units (Columbia, Lynch Heights, and Scotts Corners Formations, latest Pleistocene and Holocene surficial sediments and estuarine deposits). The lowermost Potomac Formation is a mosaic of alluvial facies and includes fluvial channel sands that function as confined aquifer beds; however, the distribution of aquifer-quality sand within the formation is extremely heterogeneous. The Merchantville Formation serves as the most significant confining layer. The Columbia Formation is predominantly sand and functions as an unconfined aquifer over much of the study area.

To delineate the distribution and character of the subsurface formations, densely spaced structural-stratigraphic cross sections were constructed and structural contour maps were created for the top of the Potomac Formation and base of the Columbia Formation. The Cretaceous formations form a series of relatively parallel strata that dip gently (0.4 degrees) to the southeast. These formations are progressively truncated to the north by more flatly dipping Quaternary sediments, except in a narrow north-south oriented belt on the east side of the study area where the deeply incised Reybold paleochannel eroded into the Potomac Formation.

The Reybold paleochannel is one of the most significant geological features in the study area. It is a relatively narrow sandfilled trough defined by deep incision at the base of the Columbia Formation. It reaches depths of more than 110 ft below sea level with a width as narrow as 1,500 ft. It is interpreted to be the result of scour by the sudden release of powerful floodwaters from the north associated with one or more Pleistocene deglaciations. Where the Reybold paleochannel cuts through the Merchantville confining layer, a potential pathway exists for hydrological communication between Columbia and Potomac aquifer sands.

East of the paleochannel, multiple cut-and-fill units within the Pleistocene to Holocene section create a complex geologic framework. The Lynch Heights and Scotts Corners Formations were deposited along the paleo-Delaware River in the late Pleistocene and are commonly eroded into the older Pleistocene Columbia Formation. They are associated with scarps and terraces that represent several generations of sea-level-driven Pleistocene cut-and-fill. They, in turn, have been locally eroded and covered by Holocene marsh and swamp deposits. The Lynch Heights and Scotts Corners Formations include sands that are unconfined aquifers but complicated geometries and short-distance facies changes make their configuration more complex than that of the Columbia Formation.

Number of Pages: 
28

Celebrate Geologic Map Day 2012!

DGS Geologic Map 16

Friday, October 19th has been designated Geologic Map Day 2012. As an extension of the National Cooperative Geologic Mapping Program of USGS, Geologic Map Day focuses the attention of students, teachers, and the general public on the study, uses, and significance of geologic maps for education, science, business, and a variety of public policy concerns.

David R. Wunsch appointed DGS Director

David R. Wunsch appointed DGS Director
Date: Nov 2011

After a nationwide search, David R. Wunsch has been appointed the next Director of the Delaware Geological Survey (DGS) and Delaware State Geologist, effective Nov. 1. He will succeed John H. Talley, who retired on June 30 after more than 38 years of service. Wunsch holds a doctorate in hydrogeology from the University of Kentucky, a master’s degree in geology from the University of Akron, and a bachelor’s degree in geology, with a minor in chemistry, from the State University of New York, Oneonta. In 2011, Wunsch was elected a Fellow of the Geological Society of America. He is an Honorary Member and a past President of the Association of American State Geologists (AASG) and has previously served a term as Secretary of the American Geological Institute.

Wunsch to take helm at DGS

David R. Wunsch, Ph.D.

David R. Wunsch has been appointed the next Director of the Delaware Geological Survey (DGS) and Delaware State Geologist, effective Nov. 1.

DGS honors retiring director, state geologist Talley

Talley is retiring after 38 years of service

John Talley joined the Delaware Geological Survey as a project geologist in 1972, became a senior scientist and hydrogeologist by 1986, and rose to director and state geologist by 2004. He’s consulted with dozens of university, state, and federal governments and groups and amassed a list of more than 50 publications and reports.

DGS Geologic Map No. 17 (Harbeson quadrangle) Dataset

DGS Geologic Map No. 17  (Harbeson quadrangle) 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. 17 (Harbeson quadrangle). The complex geologic history of the surficial units of the Harbeson Quadrangle is that of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene. The geology is further complicated by periglacial activity that produced dune deposits and Carolina Bays scattered throughout the map area.

GM17 Geologic Map of the Harbeson Quadrangle, Delaware

GM17 Geologic Map of the Harbeson Quadrangle, Delaware

The complex geologic history of the surficial units of the Harbeson Quadrangle is one of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene. The geology is further complicated by periglacial activity that produced dune deposits and Carolina Bays scattered throughout the map area.

Map Scale: 
24.000

Delaware Geologic Mapping Program (STATEMAP)

STATEMAP Status Map

The Delaware Geological Survey has a continuing program to map the geology of the entire state at the detailed scale of 1:24,000. The STATEMAP component of the National Cooperative Geologic Mapping Program has contributed significantly to our surficial geologic mapping program. This work has resulted in not only new geologic mapping, but also the digital compilation of previous mapping. Products of this program include file formats that can be downloaded and printed from the web as geologic map products and imported into GIS software as georeferenced layers.

IS7 The Delaware Geological Survey

IS7 The Delaware Geological Survey

IS7 is a foldout brochure that briefly discusses the background and current activities of the DGS. Specifically, the following major programs are listed: Geology, Hydrology, Cartographic Information, Geologic Hazards, Seismograph Network, Outer Continental Shelf, Mineral Resources, Well Records and Sample Library, Publications, and Joint-funded Programs.

SP11 Instructions for Preparation of Delaware Geological Survey Data Base Schedules

SP11 Instructions for Preparation of Delaware Geological Survey Data Base SchedulesInstructions for Preparation of Delaware Geological Survey Data Base Schedules

The DGS, in response to the needs for efficient storage, manipulation,retrieval, and report-generating capability, has proceeded with the conversion of the paper file data base to an integrated automated geologic, hydrologic, and mineral resource management information system. It is necessary to organize data in a systematic and standardized fashion for efficient entry into the automated system. To accomplish this, the DGS has made major revisions in the data recording and filing systems.

This report contains the new DGS data schedules, describes the information that should be recorded on each schedule, and presents instructions for preparation of the schedules. The schedules are designed to make various kinds of data consistent with the input format screens utilized in the automated system.

The types of schedules described include:
1. Well
2. Water Level
3. Lithologic Log
4. Sample
5. Aquifer Test
6. Geophysical Log
7. Field Water Quality
8. Laboratory Water Quality
9. OCS Well

A Generalized Geologic Map of Delaware

Generalized Geologic Map of Delaware

The Delaware Geological Survey (DGS) has published the surficial geology of the state of Delaware at a scale of 1:100,000 for New Castle and Kent counties (Ramsey, 2005, 2007). Maps at this scale are useful for viewing general geologic framework on a county-wide basis, determining the geology of watersheds, and recognizing the relationship of geology to county-wide environmental or land-use issues. These maps, when combined with subsurface geologic information, provide a basis for locating water supplies, mapping ground-water recharge areas, and protecting ground and surface water. Geologic maps are also used to identify geologic hazards, such as flood-prone areas, to identify sand and gravel resources, and for supporting state, county, and local land-use planning decisions. Portions of Sussex County have previously been mapped at 1:24,000-scale.

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DGS releases new geologic map of Georgetown area

The Delaware Geological Survey (DGS) has published a new geologic map of the Georgetown area in eastern Sussex County entitled Geologic Map of the Georgetown Quadrangle, Delaware. Geologic Map No. 15 presents the results of research by Kelvin W. Ramsey of the DGS.

DGS Geologic Map No. 15 (Georgetown Quadrangle) Dataset

DGS Geologic Map No. 15 (Georgetown Quadrangle) Dataset

This vector data set contains the rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map No. 15 (Geologic Map of the Georgetown Quadrangle, Delaware). The geologic history of the surficial geologic units of the Georgetown Quadrangle is primarily that of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition of younger stratigraphic units. The age of the Beaverdam Formation is uncertain due to the lack of age-definitive fossils within the unit but is thought to be between late Pliocene to early Pleistocene in age. Refer to Ramsey, 2010 (DGS Report of Investigations No. 76) for details regarding the stratigraphic units.

To facilitate the GIS community of Delaware and to release the geologic map of the Georgetown Quadrangle with all cartographic elements (including geologic symbology, text, etc.) in a form usable in a GIS, we have released this digital coverage of DGS Geological Map 15. The update of earlier work and mapping of new units is important not only to geologists, but also to hydrologists who wish to understand the distribution of water resources, to engineers who need bedrock information during construction of roads and buildings, to government officials and agencies who are planning for residential and commercial growth, and to citizens who are curious about the bedrock under their homes. Formal names are assigned to all rock units according to the guidelines of the 1983 North American Stratigraphic Code (NACSN, 1983).

GM15 Geologic Map of the Georgetown Quadrangle, Delaware

GM15 Geologic Map of the Georgetown Quadrangle, Delaware

The geologic history of the surficial geologic units of the Georgetown Quadrangle is primarily that of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition of younger stratigraphic units. The age of the Beaverdam Formation is uncertain due to the lack of age-definitive fossils within the unit. Stratigraphic relationships in Delaware indicate that it is no older than late Miocene and no younger than early Pleistocene. Regional correlations based on similarities of depositional style, stratigraphic position, and sediment textures suggest that it is likely late Pliocene in age; correlative with the Bacons Castle Formation of Virginia (Ramsey, 1992, 2010).

Map Scale: 
24,000

DGS Cooperative and Joint-Funded Programs

The DGS is, by statute, the state agency responsible for entering into agreements with its counterpart federal agencies, including the U.S. Geological Survey, the USGS Office of Minerals Information (formerly the U.S. Bureau of Mines), and the Bureau of Ocean Energy Management, Regulation and Enforcement (formerly the U. S. Minerals Management Service), and for administering all cooperative programs of the State with these agencies. The DGS also works with many in-state and out-of-state partner agencies and organizations.

Turtle Branch Formation

Qtb

One to five feet of gray coarse sand and pebbles overlain by one to ten feet of tan to gray clayey silt to silty clay that is in turn overlain by three to five feet of fine to medium sand. Laterally, finer beds are less common away from Marshyhope Creek and the deposit is dominated by fine to medium sand with scattered beds of coarse to very coarse sand with pebbles. Sands are quartzose with some feldspar and laminae of opaque heavy minerals. Underlies a terrace with elevations ranging from 35 to 50 feet and is interpreted to be fluvial to estuarine in origin. Found in the Marshyhope Creek drainage basin in Kent County and more extensively along the Nanticoke drainage basin in Sussex County. Thickness ranges up to 20 feet closer to the valley of the Marshyhope and thins away from the river.

Exploring the Wilmington Blue Rocks: A GeoAdventure in the Delaware Piedmont

Blue Rocks at Greenway

The Wilmington blue rock, Delaware's most famous rock, underlies both the city of Wilmington and the rolling upland north and east of the city. It is best exposed along the banks of the Brandywine Creek from south of Rockland to the Market Street Bridge. Along this section the Brandywine has carved a deep gorge in the blue rock. The water fall along this four mile gorge is approximately 120', and in the 17th and 18th centuries provided water power for one of the greatest industrial developments in the American colonies. The field trip stops described below are chosen as good examples of blue rock along the Brandywine Creek, and to illustrate how the geology has influenced the development of this area. It is not necessary to visit every stop to become familiar with the blue rocks, you may choose to visit only a few.

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