This map was created from published 1:100,000-scale geologic maps of New Castle and Kent Counties, and the most current knowledge about the surficial geology of Sussex County. Sussex County was compiled from published 1:24,000-scale geologic maps of various quadrangles and recent fieldwork. (The current version of Sussex County seen here is the same as published in RI76.)

The Delaware Geological Survey (DGS) 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 groundwater 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 a scale of 1:24,000. Field work is in progress in eastern Sussex County and will be complete in the near future.

GIS Methods Used to Create this Map

Heads-up digitizing was performed in ArcGIS from maps on which the geologist drew geologic unit boundaries. Geologic unit boundaries are determined through field interpretation of well and borehole data, aerial photographs, as well as contours from LiDAR. Data compilation methods included merging existing geologic attributes (Ramsey, 1993, 2001, and 2003; Andres and Ramsey, 1995; Schenck et al., 2000), clipping polygons to the state boundary, and extracting and merging the swamp/marsh attribute from the USGS National Hydrography Dataset (NHD). Existing geologic digital data and the NHD are both mapped at a scale of 1:24,000. These areas were designed to be viewed at a scale of 1:100,000 (polygons with an area less than 25,000 square meters were deleted). Base map data (not shown) were compiled for geographic location and editing purposes. Datasets included hydrography, transportation and boundaries for the state of Delaware.  Hydrography data were also generalized to a scale of 1:100,000 using the same method for generalizing the geologic data. A few deleted hydrography polygons were reintegrated into the dataset since they connected stream line data.

The State of Delaware is located within two physiographic provinces, the Appalachian Piedmont and the Atlantic Coastal Plain. Most of the state lies within the Coastal Plain; it is only the hills of northern New Castle County that lie within the Piedmont. Piedmont means foothills. Delaware's rolling hills, which rise to over 400 feet above sea level, are a part of the foothills of the Appalachian Mountains. The rocks at the surface in the Piedmont are old, deformed, metamorphic rocks that were once buried in the core of an ancient mountain range. This range formed early in a series of tectonic events that built the Appalachians between about 543 and 250 million years ago. During an early event, called the Taconic orogeny, an offshore chain of volcanoes collided with the ancient North American continental margin to push up a gigantic mountain range that was as tall as the Alps or the Rockies of today. Geologists date the Taconic orogeny between 470 and 440 million years ago. The Taconic orogeny is important to our understanding of the geology of Delaware, because during this event, the rocks of Delaware's Piedmont were deeply buried under miles of overlying rock and metamorphosed by heat from the underlying mantle. Since that time, rivers and streams have carried the erosional products, mostly sand, clay, and gravel, from the mountains onto the Atlantic Coastal Plain and continental shelf. As the mountains wear down, the buried rocks rebound and rise to the surface. Thus what we see in the Piedmont today are old, deformed, metamorphic rocks that were once buried deep within an ancient mountain range.

The oldest rocks in Delaware also preserve the history of an earlier mountain-building event called the Grenville orogeny. This event occurred approximately one billion years ago. Within Delaware's Piedmont, five distinct rock units can be recognized: (1) rocks of the volcanic arc (Wilmington Complex), (2) rocks formed from the mud and sand deposited in the deep ocean that existed between the volcanic arc and the ancient continental margin (Wissahickon Fm.), (3 & 4) rocks that were once sand and carbonates (calcite and dolomite) lying on the shallow shelf of the ancient continental margin (Setters Fm. and Cockeysville Marble), and (5) rocks of the ancient North American continent (Baltimore Gneiss). The names given to these units indicate the geographic area where they were first identified. Because of the total absence of fossils, determining the age of the Piedmont rocks has always been difficult. Age must be determined either by correlation with units elsewhere in the Piedmont, or by calculating radiometric ages from measurements of radioactive elements and their decay products (usually uranium-lead). Fall Line Delaware's Piedmont ends at the Fall Line where the metamorphic rocks dip under and disappear beneath the sediments of the Coastal Plain. The Fall Line roughly follows Kirkwood Highway, Route 2, across the state between Newark and Wilmington. Parallel to the Fall Line is a narrow zone where rapids and waterfalls are common. Delaware's early settlers built near the rapids using the energy generated from the falls to power their mills. Explorers and sea captains of the colonial period found the bays, rivers, and streams of the Coastal Plain navigable until they reached the fall zone. Here it was necessary to dock their ships, unload the cargo, and move it inland by rail or road. Many of the settlements that grew around these unloading sites later became large cities. Richmond, Washington, Baltimore, Wilmington, and Philadelphia are cities built around ports located along the fall zone. Atlantic Coastal Plain Delaware's Coastal Plain rises to about 100 feet above sea level. Its streams drain into the Delaware River or Bay, and for much of their length they are tidal. The Coastal Plain is made up of sediments, mostly silt, sand, and gravel, that have been eroded off the Piedmont and adjacent Appalachian Mountains. In cross section these sediments form a southeastward thickening wedge that increases from 0 feet at the Fall Line to over 10,000 feet along Delaware's coast. Offshore, on the continental shelf, the sediments become even thicker with reported thicknesses of 8 to 10 miles. In the 1970s and 1980s, exploratory drilling in this thick pile of sediments found no commercial deposits of gas or oil, although one noncommercial gas deposit was discovered. Underlying the sand, silt, and gravel of the Coastal Plain lie consolidated rocks that geologists refer to as the basement. While test drilling into the basement near the Fall Line, metamorphosed and deformed rocks similar to those of the Piedmont were extracted; therefore, the basement is probably a subsurface extension of the Piedmont.

The contact between the sediments of the Coastal Plain and the basement is called an unconformity. An unconformity represents an interval of time during which no sediments are preserved to record geological events. In the Coastal Plain, the oldest sedimentary rocks beneath Delaware's coast are of Late Jurassic to Early Cretaceous age (140-150 million years), and the basement rocks they overlie are of Paleozoic age, older than 245 million years. During the time represented by this unconformity, the rocks we see in the Piedmont today reached the earths surface as approximately 7 to 13 miles of overlying rock were removed by erosion allowing the buried rocks to rise to the surface in compensation. The oldest Coastal Plain sediments observed in Delaware are river-deposited sediments. These sediments were eroded from the Appalachian Mountains to the west, transported to the southeast by rivers, and deposited where the rivers met the ocean to form a delta. On top of the river sediments a sequence of marine silt and sand deposits records the rise and fall of the sea level many times during a period of over 80 million years, from the Late Cretaceous until the end of the Tertiary Period, about 2 million years ago. On top of all of these sediments is a thin veneer of young sand and gravel that was carried into Delaware by glacial outwash during the Ice Age. Glacial ice did not advance into Delaware, but melt-water pouring off the glacier fronts carried great quantities of sand, silt, and gravel over southern Pennsylvania and Delaware. Delaware's largest mineral resource is the sand and gravel deposited from the glacial outwash. Most of the information and figures obtained from SP20 Delaware Piedmont Geology

Sillimanite, a white to tan to green aluminum silicate, (Al₂SiO₅) occurs in high temperature, aluminum-rich metamorphic rocks. In Delaware, it is found in the Hoopes Reservoir and Brandywine Springs areas.

In 1977, the Delaware General Assembly, acting on a proposal by the Delaware Mineralogical Society, established sillimanite as the Delaware State Mineral. This act recognizes the geological and mineralogical significance of the large masses of this mineral found as boulders at Brandywine Springs, an occurrence that was recognized as important in the 6th (1892) edition of Dana's System of Mineralogy. The Brandywine Springs boulders are remarkable for their size and purity. The sillimanite has a fibrous texture reminiscent of wood and could potentially be cut into cabochon gems showing a chatoyant ("cat's eye") effect. Sillimanite is not mined as an ore or raw material In Delaware.

Sillimanite forms at temperatures greater than 550^oC, and its coarse grain size at Brandywine Springs indicates a prolonged period of high-temperature metamorphism of the rocks. These conditions are confirmed by the absence of muscovite and the occurrence of the pair sillimanite + K-feldspar (second sillimanite zone) in the schists/gneisses and by the presence of micropegmatites in the fold noses of the schists/gneisses, which are interpreted as partial melts of the rock under high-temperature conditions.

Delaware Facts and Symbols from Delaware.gov

Belemnite is the common name applied to an extinct order (Belemnoida) of mollusks belonging to the cephalopod class. Modern cephalopods include the squid, octopus, and pearly Nautilus. The belemnoid animal was most closely related to the squid as it had an internal shell covered by a leathery skin, tentacles that pointed forward, and a siphon that expelled water forward thus moving the animal backward by jet propulsion. The internal shell of the belemnoid was cone-shaped and divided into chambers that were gas-filled for maintaining buoyancy in the sea. The chambered shell had a blade-like forward extension that is seldom preserved as a fossil. The most common fossilized part of the internal shell is called the "guard" or "cigar" consisting of a massive, generally brown-colored, subcylindrical structure called the rostrum that encloses the chambered shell and extends to the rear where it tapers to a conical apex. The rostrum served as a counter-weight to the buoyancy provided by the chambered shell and also for protection of that delicate shell. Belemnoids reached their greatest abundance and diversity during the Jurassic and Cretaceous periods. On July 2, 1996, Belemnitella americana was named as the official fossil of Delaware. The Martin Luther King, Jr. Elementary School (Wilmington) third grade Quest students of Kathy Tidball suggested honoring the ancient and noble belemnite as our State fossil.(Delaware Code Title 29 § 314) Belemnites have been found abundantly in the exposures of the Mount Laurel Formation along the banks of the Chesapeake and Delaware Canal in Delaware, east of St. Georges. The fine-grained sands and silts of the Mount Laurel were deposited in a shallow sea during the Late Cretaceous time around 70 million years ago. The fossil belemnite species found here is Belemnitella americana. Sometimes, almost complete belemnite guards can be found, similar in size and shape to a pencil, pointed at one end, but flaring at the other end (if preserved) and partly hollow in the center where the chambered shell was located. Often, only rod-like broken sections of the brown rostrum are found. In Delaware, the best place to look for Belemnitella americana is in the dredge spoil piles on the north side of the Chesapeake and Delaware Canal, just west of St. Georges and also just east of the north side of the Reedy Point Bridge. For more information:

• Belemnites on Wikipedia
• Delaware Facts and Symbols from Delaware.gov

For many years, there has been a question in the minds of some Delawareans as to whether Delaware's highest elevation is Centreville or on Ebright Road.

The Delaware Geological Survey (DGS) at the University of Delaware, through its relationship to the National Geodetic Survey (NGS) has determined that the highest monumented spot in Delaware is located on Ebright Road, near the Pennsylvania state line. Ebright Road is north of Namaans Road, east of route 202.

The Ebright Road benchmark (NGS disk EBRIGHT AZI) was found to be 447.85 feet above sea level. Many people consider Centreville, Delaware to be the highest point in the state; however, a benchmark at Centreville has an elevation of only 445.58 feet making the Ebright Azimuth disk more than two feet higher.

Additional surveying by NGS and DGS personnel and 2007 LiDAR-derived contours indicate that areas just west of Ebright Road are at least two feet higher than the Ebright Azimuth benchmark elevation at around 450 feet. Therefore, according to DGS scientists, the highest actual elevation in Delaware is around 450 feet above sea level. These areas are shown in the map below. The areas within the 450 foot contour lines are highlighted in red.

It's a common misconception that Delaware's High Point at Ebright is the lowest of all US States' high points. This was based on a question in the popular trivia game Trivial Pursuit. In fact, Florida has the lowest high point at 345 feet (Britton Hill, on the Panhandle, near Lakewood.) Actually, Delaware would have the third lowest high point if Washington DC became a state (Fort Reno at 429 feet).

For more information:

• NGS official benchmark data sheet

• Ebright Azimuth Wikipedia entry
• Ebright Azimuth Wikimapia entry
• DelawareOnline: The Backstory on Delaware's Highest Point

The Appalachian Piedmont and Atlantic Coastal Plain are physiographic provinces that are separated by the fall zone. The fall zone (also called the Fall Line) is the contact where the hard crystalline rocks of the Piedmont dip under and disappear beneath the sediments of the Coastal Plain. The landscape and rock types shown in northern Delaware are classical examples of the larger geologic features that dominate the geology of eastern North America. There are reasons why the major cities line up parallel to the coast and in accordance with the trend of the mountains. The fall zone was the limit of navigation to the European explorers. This and the availability of fresh water suggested the location of the initial settlements. Earth materials in the region, stone, sand and gravel, brick and china clay, mica, and feldspar, sustained economic development for several hundred years. Waterpower provided energy essential to the Industrial Revolution. Commerce and communication by ship benefited by access to tidewater. Northeast-southwest land travel and communication benefited from the relatively flat topography of the inner Coastal Plain. No wonder that our initial population concentrated along the fall zone. Delaware's Piedmont provides outstanding illustrations of the influence of geology on our history and society. Our forebears lived close to the land and understood its basic dictates. Pressures of land use and environmental protection now prompt us to rediscover the essentials of geology and apply modern science to advance applications appropriate to today's needs. Image of the Fall Line from the USGS National Atlas: http://nationalatlas.gov/articles/geology/features/fallline.html

The Red Clay Creek has flowed through the rolling hills of northern Delaware for many thousands of years, cutting a deep valley into the old deformed rocks of the Appalachian Piedmont. The Red Clay valley contains many of the common rocks found throughout the Delaware Piedmont.

Igneous Rocks

Igneous rocks are those that form by the crystallization of a hot molten liquid called magma or lava. We can see igneous rocks form today where lava erupts from volcanoes and cools to form solid rock. If it was not for volcanoes, it might be difficult to convince anyone that rocks can form from molten lava. Igneous rocks that form on the Earth’s surface are called volcanic rocks or extrusive igneous rocks.

Not all molten rock rises from deep within the Earth to erupt in a volcano. Sometimes the molten rock, or magma, does not reach the surface, but is held in big underground chambers where it slowly solidifies to form intrusive igneous rocks. We can see this type of igneous rock only where erosion has removed the overlying rocks.

Extrusive and intrusive igneous rocks can be distinguished by the size of their mineral grains. If the individual crystals are too small to be seen without magnification, the rock is fine-grained and probably extrusive. If you can easily differentiate the grains, it is considered coarse-grained and intrusive. Extrusive rocks are fine-grained because lava cools quickly and large grains do not have time to form. Intrusive rocks cool slowly deep inside the Earth and have time to grow large mineral grains.

The igneous rocks exposed in the Red Clay Valley are mostly coarse-grained, intrusive rocks that are named granites, granitic pegmatites, diorites, and gabbros. These rocks form in large masses usually without the layering that is characteristic of sedimentary and metamorphic rocks.

Metamorphic Rocks

Metamorphic rocks are sedimentary or igneous rocks that have been changed. These changes usually occur deep within the Earth, by processes we cannot observe; however, we do know that under the lithosphere the mantle is a slowly churning reservoir of fiery hot rock. Thus, when rocks are deeply buried, they are heated from the reservoir below and squeezed from above by the overlying rocks. At these high temperatures and pressures, some minerals will become unstable and change into new minerals. For example, clay will change into mica, mica plus quartz will change into sillimanite, and chlorite will change into garnet. The mineral changes that occur in solid rocks as they are heated and deeply buried are known as metamorphism.

Common metamorphic rocks are slate, schist, gneiss, quartzite, marble, and amphibolite. The dominant rocks in the Delaware Piedmont are gneisses and amphibolites, rocks that were highly metamorphosed by heating deep within a subduction zone.

Sedimentary Rocks

Sedimentary rocks are made up of the debris from weathering and erosion of rocks, from chemical precipitates, or from the remains of living things. Most sedimentary rocks are formed from particles of older rocks that are carried by rivers and streams to lakes or oceans where they are deposited, deeply buried, and then consolidated into solid rock. They cover most of the ocean floor and three-quarters of the land. The most common solid sedimentary rocks are shale, sandstone, conglomerate, and limestone.

The only sedimentary rocks in Delaware’s Piedmont are modern sediments (sand, silt, and clay) that are being eroded, transported, and deposited in the local streams as the rocks within the watersheds weather and erode. The Piedmont has been a source of sediment that is deposited elsewhere, and has been for a long part of geologic time.

Minerals

At some time almost everyone has picked up and examined a rock. It may have been round and smooth and you liked the way it felt; it may have been just the right size to skip across a pond; or it may have been beautiful or unusual. Whatever your reason for picking up a rock, we hope you observed that it was made up of many small individual grains. These small grains are minerals. Most common everyday rocks, such as granite, slate, or gneiss, are made up of several different minerals, but it is possible for a rock, such as quartzite, to be composed of only one mineral. The dictionary broadly defines a mineral as a naturally occurring solid with a definite chemical composition and an ordered (crystalline) atomic arrangement.

Minerals can form in many ways, such as crystallization from a lava or magma, by recrystallization when a rock is heated or compressed, or by precipitation from water. Usually new minerals crystallize in a medium where they are competing for space with other minerals that are forming at the same time, and they end up as a maze of interlocking grains. However, if the minerals are allowed to crystallize without competition, such as in water or molten magma, the minerals will crystallize into geometric shapes that are strikingly beautiful and often valued by collectors. There are thousands of different minerals that form in the Earth, but only a few are found in the Red Clay Valley.

All of the rock units in Delaware's Piedmont are highly deformed. Deformational features, such as folds, faults, and/or joints, are present in almost every outcrop. The folds are a remarkable assortment of sharp folds, angular crinkle folds, and round gentle folds that may be upright, inclined, or turned upside down. The variety can be attributed to several distinct episodes of folding, and to the different mechanical properties of the rocks. For example, the soft mica-rich gneisses of the Wissahickon were crinkle-folded, whereas during the same deformation the more rigid amphibolites were bent into rounded folds. Overall, the folds in the Piedmont suggest a long compressional event in soft rocks that were hot and deeply buried. Although folding styles in the rocks vary dramatically, the trend of the folds is remarkably consistent across the Piedmont, and parallels the trend of the Appalachians as a whole, which is northeast-southwest. Folds permit determination of tectonic trends and are convenient indicators of crustal movements. Thus the folds in the Piedmont suggest a geologic setting at colliding plate boundaries, and the orientation of the folds indicates convergence from the southeast.

Today in the Delaware Piedmont there are no large active faults. Delaware is positioned on the trailing edge of the North American plate in a moderately active tectonic area. Several hundred million years ago, when Delaware was caught between two colliding plates, deep earthquakes were frequent and probably violent as regional faults stacked the various units in the Piedmont into a high mountain range. These ancient faults are difficult to identify, having been largely obscured by metamorphism and deformation. Faults in cool brittle rocks may offset folds or layering across the fault surface, form a smooth slick surface called a slickenside, or grind up the rocks to produce fault gouge. These indicators of brittle faulting are present in the Piedmont rocks, but they are less common than folds and joints, and are younger features.

Almost all the rocks exposed in Delaware's Piedmont are broken and fractured to form joints. If joints form in deeply buried rocks, they are normally healed with vein material, such as quartz or mixtures of quartz and feldspar. Because the Piedmont rocks were once deeply buried, healed veins are a prominent feature of these rocks. Most of these veins were healed before the major deformational events, and are now folded, stretched into thin layers, or pulled apart into segments. Surface exposures of Wissahickon and Baltimore Gneiss rocks are riddled with very young horizontal and vertical joints, most likely the result of unloading and expansion as the overlying material is removed by erosion. Wilmington Complex rocks will joint and weather by peeling off a curved shell leaving round rocks. This jointing and weathering style is typical of massive, unlayered rocks. Thus, to a first approximation, it is possible to distinguish the rocks of the Wilmington Complex from those of the Wissahickon by the shape of the rocks at the surface. The Wissahickon rocks are angular and sharp whereas the Wilmington Complex rocks are round. The brittle fractures in the Piedmont rocks are important because they provide storage reservoirs for ground water. To produce water, the wells in northern Delaware must tap a fracture zone.

The Piedmont occurs in the hilly northernmost part of the state and is composed of crystalline metamorphic and igneous rocks. These include a variety of rock types that were formed deep in the earth by metamorphic processes, mostly in the early part of the Paleozoic Era (app. 400-500 million years ago), and later uplifted. The rock units of the Wilmington Complex in the Piedmont are subdivided into geologic units called lithodemic units. These bodies of rock are identified by distinctive geological characteristics and are sufficiently thick and areally extensive to be mapped at the earth's surface and/or in the subsurface. Other rock units are mapped as formations. The age of the geologic units that are recognized in the Delaware Piedmont by the Delaware Geological Survey are summarized in the chart below. 

Abbreviations are those used on Delaware Geological Survey maps and cross sections. Geologic time scale not to scale.

For more details (breakdowns) of geologic time, please refer to:

• USGS Divisions of Geologic Time - Major Chronostratigraphic and Geochronologic Units
• Geological Society of America Geologic Time Scale
• Wikipedia - Geologic time scale

Delaware lies within two physiographic provinces, the Appalachian Piedmont and the Atlantic Coastal Plain. The Fall Zone divides these two provinces. The major events in the evolution of the Piedmont rocks occurred between 500 and 200 million years ago.

A great period of time, of which there is no record in Delaware, passed before the deposition of the oldest sediments of the Coastal Plain, the Potomac Formation, during the latter part of Early Cretaceous time, about 120 million years ago. Streams transported clays with interbedded sands from the Appalachian mountains which lay to the northwest and deposited them in rivers and swamps. This process continued into the Late Cretaceous resulting in a wedge of sediments with a thickness of about 4,000 feet in southern Delaware. During the Late Cretaceous, between 100 million and 65 million years ago, sea level rose, and marine sediments were deposited across Delaware. The sands of the Potomac Formation form the Potomac aquifer which provides water to residents of New Castle County.

A small unconformity, or period of nondeposition, separates the Potomac Formation from the overlying Magothy Formation. The white sands and lignitic black silts of the Magothy form a distinctive marker indicating the transition from the older sediments to the later marine deposits.

During the Cenozoic, between 65 million years ago and the present, sea level rose and fell multiple times depositing coastal and marine sediments across a large area of the Delaware Coastal Plain. In Delaware, these deposits are called the Rancocas and Chesapeake Groups. These large stratigraphic groups are subdivided into many formations. The sands in these formations form aquifers which provide water for southern Delaware.

The most recent phase of deposition occurred about 2.4 million years ago when glaciers advanced and retreated across the northern part of North America during the early Pleistocene period. The Beaverdam Formation, which is found over much of southern Delaware, is the result of climate change which transported much of the weathered soils and rocks of the Appalachian Piedmont toward the ocean. The Columbia Formation, which is found in the northern part of the Delaware Coastal Plain, consists primarily of sand with gravel generated by the first glaciers that advanced into the Delaware and Susquehanna River basins. The Beaverdam and Columbia Formations comprise the surficial Columbia aquifer, which provides much of the water for irrigation and domestic wells throughout Kent and Sussex counties.

During the middle to late Pleistocene, sea level rose during warm periods and receded during glacial periods. When sea level was high, (higher than present sea level), sediments were deposited along the margins of the Atlantic Ocean and the Delaware River in environments much like those found along the coast today. During the times when the glaciers were at their maximum in central Pennsylvania,northern New Jersey, and Delaware experienced very cold and windy climates which resulted in the formation of permafrost features and sand dunes across much of its area. Sea level has been rising over the last 12,000 years, advancing the shoreline landward.

Total thickness of all coastal plain units is about 8,000 feet (at Fenwick Island).

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. These include a variety of rock types that were formed deep in the earth by metamorphic processes, mostly in the early part of the Paleozoic Era (app. 400-500 million years ago), and later uplifted. The Coastal Plain, a flatter area that comprises most of the state, is underlain by a series of younger layers of sediments, ranging in age from the Cretaceous Period (app. 120 million years ago) to relatively recent. These have been slightly tilted through geologic time, with very minor faulting or folding in places. The rocks and sediment layers of both of Delaware's geologic provinces can be subdivided into geologic units called lithodemic units (for the crystalline rocks) or lithostratigraphic units (for the sedimentary units). These bodies of rock are identified by distinctive geological characteristics and are sufficiently thick and areally extensive to be mapped at the earth's surface and/or in the subsurface. The chart below summarizes the age and distribution of the geologic units that are recognized in the state by the Delaware Geological Survey.

Abbreviations are those used on Delaware Geological Survey maps and cross sections. Geologic time scale not to scale.

For more details (breakdowns) of geologic time, please refer to:

• USGS Divisions of Geologic Time—Major Chronostratigraphic and Geochronologic Units
• Geological Society of America Geologic Time Scale
• Wikipedia - Geologic time scale

Delaware’s water, both ground and surface, is one of its most important natural resources. It is essential for meeting the needs of all segments of our society and for maintaining economic growth and agriculture. At this time, all water used for public and domestic supply and more than 98% of water used for irrigation south of the Chesapeake and Delaware Canal is groundwater. North of the canal, approximately 70% of public water supplies are obtained from four surface-water sources (creeks) and 30% from groundwater resources.

Because of the importance of groundwater to the State, hydrogeologic programs and studies are a major focus of DGS staff. Recent and ongoing efforts include such subjects as ambient and targeted groundwater level and quality monitoring, mapping of aquifer extents and hydraulic properties, assessing the impacts of artificial drainage and wastewater disposal practices, developing methods for remote sensing of groundwater discharge areas, and development of techniques for storage, analysis, and distribution of groundwater information by geographic information systems. The DGS is the lead agency for collection and analysis of data on groundwater levels and stream discharges in Delaware. The importance of water conditions monitoring has been highlighted in the last several years by a series of droughts and floods. We operate and monitor a variety of systems that provide water-conditions data and capture these data in an Oracle-based hydrological data management system. Groundwater conditions are monitored by a statewide water-level monitoring network of 69 wells. In addition, in 1985 the DGS implemented a water level and chloride monitoring program for 25 wells along the Atlantic Coast to evaluate the potential for salt-water intrusion in aquifers used for public and domestic water supplies. Surface-water conditions are tracked for 15 stream-gage and 10 tide-gage stations around the state. The stream-gaging network was begun by the USGS in 1931 and is now operated cooperatively between the DGS and the USGS. DGS staff participate in programs and projects related to surface water resources of Delaware and the Delaware River Basin. For example, the DGS coordinates these efforts for the state and facilitates acquisition of streamflow and tide-gage data for Delaware stakeholders. Staff members have also been principal investigators in multi-disciplinary, multi-agency studies to evaluate the fluxes of water, plant nutrients, and other dissolved and suspended sediments in the Inland Bays and Nanticoke River watersheds. As Delaware's lead earth science agency, the Delaware Geological Survey provides information to inform and educate resource managers and the public to better understand and manage our water resources. The Delaware Geological Survey, by statute, manages and provides liaison for all state-federal projects related to the DGS-USGS Joint-Funded and Partnering Programs.

Data and Graphs about Water in Delaware

• Current Water Conditions Report
• Delaware Geological Survey - US Geological Survey Stream and Tide Gaging Program
• Data and Graphs of Water Level Summaries for Wells for 20+ years or 100+ observations
• Water Level Summary Table for Index Wells with 20+ years of data
• Spreadsheet table of all wells with 4 or more observations
• Weather, Stream, and Tidal data from the Delaware Environmental Observing System (DEOS)
• Stream Gage Height and Discharge Graphs from the United States Geological Survey (USGS)

Because of its "renewability" water is unique among earth resources that sustain and enhance life. No other mineral resource that we extract on a long-term and continuous basis can be counted on for at least some degree of replenishment within a human lifetime. This attribute allows a great deal of flexibility in management of the resource. In Delaware local rainfall, approximately 44" to 46" per year, renews part or all of our water supply on a regular basis. However, not all of the rain that falls is available for use. From this total rainfall must be subtracted the water that evaporates (about 20"/year), the amount that is used by plants (about 3 to 6"/year), and the amount that runs overland to surface streams during storms (about 4 to 5"/year). The remainder, approximately 13" to 15" is Delaware's bank of water for the year. This water is stored in a system of groundwater reservoirs, or aquifers, that underlie most of the state. Not only do these groundwater reservoirs provide water to wells, but thyey also maintain the flow in surface streams during times of no rainfall. Streamflow between rainfall events is nothing more than the discharge of excess groundwater.

Precipitation: Condensed water vapor that falls to the Earth's surface. Most precipitation occurs as rain, but also includes snow, hail, and sleet.

Runoff: The variety of ways by which water moves across the land. This includes both surface runoff and direct runoff. As it flows, the water may seep into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.

Infiltration: The flow of water from the ground surface into the ground. Once infiltrated, the water becomes soil moisture or groundwater.

Groundwater Flow: The flow of water underground, in the vadose zone and aquifers. Subsurface water may return to the surface (e.g. as a spring or by being pumped) or eventually seep into the oceans. Water returns to the land surface at lower elevation than where it infiltrated, under the force of gravity or gravity induced pressures. Groundwater tends to move slowly, and is replenished slowly, so it can remain in aquifers for thousands of years.

Evaporation: The transformation of water from liquid to gas phases as it moves from the ground or bodies of water into the overlying atmosphere. The source of energy for evaporation is primarily solar radiation. Evaporation often implicitly includes transpiration from plants, though together they are specifically referred to as evapotranspiration.

Transpiration: The release of water vapor from plants and soil into the air.

The following table displays the correlation of hydrologic units to geologic units recognized by the Delaware Geological Survey in the Atlantic Coastal Plain. PDF version is also available below.

Groundwater levels recorded in Qb35-08, a 14-foot deep monitoring well located approximately 5 miles west of Laurel, DE show a remarkable response to tropical storms Irene and Lee, which occurred in August and September, 2011, respectively. Groundwater levels and temperatures in Qb35-08 were collected with an automated pressure-temperature datalogger system. At the same time, rainfall and soil moisture data were recorded by the DEOS Laurel Airport station located approximately 5 miles from the well. In the following illustrations daily mean groundwater levels and groundwater temperatures, total daily rainfall, and daily maximum volumetric soil water content are plotted to show how groundwater, rainfall, and soil moisture are related.

Note the two big storms were 6.6 (Irene, August 27-28) and 3.7 (Lee, September 8) inches. In response, groundwater level (gwl) rose more than 9-1/2 feet, with the largest rise occurring after the second storm. Though a 9-1/2- foot rise in groundwater level within a few weeks is remarkable, long term the gwl are within the range of previously observed gwl. The shallowest groundwater levels observed in this well, about 3 feet below land surface, are very common in this part of Delaware and a primary reason why there are very few homes with basements in the area. Daily mean groundwater temperatures do not show a noticeable affect from the storm events. The timing and magnitude of groundwater level rise is related to the rainfall amount and the antecedent maximum daily volumetric water content (VWC) or soil moisture conditions. Prior to the first storm VWC was less than 0.1 indicating a significant soil moisture deficit. Increase of VWC to values above 20 percent (0.2) and onset of gwl rise appear to be strongly correlated with a delay of one day or less. Rates of increase in gwl slow within two days and reverse within 3-4 days after the VWC drops below 20 percent. The rapid rates of rise in VWC and gwl reflect rapid infiltration and groundwater recharge and are consistent with the sandy soil at the DEOS station and sandy aquifer material at the well site. Rapid recharge is one reason why the shallow aquifer is especially vulnerable to pollution from contaminants released at or just beneath land surface. These data provide an example of why it is important to monitor groundwater conditions. Well Qb35-08 is operated by the Delaware Department of Agriculture as part of their Pesticide Compliance Monitoring Network (PCMN, http://dda.delaware.gov/pesticides/gwater.shtml). Construction, maintenance, and instrumentation are done in cooperation with the Delaware Geological Survey. Additional groundwater and well data can be obtained from this web site or from the PCMN web site.

The Water Conditions Summary is an online monthly summary of water conditions in Delaware. Principal factors in determining water conditions are precipitation, streamflow, and groundwater levels in aquifers. Data from rain gages, stream gages, and observation wells located throughout Delaware have been collected and compiled since the 1960s by the Delaware Geological Survey. These data are displayed as hydrographs and are also available for download. In general, water is abundant in Delaware, but supply is restricted by natural geologic conditions in some areas, by contamination in others, and is dependent on precipitation.

• Summary of Water Conditions in Delaware

The description and identification of minerals in Delaware dates from the first quarter of the nineteenth century. During this time, both geologists and amateur mineral collectors have published on the minerals of Delaware including George Carpenter, Issac Lea, James Booth, and Henry duPont. The location of most mineral occurrences in the state occurs in the Delaware Piedmont. This area is comprised on mafic and felsic gneisses and amphibolites of the Wilmington Complex and the metasedimentary gneisses in the Wissahickon, Cockeysville, and Setters formations as well as the migmatitic gneisses and amphibolites of the Baltimore gneiss. The coastal plain contains relatively few mineral localities. These occurrences can be generally divided into those of the oxidizing or oxygen-rich environments of deposition yielding iron oxide deposits and those of reducing or oxygen-poor environments of deposition yielding iron sulfides, phosphates, and carbonates in greensand and organic muds. (Taken from "Minerals of Delaware" by Peter B. Leavens, in 1979, Transactions of the Delaware Academy of Science, 1976, Delaware Academy of Science, Newark, Delaware).

More Information:

For More information about the Delaware Mineralogical Society,  Visit them on Facebook!

Special Note

Invalid Mineral Names and Mineral Symbols (per IMA/CNMMN)

• bronzite = var. of enstatite
• canbyite = hisingerite
• deweylite = mixture of layer silicates
• fibrolite = sillimanite
• garnierite = probably nepouite
• hornblende = amphibole group
• eucoxene = most likely anatase or rutile
• limonite = most likely goethite
• marmolite = most likely chrysotile or lizardite (serpentine group)
• picotite = chrome spinel
• psilomelane = probably romanechite
• serpophite – most likely lizardite (serpentine group)
• wad = mixture of Mn oxides/hydroxides

Greensand is composed primarily of the mineral glauconite -- a potassium, iron, aluminum silicate. In some Delaware greensands, the glauconite content exceeds 90%. The remaining 10% is mainly quartz. In the past, greensand was used in Delaware as an inexpensive fertilizer. The only active greensand mine in the U.S. today is in New Jersey. Once mined, greensand is dried and used as a soil conditioner. Greensand is also used in water softeners primarily to remove iron from the water. Recent research has shown that greensand has the potential for use as a filter of heavy metals from industrial waste water and landfill leachates.

Sand and gravel are essential for supporting and maintaining economic development throughout Delaware. These natural resources are used primarily for aggregate in the productions of concrete for residential, commercial, and industrial buildings, bridge and highway construction, fill for road beds and foundations, water and wastewater treatment facilities, and for replenishment of our Atlantic and Delaware Bay beaches. There are relatively large quantities of sand and gravel in Delaware. Most of these resources occur as surficial or near-surface deposits that form a veneer of sand and gravel with a thickness up to 150-200 ft in the Delaware Coastal Plain. The deposits generally thicken from north to south across Delaware. However, the quantity and quality of the sand and gravel deposits is not evenly distributed throughout Delaware. There are significant quantities of sand deposits in Delaware Bay and off Delaware's Atlantic Coast that have been and will be used for beach replenishment (DGS Report of Investigations No. 63 An Evaluation of Sand Resources, Atlantic Offshore, Delaware).

The U.S. Geological Survey in cooperation with the Delaware Geological Survey compiles sand and gravel production information on an annual basis and reports it in U. S. Geological Survey publication entitled "The U.S. Geological Survey Minerals Yearbook, The Mineral Industry of Delaware." (http://minerals.usgs.gov/minerals/pubs/state/de.html). At this time, there are at least 11 major sand and gravel production operations in Delaware. General locations are shown on the map. The USGS reported that approximately 3.64 million tons of sand and gravel valued at about $24.7 million dollars were mined in Delaware in 2007. The DGS estimates that the quantities of sand and gravel produced from the State's natural resources are typically higher than those reported by the USGS. Reasons for this include: (1) not being certain that all major producers report production to the USGS; (2) state and local government agencies or companies that produce from borrow pits for their own use do not report production; (3) some operations that mine relatively small amounts of sand and gravel may not have been contacted, and, therefore, do not report production; and (4) production of sand from offshore areas for beach replenishment is not included in USGS figures. For example, according to the Delaware Department of Natural Resources and Environmental Control, in 2004 and 2005 approximately 4.4 million tons of sand with an estimated value of $20.3 million was dredged from the Delaware Bay and Atlantic Ocean and placed on beaches along the Delaware Bay and Atlantic Coast. For more general information related to sand and gravel production and use, the reader may refer to American Geological Institute Environmental Series No. 8 entitled "Aggregates and the Environment." This publication provides the general public, educators, and policy makers a better understanding of the aggregates and environmental concerns related to aggregate resources and supplies (http://www.agiweb.org/environment/publications/aggregate.pdf).

Natural hazards are those events in the physical environment that present risks to human life or property. The DGS identifies and investigates natural hazards to help understand the earth systems that present the hazards and determine strategies to prepare for or mitigate the risks. We are active in advising emergency management agencies on natural hazards, and are included in the Delaware Emergency Operations Plan as an agency having a vital role in dealing with floods, northeaster/extratropical storms, droughts, earthquakes, sinkholes, and dam failures. Because of the risk of coastal flooding in southern Delaware, the DGS conducts a program to document the effect of tides and winds on coastal erosion, especially for events with potentially large human impact. One effort as part of this program was a study of historical accounts of the effects of a Category 1 hurricane that swept northward from the Outer Banks of North Carolina, hitting Delaware on October 23, 1878. A storm surge in Delaware Bay raised water levels 6 feet in one hour in some areas, and the highest water levels in the Delaware River at Wilmington were as much as 12 feet above present sea level. More than 100 fatalities were attributed to the hurricane and property damage may have been as much as $150 million in today's currency. This storm may well be the hurricane of record for the Delaware region and provides a worst-case scenario for a modern hurricane.

Northeasters are a natural hazard that affects Delaware. Northeasters are storms with galeforce or stronger winds from the northeast generated by low-pressure systems offshore the U.S. eastern seaboard. These generate storm waves that can result in significant beach erosion. The duration of the storm is considered a critical factor in the severity of the erosion. Two severe northeasters between January 26 and February 6, 1998 brought tropical storm-force wind gusts to the Delaware coast. They produced the third and fourth highest tides measured at Breakwater Harbor near Lewes, high tides of record at the Coast Guard Station at Indian River Inlet and along Indian River at Rosedale Beach, and 20-ft-high waves at a buoy offshore the Delaware-Maryland state line, which caused some overwash of coastal dunes and localized coastal flooding. Few structures were damaged. In contrast, the severity of these storms is dwarfed by the devastating northeaster of March, 1962. Overwash was pervasive along the entire length of the coast; few sand dunes were left intact and barrier islands were essentially flattened. Most structures adjacent to the beach were damaged. However, tides were comparable for these storms; the 1962 storm had five successive high tides that were well above normal, yet the February 1998 storm had several high tides at similar levels as well as low tides that were higher than those of the 1962 storm. The difference in destruction at similar tide levels suggests that wave conditions may have been more severe in the 1962 storm. Given the extensive development of the coastline since 1962, a storm of similar magnitude would today likely cause damage in the billions of dollars and potentially result in human casualties. Assessment of storm event risks and response strategies depends, in part, on a sound understanding of hydrology and geology. The coastal regions of southern Delaware are impacted by coastal erosion and flooding during large storms, and the Piedmont of northern Delaware is susceptible to flash flooding during major rain events. The DGS serves on the Delaware Emergency Management Agency's (DEMA) Emergency Response Task Force for flooding, northeasters, and hurricanes and usually have staff located at the Delaware Emergency Operations Center during storm emergencies. We have recently been involved in the development of the Delaware Environmental Observation System in cooperation with DEMA and the Office of the State Climatologist. As part of this, a Coastal Flood Risk Analysis System has been proposed that will integrate stream-flow and tide-gage data with meteorological information in a network to be used for real-time flood analysis/prediction and emergency planning, response, and recovery operations. Other natural disaster-related activities include the DEMA Northeaster Task Force, the DEMA Technical Assessment Center for Natural Disasters, the DEMA State Hazard Mitigation Team, and advising on development of a statewide Dam Safety Program. Earthquakes are a natural hazard that occur in northern Delaware and adjacent areas of Pennsylvania, Maryland, and New Jersey. Over 550 earthquakes have been documented within 150 miles of Delaware since 1677, and 69 earthquakes have been documented or suspected in Delaware since 1871. Although Delaware does not face the same degree of earthquake hazard as other, more seismically active parts of the county, FEMA and the USGS in 1997 reclassified Delaware from a low seismic risk to a moderate seismic risk. The largest known event in Delaware occurred in the Wilmington area in 1871 with an intensity of VII (Modified Mercalli Scale). In the memory of many Delawareans is the 1973 earthquake, which was a magnitude 3.8 temblor (Modified Mercalli VVI).

Another hazard studied by the DGS is sinkholes. Geologic mapping in the Hockessin area shows an area underlain by marble and other carbonate bearing rocks that are particularly susceptible to sinkhole formation. At the request of the New Castle County government, DGS staff regularly review consultant's reports related to proposed construction activities in carbonate areas. We also have visited and educated concerned citizens when sinkholes have appeared on their property. Our input helps guide the development of relevant ordinances related to land-use planning and construction activities in these carbonate areas.  Depressions in yards may also be debris pits left from the original development of the property.  The State of Delaware and New Castle County have dedicated funding to remediate debris pits. If you believe you have a debris pit, both can assist you in determining the best course of action.
 
Please Contact:
Division of Watershed Stewardship Debris Pit Remediation Program
Phone: 302-834-5555
Fax:  302-834-0692
2430 Old County Road 
Newark, DE 19702

Email: DNREC.Debrispit@state.de.us

Introduction

Hurricane Sandy was a major storm event for the tidal areas of Delaware. As a part of the mission of the Delaware Geological Survey, we have compiled preliminary Delaware tide and stream-level data for Hurricane Sandy and compared them with previous flooding records. The following tables are the result of the compilation. Please note that these data are preliminary and are subject to change as the data are verified. We have also included some rainfall data to show the rainfall distribution throughout the state related to the storm. These data were provided by the Delaware State Climatologists Office (http://climate.udel.edu/) and were collected as part of the Delaware Environmental Operating System (DEOS, http://www.deos.udel.edu/). The following map shows the location of the stream and tide gages and the DEOS stations used in this report.

DEOS Station Storm Precipitation Total Claymont, DE 5.21" Newark (White Clay Creek) 6.05" New Castle 5.73" Glasgow 6.80" Blackbird 8.39" Dover 9.38" Georgetown 7.92" Laurel 8.22" Rehoboth Beach 10.60" Indian River Inlet 10.98" Bethany Beach 7.83" Rainfall data provided by DEOS.

Tidal Flooding

The following table is a summary of the preliminary tidal high water levels produced by Hurricane Sandy. The record high levels prior to Hurricane Sandy, the date of these levels, and the event (storm or hurricane) are shown for comparison. Nine record levels were reached for the tide gages on the Nanticoke River, in the Inland Bays and along the tidal portion of the Delaware River and its tributaries north of the Chesapeake and Delaware Canal. We have also included two NOAA tide gage graphs (at the bottom of this page) from Breakwater Harbor and Reedy Point that show the rise and fall of the tides during the storm. The difference between the predicted tides and the actual tides is the tidal surge that was the result of the storm.

Stream Flooding

Although significant rainfall occurred throughout Delaware and in southeastern Pennsylvania, no new record stream levels were recorded. Flood stage was reached on five of the streams in northern Delaware. The levels shown in the following table are typical for a heavy rainfall event. We have also included three USGS hydrographs (at the bottom of this page) from the Brandywine at Wilmington, Red Clay Creek near Stanton, and White Clay Creek near Newark streamgages that show the rising water levels in the streams during the storm. It is possible or even likely that in areas in the Coastal Plain of Delaware where rainfall was the heaviest that small streams and ditches may have had significant flooding but no stream gages are located in these areas to record the event.

About the gages, stream and tide data

The Delaware Geological Survey (DGS) is actively involved in the monitoring of natural hazards such as stream and tidal flooding that are the result of large storms. The DGS identifies and investigates natural hazards to help understand the earth systems that present the hazards and determine strategies to prepare for or mitigate the risks. We are active in advising both county and state emergency management agencies on natural hazards. The DGS serves on the Delaware Emergency Management Agency’s (DEMA) Emergency Response Task Force for flooding, northeasters, and hurricanes and had staff located at the Delaware Emergency Operations Center during Hurricane Sandy. An important component of monitoring storm events is having a real-time stream and tide gage network. These gages allow for monitoring of flooding during a storm as it happens to provide information to emergency managers and responders regarding areas of flooding and areas that may be flooded given the trends of rising stream or tide levels. The US Geological Survey, in cooperation with the Delaware Geological Survey, through a Federal-State partnership program operates and maintains stream and tide gages throughout Delaware. Funding for operation and maintenance of this partnership program is provided by the Delaware Geological Survey, US Geological Survey, Delaware Department of Natural Resources and Environmental Control, Delaware Emergency Management Agency, City of Wilmington, City of Newark, and United Water Delaware. The National Oceanic and Atmospheric Administration (NOAA) maintains tide gages in the Delaware Bay and River for purposes of navigation safety, environmental stewardship, and environmental assessment and prediction. These gages are an invaluable resource for real-time tidal conditions in the Delaware Bay and River.

Additional Information

• Hurricane Sandy information from the Delaware State Climatologist
• Hurricane Sandy Q&A from UDaily
• Northeast US Crisis Map from Superstorm Sandy (Google)
• NOAA Hurricane Sandy Response Imagery Viewer
• USGS Flood and Tidal Data for Hurricane Sandy, including Storm Tide Mapper

Contact Us

For more information on Delaware flooding due to Hurricane Sandy, please contact Kelvin Ramsey at the Delaware Geological Survey (delgeosurvey@udel.edu, 302-831-2833.) For rainfall totals, please contact the Delaware State Climatologist Office.

The Glossary of Geology (Glossary of Geology, 4th edition, 1997, Edited by Julia A. Jackson: American Geological Institute, Alexandria, VA) defines a fossil as “any remains, trace, or imprint of a plant or animal that has been preserved in the earth’s crust since some past geologic or prehistoric time.” The field of geology involving the study of fossils is called paleontology. Fossils are of great use to geologists in understanding what the earth was like in the distant past and how life has changed through time. They are also a practical tool in the correlation of sedimentary rock layers from one area to another, which is an important part of exploring for petroleum and understanding the underground "plumbing" of groundwater systems.

Fossils can be fun to collect and interesting to study for the amateur, but they also tell geologists about the history of the world and how it was formed. The best time to look for fossils is after a heavy rain, when pieces of shell and fossil may be exposed in the soil. A stick is handy for scratching around in the top layer of soil. Collectors should remember their manners and should enter pits or other privately owned areas only after obtaining the owner's permission.

Delaware Geological Survey Special Publication Nos. 18 & 19 offer helpful hints for fossil identification and collection. These booklets are available by contacting the Survey or through the on-line ordering of DGS publications.

The most common fossils found in Delaware are from the Cretaceous period, and range from 65 to 100 million years in age. Some fossil collecting localities have also been found in central and southern Delaware, with the fossils generally being younger further south in the state. Fossils found in Kent County are commonly 12 to 20 million years old, and those in Sussex County mostly date from less than less than 1 million years.

Only fragmentary remains of dinosaurs have been found in Delaware. All of these have come from the Chesapeake and Delaware Canal, mainly from the spoil piles created by the dredging of the Canal. Various nature groups in Delaware lead trips to the Canal for collecting. Most of the fossils found are those of marine invertebrates (primarily bivalves and gastropods with some remains of sponges, ammonites, and belemnites).

These fossils date to the late Cretaceous (97 to 65 million years ago) and come from the marine sediments of the Marshalltown and Merchantville Formations. Of the dinosaur remains, none have been complete enough for genus and species identification. At least two hadrosaurid (duck-bill dinosaurs such as Maiasaura) teeth have been found. Several toe bones of ornithomimosaur (small and agile theropod predators that look something like plucked ostriches with long tails and arms) dinosaurs and a partial hadrosaurid vertebra have been recovered. In addition to the dinosaur remains, other vertebrate fossils that have been recovered include: teeth of the marine reptiles Mosasaurus, Globidens, and Tylosaurus; part of a jaw and plates (scutes) of the giant crocodile Deinosuchus; a pleisiosaur vertebra; remains of bony fishes; and shell fragments of the turtles Trionyx, Toxochelys, and other forms. One of the most unique remains found in Delaware is that of a neck bone and a wing bone from a pterosaur (a flying reptile).

Sources of Information

There are many excellent books on dinosaurs available at your local library. A very good book on collecting dinosaur fossils in this region is one entitled "Dinosaurs of the East Coast" and was written by David B. Weishampel and Luther Young. It was published in 1996 by The Johns Hopkins University Press. The book is very thorough in describing dinosaur fossil collecting localities from all along the East Coast of North America, the kinds of dinosaurs to be found, and the habitats and lifestyles.

Another fine book on local dinosaurs is written by William B. Gallagher and is entitled "When Dinosaurs Roamed New Jersey." It was published by Rutgers University Press in 1997. It describes the dinosaur fossils that have been found in New Jersey as well as some information about those from Delaware. The information of dinosaurs from Delaware given above comes from these books. For information regarding the Cretaceous fossils from Delaware, the following are available from the Delaware Geological Survey:

• Open File Report No. 21
  "A Guide to Fossil Sharks, Skates, and Rays from the Chesapeake and Delaware Canal Area, Delaware" written by E.M. Lauginiger and E.F. Hartstein in 1983 and reprinted in 1995.
• Special Publication No. 18
  "Cretaceous Fossils from the Chesapeake and Delaware Canal: A Guide for Students and Amateurs" written by E.M. Lauginiger in 1988.
• Special Publication No. 19
  "Delaware: Its Rocks, Minerals, and Fossils" written by D.C. Windish and T.E. Pickett in 1980 and reprinted in 1991 and 1992.
• Special Publication No. 21
  "Geology and Paleontology of the Lower Miocene Pollack Farm Fossil Site, Delaware" edited by R. M. Benson in 1998.

Delaware offers a few sites for fossil collectors, and the Chesapeake and Delaware Canal and the Pollack Farm are first two locations to check out. Much information is known about these two sites. More information is below, including references to DGS publications detailing the areas. Some other locations throughout the state also offer good hunting grounds for fossil collectors. If you know of good sites in Delaware not listed on this page, please feel free to contact us!

Chesapeake and Delaware Canal - Cretaceous Fossils

The Chesapeake and Delaware Canal is likely the best site in Delaware for fossil collecting. When the canal was built, several formations having fossils from the Cretaceous Period (144 to 65 million years ago) were exposed. Fossils found there represent life forms that existed for a good portion of that period of time and that lived in a shallow sea or along the seashore. The fossils include large clam and oyster shells and a pen-shaped fossil called a belemnite. The belemnite species Belemnitella americana is one of the more common fossils from this area and so was designated Delaware's state fossil. It comes from the inside of a squid-like animal that lived in the seas of the Cretaceous Period. Similar fossils are found in New Jersey and in England. Geologists can use this information to correlate geologic rock units in different areas, allowing them to link events in different parts of the world.

Most fossils found in the Canal area are called "steinkerns." These are formed when a shell fills with mud that later hardens. In some cases, the shell then dissolves, although at the Canal many original shells also are preserved. Other fossils commonly found at the Canal include fish and reptile bones, including vertebrae and teeth. Good locations at the Canal to search for fossils are the dredge spoils near St. Georges and at the foundation of the Reedy Point Bridge. The U. S. Army Corps of Engineers has jurisdiction over the Canal lands, and small-scale collecting of fossils for private collections is permitted. It is against federal law to collect fossils from the area to sell. For more information

• Browse our collection of slides of fossils from the C&D Canal
• OFR21 A Guide To Fossil Sharks, Skates, And Rays From The Chesapeake And Delaware Canal Area, Delaware
• SP18 Cretaceous Fossils From The Chesapeake And Delaware Canal: A Guide For Students And Collectors

Pollack Farm - Miocene Fossils

Located in Kent County, Delaware, the Pollack Farm Site was a surprise to many to contain numerous fossils. The fossils discovered range from a simple Arthropod, small insect, to large vertebrates, such as sharks. In 1991, while Delaware Geological Survey staff collected earth minerals during a highway construction, they came across an upper shell bed full of molluscan fossils. As digging continued numerous fossils of various species and phylum were found. The Delaware Geological Survey provides a resource of facts and photos of the numerous fossils found in central Delaware. This site includes links to four main phylum, which lead to fossil photographs containing brief descriptions. For more information

• Browse our collection of slides of fossils from Pollack Farm
• SP21 Geology And Paleontology Of The Lower Miocene Pollack Farm Fossil Site Delaware
• Pollack Farm site from DelDOT

Delaware Mineralogical Society

The Delaware mineralogical Society is a nonprofit organization dedicated to the promotion and education of mineralogy, paleontology and the lapidary arts. They hold regular meetings, an annual rock and mineral show (with numerous fossils for sale, great for kids and collectors alike!), and field trips throughout the state and surrounding area. Refer to their website below for more information.

• Delaware Mineralogical Society

Other Fossil Sites in Delaware

Other locations throughout the state also offer good hunting grounds for fossil collectors. Just south of Dagsboro, where Route 113 crosses Pepper Creek, the collector can find young (less than 2 million year old) marine fossils from the Pleistocene Epoch. At the state sand and gravel pit just south of Middletown on Route 896, plant impressions from the Pleistocene may be found. A variety of Miocene fossils are know from central Delaware. Fossils from the Miocene epoch, approximately 15 million years in age, have been found in the banks of the Coursey and Killen Ponds near Felton. This is addition to the fossils found at Pollack Farm. For more information:

• SP7 Selected Fossil Collecting Locations in Delaware and Minerals in Delaware
• Delaware fossils sites from FossilSites.com
• Nearby sites and fossil descriptions from the Fossil Guy