chesapeake bay impact crater

It is one of the best preserved craters in the world and the largest to be found in America. Lithologic and biostratigraphic data from selected cored intervals in three wells (65, 120, and 116) drilled by the VDEQ and three test holes (31, 43, and 44) drilled as part of a regional geothermal study done by the U.S. Department of Energy and Virginia Polytechnic Institute and State University provided additional stratigraphic control. It is one of the best-preserved "wet-target" or marine impact craters, and the second largest impact crater in the U.S. The rubble bed, which we now realize is an impact breccia, fills the crater and forms a thin halo around it, called an ejecta blanket. The crater's structural depression and subsequent structural adjustments since burial have controlled post-impact environmental depositional settings and stratigraphic relations within and among formations and are responsible for the higher subsidence rates in and adjacent to the crater. Special thanks to Theodore B. Samsel III, Brent Banks, Ed Moser, and Kate Schindler for their help in the design of many figures and plates. Nannofossil data from the Jamestown corehole (55) also indicate a late Oligocene to early Miocene age (see app. "Distribution, Origin, and Resource-Management Implications of Ground-Water Salinity Along the Western Margin of the Chesapeake Bay Impact Structure in Eastern Virginia." The Pleistocene scarps were formed by fluvial, estuarine erosion (valley-facing scarps) and shoreline erosion (coast-facing scarps) caused by changes in sea level that occurred during the glacial-interglacial period. "Chesapeake Bay Impact Structure - 35 Million Years After - and Still Making An Impact." Johnson, G.H., 1969, Geology of the lower York-James Peninsula and south bank of the James River: Williamsburg, Va., College of William and Mary, Department of Geology Guidebook 2, 33 p. Johnson, G.H., 1972, Geology of the Yorktown, Poquoson West, and Poquoson East quadrangles, Virginia: Virginia Division of Mineral Resources Report of Investigation 30, 57 p. Johnson, G.H., 1976, Geology of the Mulberry Island, Newport News North, and Hampton quadrangles, Virginia: Virginia Division of Mineral Resources Report of Investigation 41, 72 p. Johnson, G.H., Berquist, C.R., and Ramsey, K., 1980, Guidebook to the late Cenozoic Geology of the lower York-James Peninsula, Virginia: Williamsburg, Va., College of William and Mary, Department of Geology Guidebook 2, 52 p. Johnson, G.H., Berquist, C.R., Ramsey, K., and Peebles, P.C., 1982, Guidebook to the late Cenozoic geology of the lower York-James Peninsula, Virginia: Williamsburg, Va., College of William and Mary, Department of Geology Guidebook 3, 58 p. Johnson, G.H., Kruse, S.E., Vaughn, A.W., Lucey, J.K., Hobbs, C.H., III, and Powars, D.S., 1998, Postimpact deformation associated with the late Eocene Chesapeake Bay impact structure in southeastern Virginia: Geology, v. 26, no. Obtaining cores and placing monitoring wells in and around the crater would help us understand how this impact crater has affected the regional ground- water resources. As an example, well 58F50 is in quadrangle 58F and is the 50th well in that quadrangle for which the location and other data were recorded by the USGS. Syn-impact deposits present within the disruption boundary and outer rim of the CBIC beneath the lower York-James Peninsula include the seismically defined CBIC megablock beds and the upper Eocene Exmore tsunami-breccia. Geological Society of America Abstracts with Programs, Volume 26, p. 410.. (2004) The Chesapeake Bay Crater: Geology and Geophysics of a Late Eocene Submarine Impact Structure, Springer-Verlag, Berlin, 2004. The distribution of crater-fill materials i n the CBIS is related to the morphology. Back, W., 1966, Hydrochemical facies and ground-water flow patterns in northern part of Atlantic Coastal Plain: U.S. Geological Survey Professional Paper 498-A, 42 p., 1 plate. (Powars and others, 1992; Verteuil and Norris, 1992, 1996) and, therefore, represent the Plum Point Member (upper two-thirds) and Calvert Beach Member of the Calvert Formation. 13), progressively onlapping and truncating older units west to southwest of the crater. In Studies of the Chesapeake Bay Impact Structure - The USGS-NASA Langley Corehole, Hampton, Virginia, and Related Coreholes and Geophysical Surveys: U.S. Geological Survey Professional Paper 1688. The lower Miocene bioclastic sand facies consist of olive to olive-gray to dark-olive-gray, very poorly sorted, very shelly, medium to pebbly, glauconitic and phosphatic quartz sand to shell hash. 12). Lithologies of cores are correlated with borehole geophysical logs to characterize the physical properties of the stratigraphic units and their geophysical signatures. Planetary impact craters are a common surface feature of many planetary bodies, including the Earth, the Moon, Mars, Mercury, Venus, and Jupiter s moons, Ganymede and Callisto. The Chesapeake Bay impact crater (CBIC) was formed when a large comet or meteorite crashed into shallow shelf-depth waters of the western Atlantic Ocean approximately 35 million years ago (Ma). Learn more here. Blocky signatures on the resistivity and gamma logs also reflect the overall thicker bedded character of the Lower Cretaceous deposits compared to the thinner, more gradational curves representing the Aquia strata. ]: Geological Society of America Abstracts with Programs, v. 26, p. 410. Richmond, VA 23228 The finer grained beds encountered in the Exmore corehole contain two thin (4.2- and 4.9-ft) fining-upward sequences. Though we have learned much from the geology of the Chesapeake Bay crater, Dan Mazanek, a near-Earth object (NEO) expert at NASA Langley, explained that there is still much left to learn. Richardson, D.L., 1994, Hydrogeology and analysis of the ground-water-flow system of the Eastern Shore, Virginia: U.S. Geological Survey Water-Supply Paper 2401, 108 p. Riddle, P.C., Vaughn, A.W., Lucey, J.K., Kruse, S.E., Johnson, G.H., and Hobbs, C.H., 1996, Geophysical studies of near-surface deformation associated with the Chesapeake Bay impact structure, southeastern Virginia [abs. These faults are zones of crustal weakness and have the potential for continued slow movement, or sudden larger offsets if reactivated by earthquakes. 6A and B , 7A and B ) of the possibly low permeability Exmore tsunami-breccia and the overlying fine-grained Chickahominy Formation (confining unit) can be readily incorporated into the current ground-water model. A lock () or https:// means youve safely connected to the .gov website. The upper Cenomanian beds (pollen zone IV) contain shallow-shelf to marginal-marine to deltaic-lagoonal deposits. These deposits are considered an Eocene stratigraphic unit because the slump blocks are transported and rapidly emplaced by impact cratering processes that most likely mixed them with some Exmore tsunami-breccia and melt. Differentiation of the Delmarva beds from the Old Church is not always possible and, therefore, the two units are undifferentiated and labeled as Oligocene deposits in plates 3 and 4. 4) and makes differentiation from the Yorktown relatively easy on the resistivity logs. (For more information on the Chesapeake Bay Crater please click on the link below.) C of Mixon, R.B., ed., Geology and paleontology of the Haynesville cores--Northeastern Virginia Coastal Plain: U.S. Geological Survey Professional Paper 1489, p. C1-C12. ), 2009. 5), the gamma and resistivity logs reflect the fining-upward sequences of the middle Miocene Calvert Formation, with the relatively thin basal sands having relatively thin high resistivity- and gamma-log signatures. ]: Geological Society of America Abstracts with Programs, v. 22, p. 57. Syn-impact deposits consist of the upper Eocene Exmore tsunami-breccia and the seismically defined Chesapeake Bay impact crater megablock beds (CBIC megablock beds). The Exmore tsunami-breccia's chaotic seismic signature sharply contrasts with the long, continuous, parallel, high-amplitude reflectors of the overlying Chickahominy Formation strata and is easily recognized. Problems with differentiating the St. Marys from the underlying clayey middle Miocene Calvert Formation were discussed in the last section (including geophysical log signatures). ; Stories of Impact Hear how Soccer Shots has impacted children nationwide. Northeastern, USA | mysite The correlation between cores, well cuttings, and borehole geophysical logs is augmented with seismic-reflection data, and these data are compiled into a lithostratigraphic cross section that illustrates the geological framework of the lower York-James Peninsula and immediate surrounding areas. Inside this preserved limit and inside the crater, the Mattaponi Formation is equivalent to the Exmore tsunami-breccia deposits. The inner basin includes a central uplift surrounded by a series of concentric valleys and ridges. ]: Geological Society of America Abstracts with Programs, v. 26, p. A-152. The structural and stratigraphic features created by the impact have influenced the hydrogeology, ground-water flow system, and water quality of a large part of the Virginia Coastal Plain. In this huge new reservoir, pore spaces are filled with briny water that is 1.5 times saltier than normal seawater. Drilling into the Chesapeake Bay crater . The outer rim of the crater, characterized by a zone dominated by normal-faulted slump blocks, forms a buried, 1,000- to 4,000-foot escarpment. The shelly sandy facies are lithically variable and range from relatively loose, massive, olive-gray, shelly, medium to coarse glauconitic phosphatic quartz sands to the same lithology but with a clay-silt matrix. This was an attempt to account for the possible effect of the crater's outer rim on the ground-water flow system. The challenge is a large-scale effort that will use multi-disciplinary collaborations and a variety of partnerships with other government agencies, international partners, industry, academia, and citizen scientists. The Chowan River Formation (upper Pliocene) has a very limited, sporadic distribution across the southeastern part of the study area and locally is found only in the lower York-James Peninsula. The base of the unit, like most of the marine unconformities found in the Oligocene and Miocene sequence, contains a basal lag deposit of poorly sorted, shelly, woody, pyritic, very fine to very coarse sand, with scattered phosphate pebbles (up to 0.4 in.). Geological Society of America, Abstracts with Programs, Volume 28, No. These profiles were collected in 1986 by Teledyne Exploration and were all processed the same way for the oil companies (see Appendix 3). Seismic resolution of these relatively thin lower Miocene beds of the Calvert Formation is very difficult, and therefore they are grouped together with the underlying Old Church Formation and Delmarva beds as a single seismic stratigraphic unit (pl. The MW4-1 data were used to interpret the lithostratigraphy of well 58D9 (22), at the southern end of cross section E - E ' shown in plate 4. Official websites use .gov In general, the Lower Cretaceous fluvial-deltaic deposits have a much more blocky appearance on their resistivity and gamma logs, reflecting in part the sharp nature of their sand-to-clay contacts. Hoffmeister, Old Dominion University, written commun., 1995). ]: Geological Society of America Abstracts with Programs, v. 25, A-378. About 35 million years ago, a large comet or meteorite slammed into the western Atlantic Ocean on a shallow shelf, creating the Chesapeake Bay impact crater. Gibson R. L., Townsend N. G., Horton J. W. Jr.,, Reimold W. U. Gohn, G.S., Clark, A.C., Queen, D.G., Levine, J.S., McFarland, E.R., and Powars, D.S., 2001, Operational summary for the USGS-NASA Langley corehole, Hampton, Virginia: U.S. Geological Survey Open-File Report 01-87-A, 21 p. Powars, D.S., Bruce, T.S., Bybell, L.M., Cronin, T.M., Edwards, L.E., Frederiksen, N.O., Gohn, G.S., Horton, J.W., Jr., Izett, G.A., Johnson, G.H., Levine, J.S., McFarland, E.R., Poag, C.W., Quick, J.E., Schindler, J.S., Self-Trail, J.M., Smith, M.J., Stamm, R.G., and Weems, R.E., 2001, Preliminary geologic summary for the USGS-NASA Langley corehole, Hampton, Virginia: U.S. Geological Survey Open-File Report 01-87-B, 20 p. Prepared in cooperation with the Hampton Roads Planning District Commission and the NASA Langley Research Center. The complex distribution and truncation of litho-facies, documented by the relatively abundant outcrops and shallow subsurface data of the Yorktown, may be typical of many of the underlying post-impact units for which very little data are available. Differentiation is aided, however, by noting the vertical stacking order of the units. Wylie Poag, U.S. Geological Survey (USGS), identified the Chesapeake Bay Crater, which was formed when an object hit the Atlantic Ocean over 35 million years ago in the late Eocene and is largely responsible for creating the Chesapeake Bay and surrounding area. Poag assembled an international team to investigate its characteristics and consequences. 2B). The York River profile portrays the geometry and structure of the crater's outer rim; the Chesapeake Bay profile shows an east-west cross section of the peak ring and inner basin. Poag, C.W., 1997c, The Chesapeake Bay bolide impact--A convulsive event in Atlantic Coastal Plain evolution, in Seagall, M.P., Colquhoun, D.J., and Siron, D., eds., Evolution of the Atlantic Coastal Plain-Sedimentology, stratigraphy, and hydrogeology: Sedimentary Geology, v. 108, p. 45-90. pp. As ground-water use increases in the Hampton Roads region and public water utilities increasingly tap into brackish-water aquifers as sources of drinking water, additional information about the CBIC will be needed for future management of these ground-water resources. The Chesapeake Bay crater was found by coring and the use of seismic reflection. The structural and stratigraphic features created by the CBIC have dramatically influenced the hydrogeologic framework, ground-water flow system, and regional water quality of the Virginia Coastal Plain. Laczniak, R.J., and Meng, A.A., III, 1988, Ground-water resources of the York-James Peninsula of Virginia: U.S. Geological Survey Water-Resources Investigations Report 88-4059, 178 p. Larson, J.D., 1981, Distribution of saltwater in the Coastal Plain aquifers of Virginia: U.S. Geological Survey Open-File Report 81-1013, 25 p., 2 pls. Selected core intervals were sampled for mineralogic, biostratigraphic, and isotopic analysis. Thickness varies from 7 to 17 ft in wells on Hog Island. All of the seismic sections show that the top of the Exmore tsunami-breccia and the overlying post-impact strata are cut by numerous normal faults. Geological Society of America, Abstracts with Programs, Volume 25, p. A-378. The Meteoritical Society, 2006. Locally, the sands also contain clay-clast conglomerates and lignitic material (finely disseminated to wood chunks to logs). Seismic data from inside the inner basin suggest the undifferentiated Oligocene-Miocene deposits may be as much as 400 ft thick (pl. This implies that the entire Cretaceous section there (about 1,300-ft-thick) is represented only by pollen zone I; however, the older pollen zone K1 may be present. Resistivity logs reflect the very clayey nature of the Marlboro; however, the lowest Nanjemoy beds are often described as a gray clay, making differentiation between these two units difficult. 11, pp. Continued slumping of sediments over the rubble of the crater . 10 Largest Impact Craters on Earth | Science Facts Pliocene and Pleistocene sea-level oscillations created a coast-parallel and river-parallel series of terraces and scarps across the peninsula. Two additional multichannel seismic profiles that help define the CBIC were collected and processed by the USGS in 1982. The deepest unitinthe corehole is the NeoproterozoicLangleyGranite. The high relief of the peak ring on the south side of the crater and the apparent underplating of the peak ring on the north side indicates an angled impact trajectory from the northeast (D.S.
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