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Exmore Formation

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Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(03)
... and descriptive lithologic framework for them, and formalizes the Exmore Formation. From 1095.74 to ~867 m, the cores consist of nonmarine sediment boulders and sand (rare blocks up to 15.3 m intersected diameter). A sharp contact in both cores at ~867 m marks the lowest clayey, silty, glauconitic quartz sand...
Series: GSA Special Papers
Published: 01 September 2010
DOI: 10.1130/2010.2465(19)
... lower part (nonmarine Cretaceous Potomac Formation), but just inside the boundary with respect to its upper part (Exmore Formation and a succession of upper Eocene to Pleistocene postimpact deposits). The site of the U.S. Geological Survey–National Aeronautics and Space Administration Langley core, 6.4...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(30)
... In this study, we extend the knowledge of postimpact alteration processes through an investigation of mineralogy and petrology of 24 samples from the Exmore Formation and sedimentary megablock intervals in the Eyreville borehole within the Chesa-peake Bay impact structure and comparisons...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(31)
... Core descriptions, thin-section analyses, and X-ray powder diffraction analyses of whole-rock samples and clay-sized fractions were employed to interpret the sedimentology and mineralogy of synimpact Exmore beds and the overlying Chickahominy Formation. This study attempts to explain the origin...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(29)
... the collapsing ejecta plume was terminated by the time of deposition of the 458 m material. This raises questions about the positioning of the exact upper contact of Exmore breccia to post-Exmore sediment (Chickahominy Formation), which is currently placed at 444 m depth and which possibly should be revised...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(35)
... the Exmore Formation, suggesting long-term reworking of impact debris within the Chesapeake Bay impact structure. (2) Subsequently, an increase in kaolinite content suggests erosion from soils developed during late Eocene warm and humid climate in agreement with data derived from other Atlantic sites...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(25)
... of shock-deformed debris and melt fragments also occur throughout the Exmore beds. Shard-enriched intervals in the upper Exmore beds indicate that some material interpreted to be part of the hot ejecta plume was incorporated and dispersed into the upper resurge deposits. This suggests that collapse...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(21)
... This paper documents an attempt to detect a meteoritic component in both wash-back (resurge) crater-fill breccia (the so-called Exmore breccia) and in suevites from the Eyreville core hole, which was drilled several kilometers from the center of the 85-km-diameter Chesapeake Bay impact...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(18)
..., recrystallized silica melt, melt with microlites, and dark-brown melt, have distinct chemical compositions. Mixing calculations of the proportions of rocks involved in the formation of various polymict impactites and melt particles were carried out using the Harmonic least-squares MiXing (HMX) calculation...
Journal Article
Journal: Geology
Published: 01 November 2002
Geology (2002) 30 (11): 995-998.
... of the transition from synimpact fallout deposition (in the upper part of the Exmore breccia) to postimpact marine clay deposition (base of the Chickahominy Formation). The shift from synimpact to postimpact deposits is abrupt, and is marked by a 0.3–4.6 cm fallout layer; the unusually preserved contents...
FIGURES | View All (5)
Series: GSA Special Papers
Published: 01 January 2007
DOI: 10.1130/2008.2437(06)
... amounts of reworked Exmore sediments, as indicated by reworked microfossils, during deposition of the Chickahominy Formation and younger Tertiary units ( Edwards and Powars, 2003 ; Edwards et al., 2004 ). In summary, the lower diamicton member of the Exmore beds consists of mixed-age sediment clasts...
FIGURES | View All (11)
Image
Dinoflagellate cysts from the Chesapeake Bay impact structure. Depths are i...
in > Palynology
Published: 01 June 2012
breakage near the apical archeopyle; ventral view? of upper surface; R6467 AI Eyreville A, 471.35 m depth, Exmore Formation; laboratory processing included oxidation/alkali treatment. Figures 2, 3. Enneadocysta sp. fragment with irregularly curled process; orientation uncertain, high and low focus levels
Journal Article
Published: 01 May 2011
Journal of Sedimentary Research (2011) 81 (5): 348-354.
.... , and Sandbakken , P.T. , 2003 , The clay mineralogy of sediments related to the marine Mjølnir impact Crater : Meteoritics and Planetary Science , v. 38 , p. 1437 – 1450 . Ferrell , R.E. , Jr. , and Dypvik , H. , 2009 , The mineralogy of the Exmore beds—Chickahominy Formation boundary...
FIGURES | View All (6)
Image
FIGURE 5 —Altered and unaltered dinocysts and pollen. Scale bar is 50 micro...
in > PALAIOS
Published: 01 June 2003
) Dracodinium varielongitudum (Williams and Downie) Costa and Downie, R6110 DG, Exmore beds, USGS-NASA Langley core, Hampton, Virginia, ventral view of ventral surface. Note star-burst scars where processes once were. (D) Unaltered bisaccate pollen grain from the Pliocene, R6110 C, Yorktown Formation, USGS
Series: GSA Special Papers
Published: 29 November 2018
DOI: 10.1130/2018.2537
EISBN: 9780813795379
... Norway) impact structures. Plate A1. Dinocysts from clasts and matrix of the Exmore Formation in the Bayside core. The 50 µm scale bar applies to all images, except as noted. Laboratory “R” numbers are listed. (A–C) R6190BF; early Eocene; clay clast from the upper diamicton member...
FIGURES | View All (29)
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FIGURE 4 —Altered and unaltered material. Scale bar is 50 micrometers. (A) ...
in > PALAIOS
Published: 01 June 2003
, Exmore beds, USGS-NASA Langley core, Hampton, Virginia, high focus. Arrow points to a rounded edge where the specimen was broken and re-sealed. (M) Turbiosphaera sp., R6110 AR, Chickahominy Formation, USGS-NASA Langley core, Hampton, Virginia, dorso-left-lateral view, mid-focus; reworked twice, once
Series: GSA Field Guide
Published: 01 January 2015
DOI: 10.1130/2015.0040(07)
EISBN: 9780813756400
..., 1999 ; Powars et al., 2015 ) but is not covered in this field trip, although a possibly equivalent unit is exposed above the classic Miocene section in the Calvert Cliffs. Units such as the upper Eocene Exmore and Chickahominy Formations, and the informal Oligocene Delmarva beds and Drummond Corner...
FIGURES | View All (35)
Image
FIGURE 3 —Unaffected material and welded clumps from the USGS-NASA Langley ...
in > PALAIOS
Published: 01 June 2003
FIGURE 3 —Unaffected material and welded clumps from the USGS-NASA Langley core. (A) Typical strew-mount microscope slide, post-impact, Chickahominy Formation, no clumps, shown normal size. (B) Microscope slide from the sediment matrix from the Exmore beds with visible clumps, shown normal size. (C
Journal Article
Journal: Palynology
Published: 01 June 2012
Palynology (2012) 36 (Suppl_1): 80-95.
... breakage near the apical archeopyle; ventral view? of upper surface; R6467 AI Eyreville A, 471.35 m depth, Exmore Formation; laboratory processing included oxidation/alkali treatment. Figures 2, 3. Enneadocysta sp. fragment with irregularly curled process; orientation uncertain, high and low focus levels...
FIGURES | View All (4)
Image
Figure 3. Stratigraphic column showing sample locations (numbered black rec...
in > Geology
Published: 01 November 2002
marine clay (Chickahominy Formation) in NASA Langley core. A: Split core segment (sample 5) in dead zone just above fallout layer shows submillimeter-scale, horizontal, parallel laminae of clay, silt, and sand, with submillimeter lenses of sand. Laminae and lenses of fine to very fine, white, micaceous