1-20 OF 24 RESULTS FOR

Exmore Breccia

Results shown limited to content with bounding coordinates.
Follow your search
Access your saved searches in your account

Would you like to receive an alert when new items match your search?
×Close Modal
Sort by
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(29)
... (444–1397 m depth) of sedimentary clast breccia and intercalated sedimentary and crystalline megablocks known as Exmore beds, deposited on top of the impactite sequence between 1397 and 1551 m depth. We petrographically investigated the sandy-clayey groundmass-dominated breccia, which resembles...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(22)
... We investigated whole-rock chemical compositions of 318 samples of Exmore breccia (diamicton), impactite (suevite, impact melt rock, polymict lithic impact breccia), and crystalline basement-derived rocks from 444 to 1766 m depth in the International Continental Scientific Drilling Program...
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)
..., and the composition of the particles could have been modified by hydrothermal alteration. Carbon isotope ratios were determined for 18 samples. The results imply a hydrothermal origin for the carbonate veins from the basement-derived core section; carbon-rich sedimentary clasts from the Exmore breccia and suevite...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(30)
... (generally, <10% illite layers). Thin section and scanning electron microscope petrography in the Exmore breccia show evidence for extensive authigenic expandable clay in the matrix and dispersed pyrite lepispheres and fine calcite rhombs. Grain alteration includes feldspar dissolution and albitization...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(07)
..., density, velocity, and thermal properties on the densely sampled cores from the Eyreville borehole in the Chesapeake Bay impact structure, USA. With increasing depth, the lithologies encountered (and porosities) are: postimpact sediments (40%–60%), Exmore breccia and sedimentary blocks (27%–44%), a large...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(31)
... breccias, poorly sorted conglomerate and sandstone, and upward-fining glauconitic sandstone within the Exmore beds followed by parallel laminated sandy siltstone and claystone in the Chickahominy Formation. They all contain clay minerals (mica, smectites, and some serpentine, kaolinite, and chlorite) plus...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(09)
... of the structure. Densities from the Eyreville drill core and modeling indicate a density contrast of ~0.3–0.6 g cm −3 between crystalline basement and the material that fills the inner crater (e.g., Exmore breccia and suevite). This density contrast is somewhat higher than for other impact structures...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(32)
... directly above the crater-filling Exmore breccia. Step 2 is represented by very thin, parallel, silt and clay laminae, which accumulated on a relatively tranquil and stagnant seafloor. This stagnation created a dead zone, which excluded seafloor biota, and it lasted ~3–5 ka. Step 3 is an interval of marine...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(03)
... The Eyreville A and B cores, recovered from the “moat” of the Chesapeake Bay impact structure, provide a thick section of sediment-clast breccias and minor stratified sediments from 1095.74 to 443.90 m. This paper discusses the components of these breccias, presents a geologic column...
Series: GSA Special Papers
Published: 01 January 2009
DOI: 10.1130/2009.2458(25)
... of polymict lithic breccia, suevite, and impact melt rock (1397–1551 m) must have been deposited prior to the arrival of the 950-m-thick resurge and avalanche-delivered beds and blocks within 5–7 min after impact. (3) This short period for transportation and deposition of impactites may suggest...
Journal Article
Journal: Geology
Published: 01 November 2002
Geology (2002) 30 (11): 995-998.
..., pyrite microstructures at the top of the Exmore crater-fill breccia. The porous geometry of the pyrite microstructures indicates that they originally were part of a more extensive pyrite lattice that encompassed a layer of millimeter-scale glass microspherules—fallout melt particles produced...
FIGURES | View All (5)
Series: GSA Special Papers
Published: 01 January 2007
DOI: 10.1130/2008.2437(07)
... The Breccia provides rare opportunities to understand impact events. Widespread, tectonically tilted and eroded ranges exhibit expansive outcrops that are mostly bare owing to desert climate and sparse vegetation. They reveal the base, top, internal character, and stratigraphic context...
FIGURES | View All (21)
Series: GSA Special Papers
Published: 01 January 2007
DOI: 10.1130/2008.2437(06)
... sediments in the annular trough, and (3) a polymict diamicton of allogenic sediment-clast breccia (Exmore beds in the restrictive sense of Gohn et al., 2005 ) that blankets the entire structure and nearby areas. Using the proposed classification of impactites by Stöffler and Grieve (1994 , 2007...
FIGURES | View All (11)
Image
Figure 5. Photomicrographs (plane-polarized light) of thin sections showing...
in > Geology
Published: 01 November 2002
Figure 5. Photomicrographs (plane-polarized light) of thin sections showing intact, but partly dissolved, glass microspherules present in samples of Exmore breccia in Windmill Point corehole (A, C) and Exmore corehole (B).
Image
Figure 3. Stratigraphic column showing sample locations (numbered black rec...
in > Geology
Published: 01 November 2002
sand contain stratigraphically mixed, diagenetically altered, and impact-altered microfossils. B: Split core segment (sample 7) showing slightly undulating contact between dead zone (with horizontal laminae of sand, silt, and clay; upper part of Exmore breccia) and burrowed marine clay containing
Journal Article
Journal: Geology
Published: 01 December 2005
Geology (2005) 33 (12): 925-928.
... a strong carbonate unit to an extremely fluid-like wet tuff. A viable model of the Chesapeake Bay impact must explain three peculiar aspects of the crater: the broad and extremely shallow crater topography, the thick Exmore breccia unit, and the confinement of the major basement deformation...
FIGURES
Journal Article
Journal: Geology
Published: 01 August 2003
Geology (2003) 31 (8): 697-700.
... and disaggregation of slump blocks that are little altered internally ( Powars et al., 2001 ). Crater unit C (the Exmore beds) is a sedimentary-clast breccia that is matrix supported and consists of clasts of late Early Cretaceous to late Eocene age. The matrix sediments are largely marine in origin, as are many...
FIGURES | View All (4)
Series: GSA Special Papers
Published: 29 November 2018
DOI: 10.1130/2018.2537
EISBN: 9780813795379
..., 85-km-wide, peak-ring impact structure in the southern Chesapeake Bay area ( Poag et al., 1994 ). The name of the Exmore unit was changed in that paper to the “Exmore breccia,” using the then-current interpretation that the unit consisted primarily of ejecta. In a concurrent study, Poag and Aubry...
FIGURES | View All (29)
Journal Article
Journal: PALAIOS
Published: 01 June 2003
PALAIOS (2003) 18 (3): 275-285.
... sediment clasts suspended in an unstratified, muddy, sandy matrix that includes sparse shocked basement-rock clasts and shocked quartz ( Powars et al., 2001 , 2002 ). This polymict breccia represents resurge and tsunami deposits and informally is termed the “Exmore beds” after the town closest...
FIGURES | View All (6)