Postimpact alteration of sedimentary breccias in the ICDP-USGS Eyreville A and B cores with comparison to the Cape Charles core, Chesapeake Bay impact structure, Virginia, USA

Larsen, Daniel; Stephens, Elizabeth; Zivkovic, Vladimir B.

doi:10.1130/2009.2458(30)

Cited by 4 publications

(13 citation statements)

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“…Bulk XRD analyses of the gravelly sands in this study, as well as previous studies (Horton et al. 2009b; Larsen et al. 2009), identified the mineral assemblage of quartz, K‐feldspar (microcline), kaolinite, smectite, and mica (muscovite).…”

Section: Discussionsupporting

confidence: 83%

“…Also the amphibolite and cataclastic gneiss show no evidence of shock metamorphism, which suggests an origin from the outer parts of the transient crater. We did not observe any microtektites as described by Larsen et al. (2009).…”

Section: Resultssupporting

confidence: 46%

“…The postimpact alteration of the Eyreville sedimentary breccias has been studied by Larsen et al. (2009), who describe one sample from the upper gravelly sand (1375 m depth) as to include quartz and microcline as well as rock fragments and purported “microtektites.” The feldspars show dissolution, albitization, and replacement by clay minerals; in addition, some quartz grains with syntaxial quartz overgrowths suggest the initiation of quartz cementation, although grains are not yet cemented together (Larsen et al. 2009).…”

Section: Background and Previous Workmentioning

confidence: 99%

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Petrography, mineralogy, and geochemistry of deep gravelly sands in the Eyreville B core, Chesapeake Bay impact structure

Bartošová

Gier

Horton

et al. 2010

Meteoritics &Amp; Planetary Science

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Abstract-The ICDP-USGS Eyreville drill cores in the Chesapeake Bay impact structure reached a total depth of 1766 m and comprise (from the bottom upwards) basement-derived schists and granites ⁄ pegmatites, impact breccias, mostly poorly lithified gravelly sand and crystalline blocks, a granitic slab, sedimentary breccias, and postimpact sediments. The gravelly sand and crystalline block section forms an approximately 26 m thick interval that includes an amphibolite block and boulders of cataclastic gneiss and suevite. Three gravelly sands (basal, middle, and upper) are distinguished within this interval. The gravelly sands are poorly sorted, clast supported, and generally massive, but crude size-sorting and subtle, discontinuous layers occur locally. Quartz and K-feldspar are the main sand-size minerals and smectite and kaolinite are the principal clay minerals. Other mineral grains occur only in accessory amounts and lithic clasts are sparse (only a few vol%). The gravelly sands are silica rich (80 wt% SiO 2 ). Trends with depth include a slight decrease in SiO 2 and slight increase in Fe 2 O 3 . The basal gravelly sand (below the cataclasite boulder) has a lower SiO 2 content, less K-feldspar, and more mica than the higher sands, and it contains more lithic clasts and melt particles that are probably reworked from the underlying suevite. The middle gravelly sand (below the amphibolite block) is finer-grained, contains more abundant clay minerals, and displays more variable chemical compositions than upper gravelly sand (above the block). Our mineralogical and geochemical results suggest that the gravelly sands are avalanche deposits derived probably from the nonmarine Potomac Formation in the lower part of the target sediment layer, in contrast to polymict diamictons higher in the core that have been interpreted as ocean-resurge debris flows, which is in agreement with previous interpretations. The mineralogy and geochemistry of the gravelly sands are typical for a passive continental margin source. There is no discernible mixing with marine sediments (no glauconite or Paleogene marine microfossils noted) during the impact remobilization and redeposition. The unshocked amphibolite block and cataclasite boulder might have originated from the outer parts of the transient crater.

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Section: Discussionsupporting

confidence: 83%

Section: Resultssupporting

confidence: 46%

Section: Background and Previous Workmentioning

confidence: 99%

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Petrography, mineralogy, and geochemistry of deep gravelly sands in the Eyreville B core, Chesapeake Bay impact structure

Bartošová

Gier

Horton

et al. 2010

Meteoritics &Amp; Planetary Science

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“…However, the Eyreville impact melts do not exhibit the same fractured appearance with phyllosilicate-rich veins seen at the Yax-1 site. Furthermore, the evidence from fluid inclusion studies (Vanko, 2009) and phyllosilicate mineralogy (Larsen et al, 2009) suggests that the hydrothermal system at the $85 km diametre Chesapeake Bay structure evidenced in the Eyreville sequence, and even in the Cape Charles drill core from near the central uplift was relatively low temperature compared to the system at the Yax-1 site. Only low temperature alteration has been noted at other (but much smaller) marine impacts such as Kärdla (Kirsimäe et al, 2002) and Lockne (Sturkell et al, 1998).…”

Section: Matrix Phyllosilicate Formation By Precipitationmentioning

confidence: 95%

Petrographic investigation of melt and matrix relationships in Chicxulub crater Yaxcopoil-1 brecciated melt rock and melt rock-bearing suevite (846–885m, units 4 and 5)

Nelson

Newsom

Spilde

et al. 2012

Geochimica et Cosmochimica Acta

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“…The fracturing may have occurred during crater formation. Central uplifts and neighboring fracture zones of terrestrial and martian craters are known to experience hydrothermal circulation consequent of the impact event (Komor et al, 1988;Larson et al, 2009). Stresses undergone by a section as it is thrust to the surface may also leave km-scale folds and faults throughout the central uplift (Fig.…”

Section: Basic Morphology Of Lmbmentioning

confidence: 99%

Layered MegaBlocks in the central uplifts of impact craters

Caudill¹,

Tornabene²,

McEwen³

et al. 2012

Icarus

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Postimpact alteration of sedimentary breccias in the ICDP-USGS Eyreville A and B cores with comparison to the Cape Charles core, Chesapeake Bay impact structure, Virginia, USA

Cited by 4 publications

References 0 publications

Petrography, mineralogy, and geochemistry of deep gravelly sands in the Eyreville B core, Chesapeake Bay impact structure

Petrography, mineralogy, and geochemistry of deep gravelly sands in the Eyreville B core, Chesapeake Bay impact structure

Petrographic investigation of melt and matrix relationships in Chicxulub crater Yaxcopoil-1 brecciated melt rock and melt rock-bearing suevite (846–885m, units 4 and 5)

Layered MegaBlocks in the central uplifts of impact craters

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