Computer simulations of large asteroid impacts into oceanic and continental sites--preliminary results on atmospheric, cratering and ejecta dynamics

Roddy, D. J.; Schuster, S.; Rosenblatt, M.; Grant, Lisa B.; Hassig, P. J.; Kreyenhagen, K. N.

doi:10.1016/0734-743x(87)90068-6

Cited by 77 publications

(33 citation statements)

References 10 publications

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“…For certain relations between impactor diameter and target water depth, the shallow excavation flow generates a concentric shape of the transient crater (terminology adopted from Quaide and Oberbeck 1968). This has been reproduced in numerical simulations (e.g., Roddy et al 1987;Shuvalov and Artemieva 2001;Artemieva and Shuvalov 2002;Ormö et al 2002). The shallow excavation flow along the seafloor can generate a permanent concentricity of the crater by stripping not only the water from the surroundings of the nested, central crater depression but the weaker layers of the seafloor as well (e.g., the Lockne crater, Sweden; Lindström et al 1996b;Ormö and Lindström 2000).…”

Section: The Formation and Preservation Of Marine-target Craters On Ementioning

confidence: 95%

Marine‐target craters on Mars? An assessment study

Ormö

Dohm

Ferris

et al. 2004

Meteorit & Planetary Scien

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Marine-target craters on Mars? An assessment studyAbstract-Observations of impact craters on Earth show that a water column at the target strongly influences lithology and morphology of the resultant crater. The degree of influence varies with the target water depth and impactor diameter. Morphological features detectable in satellite imagery include a concentric shape with an inner crater inset within a shallower outer crater, which is cut by gullies excavated by the resurge of water. In this study, we show that if oceans, large seas, and lakes existed on Mars for periods of time, marine-target craters must have formed. We make an assessment of the minimum and maximum amounts of such craters based on published data on water depths, extent, and duration of putative oceans within "contacts 1 and 2," cratering rate during the different oceanic phases, and computer modeling of minimum impactor diameters required to form longlasting craters in the seafloor of the oceans. We also discuss the influence of erosion and sedimentation on the preservation and exposure of the craters.

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Section: The Formation and Preservation Of Marine-target Craters On Ementioning

confidence: 95%

Marine‐target craters on Mars? An assessment study

Ormö

Dohm

Ferris

et al. 2004

Meteorit & Planetary Scien

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“…At this time, the transient cavity is near to completion (Roddy et al 1987), but the ejection process and the expansion of the plume is not finished yet. For reasons discussed below, the middle suevite is most likely related to a later stage of the development of the ejecta plume.…”

Section: Emplacement Of the Suevitementioning

confidence: 99%

The suevite of drill hole Yucatàn 6 in the Chicxulub impact crater

Claeys

Heuschkel²,

Lounejeva

et al. 2003

Meteorit & Planetary Scien

110

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The suevite of drill hole Yucatàn 6 in the Chicxulub impact craterPhilippe CLAEYS, 1* Sabine HEUSCHKEL, 2 Elena LOUNEJEVA-BATURINA, 3 Gerardo SANCHEZ-RUBIO, 3 Abstract-The suevite breccia of the Chicxulub impact crater, Yucatàn, Mexico, is more variable and complex in terms of composition and stratigraphy than suevites observed at other craters. Detailed studies (microscope, electron microprobe, SEM, XRF) have been carried out on a noncontinuous set of samples from the drill hole Yucatàn 6 (Y6) located 50 km SW from the center of the impact structure. Three subunits can be distinguished in the suevite: the upper unit is a fine-grained carbonate-rich suevite breccia with few shocked basement clasts, mostly altered melt fragments, and formerly melted carbonate material; the middle suevite is a coarse-grained suevite with shocked basement clasts and altered silicate melt fragments; the lower suevite unit is composed of shocked basement and melt fragments and large evaporite clasts. The matrix of the suevite is not clastic but recrystallized and composed mainly of feldspar and pyroxene. The composition of the upper members of the suevite is dominated by the sedimentary cover of the Yucatàn target rock. With depth in well Y6, the amount of carbonate decreases and the proportion of evaporite and silicate basement rocks increases significantly. Even at the thin section scale, melt phases of different chemistry can be identified, showing that no widespread homogenization of the melt took place. The melt compositions also reflect the heterogeneity of the deep Yucatàn basement. Calcite with characteristic feathery texture indicates the existence of formerly pure carbonate melt. The proportion of carbonate to evaporite clasts is less than 5:1, except in the lower suevite where large evaporite clasts are present. This proportion constrains the amount of CO 2 and SO X released by the impact event.

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“…The Exmore breccia is a complex deposit, formed by several unusual, interactive, and nearly instantaneous sedimentary processes. Drawing on previous field studies, experiments, and models (e.g., Oberbeck, 1975;Roddy et al, 1977Roddy et al, , 1987Melosh, 1989), I infer the following general steps in breccia formation (Fig. 17).…”

Section: New Ground-water Reservoir and Sealmentioning

confidence: 99%

The Chesapeake Bay bolide impact: a convulsive event in Atlantic Coastal Plain evolution

Poag

1997

Sedimentary Geology

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Until recently, Cenozoic evolution of the Atlantic Coastal Plain has been viewed as a subcyclical continuum of deposition and erosion. Marine transgressions alternated with regressions on a slowly subsiding passive continental margin, their orderly succession modified mainly by isostatic adjustments, occasional Appalachian tectonism, and paleoclimatic change. This passive scenario was dramatically transformed in the late Eocene, however, by a bolide impact on the inner continental shelf. The resultant crater is now buried 400-500 m beneath lower Chesapeake Bay, its surrounding peninsulas, and the continental shelf east of Delmarva Peninsula. This convulsive event, and the giant tsunami it engendered, fundamentally changed the regional geological framework and depositional regime of the Virginia Coastal Plain, and produced the following principal consequences. (1) The impact excavated a roughly circular crater, twice the size of Rhode Island (-6400 km2) and nearly as deep as the Grand Canyon (-1.3 km deep). (2) The excavation truncated all existing ground-water aquifers in the target area by gouging -4300 km3 of rock from the upper lithosphere, including Proterozoic and Paleozoic crystalline basement rocks and Middle Jurassic to upper Eocene sedimentary rocks. (3) Synimpact depositional processes, including ejecta fallback, massive crater-wall failure, water-column collapse, and tsunami backwash, filled the crater with a porous breccia lens, 600-1200 m thick, at a phenomenal rate of -1200 m/hr. The breccia lens replaced the truncated ground-water aquifers with a single 4300 km3 reservoir, characterized by ground water -1.5 times saltier than normal sea water (chlorinities as high as 25,700 mg/l). (4) A structural and topographic low, created by differential subsidence of the compacting breccia, persisted over the crater at least through the Pleistocene. In the depression are preserved postimpact marine lithofacies and biofacies (upper Eocene, lower Oligocene, lower Miocene) not known elsewhere in the Virginia Coastal Plain. (5) Long-term differential compaction and subsidence of the breccia lens spawned extensive fault systems in the postimpact strata. Many of these faults appear to reach the bay floor, and may be potential hazards for motion-sensitive structures in population centers around Chesapeake Bay. Near-surface fracturing and faulting generated by the impact shock may extend as far as 90 km from the crater rim. (6) Having never completely filled with postimpact sediments. the sea-floor depression over the crater appears to have predetermined the location of Chesapeake Bay. (7) As large impact craters are principal sources for some of the world's precious metals, it is reasonable to expect that metal-enriched sills, dikes, and melt sheets are present in the inner basin of the crater.In addition to these specific consequences, the crater and the convulsive event that produced it, have widespread implications for traditional interpretations of certain structural and depositional features of the Atla...

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Computer simulations of large asteroid impacts into oceanic and continental sites--preliminary results on atmospheric, cratering and ejecta dynamics

Cited by 77 publications

References 10 publications

Marine‐target craters on Mars? An assessment study

Marine‐target craters on Mars? An assessment study

The suevite of drill hole Yucatàn 6 in the Chicxulub impact crater

The Chesapeake Bay bolide impact: a convulsive event in Atlantic Coastal Plain evolution

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