The anatomy of a buried complex impact structure: The Mjølnir Structure, Barents Sea

Tsikalas, Filippos; Guðlaugsson, Steinar Þór; Faleide, Jan Inge

doi:10.1029/97jb03389

Cited by 44 publications

(69 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Collapse of this cavity starts at its base and causes a flow of water and rock debris toward the crater center (e.g., Shuvalov 2002). These processes at marinetarget craters may explain the lack of a raised crater rim at the Mjølnir (Tsikalas et al 1998a(Tsikalas et al , 1998bTsikalas and Faleide 2004), Lockne (Sturkell and Lindström 2004), Chesapeake Bay (Poag et al 1994(Poag et al , 2004, and Chicxulub (e.g., Morgan et al 2002a) craters, and the beveled crater rim at Montagnais crater (Jansa et al 1989;Jansa 1993) (cf. Figs.…”

Section: Post-impact Infillingmentioning

confidence: 99%

“…The integrated geophysical modeling at Mjølnir demonstrates a close correspondence of geophysical anomalies to the radially varying distribution of structural and morphological units, and to the physical properties distribution. Specifically, the impact resulted in an extensive, 850-1400 km 3 (Tsikalas et al 1998b), seismically disturbed volume at the impact site (Fig. 10), which exhibits relatively increased porosities and decreased densities and velocities in the highly fractured, brecciated, and collapsed crater periphery.…”

Section: Changes In Geophysical Signature Responsementioning

confidence: 99%

“…6), the depth-conversion was based on the velocity-depth function of Tsikalas et al (1998b). A welllog derived porosity-depth relationship for siliciclastic sediments (Ø o ∼55%; c 0.42 km− 1 ) developed for the southwestern Barents Sea (Tsikalas 1992) was used to decompact the post-impact sequences.…”

Section: Reconstruction Of the Original Crater Reliefmentioning

confidence: 99%

See 2 more Smart Citations

Post‐impact structural crater modification due to sediment loading: An overlooked process

Tsikalas

Faleide

2007

Meteorit & Planetary Scien

Self Cite

View full text Add to dashboard Cite

Abstract-Post-impact crater morphology and structure modifications due to sediment loading are analyzed in detail and exemplified in five well-preserved impact craters: Mjølnir, Chesapeake Bay, Chicxulub, Montagnais, and Bosumtwi. The analysis demonstrates that the geometry and the structural and stratigraphic relations of post-impact strata provide information about the amplitude, the spatial distribution, and the mode of post-impact deformation. Reconstruction of the original morphology and structure for the Mjølnir, Chicxulub, and Bosumtwi craters demonstrates the long-term subsidence and differential compaction that takes place between the crater and the outside platform region, and laterally within the crater structure. At Mjølnir, the central high developed as a prominent feature during post-impact burial, the height of the peak ring was enhanced, and the cumulative throw on the rim faults was increased. The original Chicxulub crater exhibited considerably less prominent peakring and inner-ring/crater-rim features than the present crater. The original relief of the peak ring was on the order of 420-570 m (currently 535-575 m); the relief on the inner ring/crater rim was 300-450 m (currently ∼700 m). The original Bosumtwi crater exhibited a central uplift/high whose structural relief increased during burial (current height 101-110 m, in contrast to the original height of 85-110 m), whereas the surrounding western part of the annular trough was subdued more that the eastern part, exhibiting original depths of 43-68 m (currently 46 m) and 49-55 m (currently 50 m), respectively. Furthermore, a quantitative model for the porosity change caused by the Chesapeake Bay impact was developed utilizing the modeled density distribution. The model shows that, compared with the surrounding platform, the porosity increased immediately after impact up to 8.5% in the collapsed and brecciated crater center (currently +6% due to post-impact compaction). In contrast, porosity decreased by 2-3% (currently −3 to −4.5% due to post-impact compaction) in the peak-ring region. The lateral variations in porosity at Chesapeake Bay crater are compatible with similar porosity variations at Mjølnir crater, and are considered to be responsible for the moderate Chesapeake Bay gravity signature (annular low of −8 mGal instead of −15 mGal). The analysis shows that the reconstructions and the long-term alterations due to post-impact burial are closely related to the impact-disturbed target-rock volume and a brecciated region of laterally varying thickness and depthvarying physical properties. The study further shows that several crater morphological and structural parameters are prone to post-impact burial modification and are either exaggerated or subdued during post-impact burial. Preliminary correction factors are established based on the integrated reconstruction and post-impact deformation analysis. The crater morphological and structural parameters, corrected from post-impact loading and modification effects, can be used to better const...

show abstract

Section: Post-impact Infillingmentioning

confidence: 99%

Section: Changes In Geophysical Signature Responsementioning

confidence: 99%

See 1 more Smart Citation

Post‐impact structural crater modification due to sediment loading: An overlooked process

Tsikalas

Faleide

2007

Meteorit & Planetary Scien

Self Cite

View full text Add to dashboard Cite

show abstract

“…The relative height of the stratigraphic uplift with respect to the pre-impact surface also appears variable and not directly correlated with crater size. For example, interpreted profiles across the Manson (Anderson et al 1994), Mjølnir (Tsikalas et al 1998), and Puchezh-Katunki (Fig. 3b) craters place the top of the uplift close to the pre-impact surface, while at both Ries (Fig.…”

Section: Stratigraphic Upliftmentioning

confidence: 99%

Chicxulub central crater structure: Initial results from physical property measurements and combined velocity and gravity modeling

Vermeesch

Morgan

2004

Meteorit & Planetary Scien

View full text Add to dashboard Cite

Abstract-The Chicxulub crater in Mexico is a nearly pristine example of a large impact crater. Its slow burial has left the central impact basin intact, within which there is an apparently uneroded topographic peak ring. Its burial, however, means that we must rely on drill holes and geophysical data to interpret the crater form. Interpretations of crater structures using geophysical data are often guided by numerical modeling and observations at other large terrestrial craters. However, such endeavors are hindered by uncertainties in current numerical models and the lack of any obvious progressive change in structure with increasing crater size. For this reason, proposed structural models across Chicxulub remain divergent, particularly within the central crater region, where the deepest well is only ~1.6 km deep. The shape and precise location of the stratigraphic uplift are disputed. The spatial extent and distribution of the allogenic impact breccias and melt rocks remain unknown, as do the lithological nature of the peak ring and the mechanism for its formation.The objective of our research is to provide a well-constrained 3D structural and lithological model across the central region of the Chicxulub crater that is consistent with combined geophysical data sets and drill core samples. With this in mind, we present initial physical property measurements made on 18 core samples from the Yaxcopoil-1 (Yax-1) drill hole between 400 and 1500 m deep and present a new density model that is in agreement with both the 3D velocity and gravity data. Future collation of petrophysical and geochemical data from Yax-1 core, as well as further seismic surveys and drilling, will allow us to calibrate our geophysical models-assigning a suite of physical properties to each lithology. An accurate 3D model of Chicxulub is critical to our understanding of large craters and to the constraining of the environmental effects of this impact.

show abstract

“…Potential causes would include a tsunami produced by a marine landslide (22) or deepwater bolide impact (23), which rarely leave superficial geological evidence (24). Hurricanes and volcanic eruptions are probably too localized to cause widespread extinction (25,26), but loss of habitat following abrupt climate change might have a regional impact.…”

mentioning

confidence: 99%

Nonequilibrium Diversity Dynamics of the Lesser Antillean Avifauna

Ricklefs

Bermingham

2001

Science

123

102

View full text Add to dashboard Cite

MacArthur and Wilson's model of island diversity predicts an increase in the number of species until colonization and extinction are balanced at a long-term steady state. We appraise this model on an evolutionary time scale by molecular phylogenetic analysis of the colonization of the Lesser Antilles by small land birds. The pattern of accumulation of species with time, estimated by genetic divergence between island and source lineages, rejects a homogeneous model of colonization and extinction. Rather, our results suggest an abrupt, roughly 10-fold increase in colonization rate or a 90% mass extinction event 0.55 to 0.75 million years ago.MacArthur and Wilson's (1) equilibrium theory of biogeography explains the number of species on islands as representing a balance between colonization and extinction. Accordingly, the biota of an island reaches a steady state at which the appearance of new species equals the disappearance of residents. Lack (2) argued instead that colonization was not limiting and that the ecological space on islands was filled with established populations that resisted replacement by new colonists. Both theories hold that the number of species on an island should be stable over long periods, but they differ with respect to the rate of accumulation of species and the prediction of species turnover.

show abstract

The anatomy of a buried complex impact structure: The Mjølnir Structure, Barents Sea

Cited by 44 publications

References 50 publications

Post‐impact structural crater modification due to sediment loading: An overlooked process

Post‐impact structural crater modification due to sediment loading: An overlooked process

Chicxulub central crater structure: Initial results from physical property measurements and combined velocity and gravity modeling

Nonequilibrium Diversity Dynamics of the Lesser Antillean Avifauna

Contact Info

Product

Resources

About