Quaternary seismic facies of the atlantic continental rise

High-resolution seismic profiles collected by Parasound and SES-2000 deep profilers during Cruise 26 of the R/V Akademik Sergei Vavilov (2009) along the continental slope base of South America, NW Africa, and West Europe are correlated with the deep-sea drilling boreholes. Lithofacies interpretation of the Quaternary deep-water seismic facies of hemipelagites, bottom current deposits (contourites), and gravitites (turbidites, mud flow deposits) is presented. The data obtained reveal the domination of contourites in the accumulation of continental rise apron under conditions of relatively scarce terrigenous material supply. It is shown that acoustically stratified seismic facies under these conditions commonly reflect interbedding of the terrigenous clay and biogenic calcareous ooze related to the Pleistocene glacial/interglacial cycles.     

Geophysical consequences of planetary-scale impacts into a Mars-like planet

All planetary bodies with old surfaces exhibit planetary-scale impact craters: vast scars caused by the large impacts at the end of Solar System accretion or the late heavy bombardment. Here we investigate the geophysical consequences of planetary-scale impacts into a Mars-like planet, by simulating the events using a smoothed particle hydrodynamics (SPH) model. Our simulations probe impact energies over two orders of magnitude (2 × 10²⁷-6 × 10²⁹ J), impact velocities from the planet’s escape velocity to twice Mars’ orbital velocity (6-50 km/s), and impact angles from head-on to highly oblique (0-75°). The simulation results confirm that for planetary-scale impacts, surface curvature, radial gravity, the large relative size of the impactor to the planet, and the greater penetration of the impactor, contribute to significant differences in the geophysical expression compared to small craters, which can effectively be treated as acting in a half-space. The results show that the excavated crustal cavity size and the total melt production scale similarly for both small and planetary-scale impacts as a function of impact energy. However, in planetary-scale impacts a significant fraction of the melt is sequestered at depth and thus does not contribute to resetting the planetary surface; complete surface resetting is likely only in the most energetic (6 × 10²⁹ J), slow, and head-on impacts simulated. A crater rim is not present for planetary-scale impacts with energies >10²⁹ J and angles ?45°, but rather the ejecta is more uniformly distributed over the planetary surface. Antipodal crustal removal and melting is present for energetic (>10²⁹ J), fast (>6 km/s), and low angle (?45°) impacts. The most massive impactors (with both high impact energy and low velocity) contribute sufficient angular momentum to increase the rotation period of the Mars-sized target to about a day. Impact velocities of >20 km/s result in net mass erosion from the target, for all simulated energies and angles. The hypothesized impact origin of planetary structures may be tested by the presence and distribution of the geochemically-distinct impactor material.     

Tectonics of the Ninety-East Ridge

New multibeam bathymetry data and multichannel seismic profiles over 7 detailed survey sites collected during cruise no. KNOXRR06 of the R/V Rodger Revelle in 2007 fundamentally expanded the concepts about the structure of the sedimentary cover of the Ninety-East Ridge, which were based on the results of previous studies. They allow making a step forward in interpreting the nature of the unconformities and deformations. The deformation pattern of the sedimentary cover suggests three stages of tectonic activity over the ridge during the Paleocene, Eocene, and Late Miocene. As suggested by the high present-day seismicity, the last stage might continue to the present time. In addition, indirect criteria indicate young intraplate volcanism at the last stage. New data is reviewed in the context of two models of the ridge formation. The first model follows a well-known concept of the ridge representing a trace of the Kerguelen hotspot. The second one relates large outflows of basalts to the development of a giant fracture under conditions of global extension, which continued later during the sedimentary cover formation. Additional integrated geological and geophysical studies are required for understanding the nature of this unique feature.     

Performance evaluation of underwater platforms in the context of space exploration

Robotic platforms are essential for future human planetary and lunar exploration as they can operate in more extreme environments with a greater endurance than human explorers. In this era of space exploration, a terrestrial analog that can be used for development of the coordination between manned and robotic vehicles will optimize the scientific return of future missions while concurrently minimizing the downtime of both human explorers and robotic platforms. This work presents the use of underwater exploratory robots - autonomous underwater vehicles (AUV), remotely operated vehicles (ROV), and manned submersibles - as analogues for mixed human-robot exploration of space. Subaqueous settings present diverse challenges for navigation, operation and recovery that require the development of an exploration model of a similar complexity as required for space exploration. To capitalize on the strengths of both robotic and human explorers this work presents lessons learnt with respect to the fields of human-robotic interface (HRI) and operator training. These are then used in the development of mission evaluation tools: (1) a task efficiency index (TEI), (2) performance metrics, and (3) exploration metrics. Although these independent evaluations were useful for specific missions, further refinement will be required to fully evaluate the strengths and capabilities of multiple platforms in a human-robotic exploration campaign in order to take advantage of unforeseen science opportunities in remote settings.     

New Data on the Geology of Osborn Plateau,Indian Ocean

Doklady Earth Sciences - The Osborn Plateau is a large intraplate rise in the eastern part of the Indian Ocean, which has been poorly studied by the geological and geophysical methods. In cruise...     

The Nature and Evolution of the Ninetyeast Ridge: A Key Tectonic and Magmatic Feature of the East Indian Ocean

Geotectonics - The Ninetyeast Ridge is the longest linear intraplate rise in the World Ocean and the main tectonic and magmatic feature in the East Indian Ocean. Ideas about the nature and...     

Stratigraphic Hiatuses in the Sedimentary Cover of the Ninetyeast Ridge

The Ninetyeast Ridge is one of the longest structures in the World Ocean. Owing to the seismostratigraphic analysis, three seismic complexes are distinguished in the sedimentary cover of this ridge, lower subaerial—shallow-water (SC3), transition (SC2), and upper deep-water (SC1), and nine reflectors: 0, 0a, 1, 1a, 2, 3, 4, 5, and F. On the basis of the results of correlation of seismic sections with those of deepwater sites recording the entire period of formation of the sedimentary cover of the Ninetyeast Ridge (Late Cretaceous—Quaternary), several nondepositional hiatuses are distinguished. The following reasons for these hiatuses are proposed. The hiatus in the beginning of the Early Paleocene coincides in time with the general decrease in the World Ocean level and is recorded only within the northern part of the ridge. The first “soft” collision of the Indian and Eurasian plates, as well as Paleocene—Eocene Thermal Maximum (PETM), could have been a reason for the most long-lasting hiatus in the Early—Middle Eocene in the northern and central parts of the Ninetyeast Ridge. The hiatus in the Early Oligocene is also distinguished in these parts of the ridge and is likely associated with underwater erosion. The formation of the Antarctic Circumpolar Current (ACC) and the change in the hydrodynamic regime of the Indian Ocean could have been reasons for the hiatus in the Middle Miocene, which is traced in the sedimentary cover throughout the entire Ninetyeast Ridge.     

Speleothem-based chronology and environmental context of deposits from the Mishin Kamik Cave,NW Bulgaria – A contribution to the archaeological study of the Late Pleistocene human occupation in the Balkans

The Balkan Peninsula represents one of the most important human pathways into and out of Europe during the Pleistocene. Mishin Kamik cave, located in the karst region of Western Stara Planina, has a rich faunal content and shows promising features indicating a human occupation site with the discovery of potential bone artefacts and an intriguing accumulation of bear skulls and bones. Petrographic study and U-series dating of a stalagmite and other calcite deposits in the cave provide an absolute chronological frame for the detrital infillings and their archaeological content and inform the environmental and climatic context of the cave evolution. Most detrital deposits in the cave were probably deposited before Marine Isotope Stage (MIS) 5 and the cave morphology and sedimentary deposits display current morphologies since ~135 ka. Consequently, the palaeontological and archaeological findings are older than ~135 ka. Calcite dated on and under the accumulation of bear skulls and bones suggests deposition during MIS 7. A first depositional contextualization of the bone accumulation does not allow us to discriminate between a natural or anthropogenic origin. The study emphasizes the added value of speleothem studies in archaeological sites and particularly in bringing a well-constrained chronological and environmental framework.