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Cagayan de Oro, Philippines

Schmieder M.,Philamlife Village | Buchner E.,Neu-Ulm University | Buchner E.,University of Stuttgart | Salameh E.,University of Jordan | Khoury H.,University of Jordan
Arabian Journal of Geosciences | Year: 2015

In their recent article, Abed et al. (Arab J Geosci DOI: 10.1007/s12517-014-1427-6, 2014) critically address the impact nature of the ∼6 km Jebel Waqf as Suwwan impact structure in eastern Jordan. We here comment on several statements the authors make in their study. Altogether, the presence of a very typical impact crater structure and morphology, well-developed shatter cones in situ, and planar fractures in combination with feather features and transmission electron microscopy (TEM)-verified planar deformation features (PDF) in quartz collectively fulfills several shock metamorphic criteria that convincingly characterize the Jebel Waqf as Suwwan structure as a complex meteorite impact structure well accessible for geologic study. © 2014, Saudi Society for Geosciences. Source


Buchner E.,Neu-Ulm University | Buchner E.,University of Stuttgart | Schmieder M.,Philamlife Village
Icarus | Year: 2015

The ~24. km Nördlinger Ries and the ~3.8. km Steinheim Basin in southern Germany are thought to represent a ~14.8. Ma old impact crater doublet. The complex craters of the Steinheim Basin with its crater fill deposits and the Nördlinger Ries and its voluminous impact ejecta blanket are still widely preserved. Although located in an environmental setting that presumably underwent the same erosional history as the Ries crater, field geologic studies suggest that no proximal or distal ejecta of the Steinheim impact event are presently preserved. Generally, the lack of the ejecta blanket around the crater could be explained either by intense erosion, the scarcity of outcrops, or it never formed. In contrast to the lack of ejecta, fluvial and lacustrine Middle Miocene sediments deposited prior to, synchronous with, and shortly after the impact are preserved in many places in the surroundings of to the Steinheim Basin.On low-density asteroids or planets with highly porous target rocks (≥30-40% effective porosity), impact structures can form without significant ejecta outside the craters due to the compaction of porosity and a concordant drastic reduction of the ejecta velocity. In the Steinheim area, the target rocks comprised loose, porous Miocene sands, Upper Jurassic limestones and Middle Jurassic porous sand- and claystones. The average porosity of the entire sedimentary target suite may have reached 20-30% or even higher values assuming the existence of open karst cavities in the Upper Jurassic carbonates. Compaction of the porous target rocks, resulting in the reduction of ejected material, in combination with erosion could explain the apparent lack of impact ejecta in the wider periphery of the Steinheim impact structure. The Steinheim Basin represents the first proposed terrestrial example of an impact crater characterized by porosity-related ejecta suppression, and it is suggested that other sediment-hosted impact structures on Earth might exhibit analogous excavation-process characteristics. © 2014 Elsevier Inc.. Source


BUCHNER E.,Ulm University of Applied Sciences | BUCHNER E.,University of Stuttgart | KROCHERT J.,Cdm Smith | SCHMIEDER M.,Philamlife Village
Geological Magazine | Year: 2015

Various uplift markers suggest asymmetrical uplift of Tenerife Island, with stable conditions in the north but significant uplift of up to 45 m in the south over the past ~42 ka. Fossil shells in beach deposits uplifted by 7.5–9 m were 14C-dated at a Holocene age of 2460±35 bp (1σ). This confirms earlier results and documents very young, and probably still ongoing, uplift of southern Tenerife potentially caused by ascending magma. This underlines that southern Tenerife is probably undergoing a further cycle of volcanic activity that started ~95 ka ago. Copyright © Cambridge University Press 2015 Source

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