Polished slickensides preserved in the Obir Caves (Austria) close to the Periadriatic Fault System

2020 ◽  
Author(s):  
Stefanie Koppensteiner ◽  
Harald Bauer ◽  
Lukas Plan ◽  
Bernhard Grasemann
Keyword(s):  
Spatial Orientation ◽  
Host Rock ◽  
Fault System ◽  
Rock Fragments ◽  
Seismic Slip ◽  
Slip Surfaces ◽  
Carbonate Host Rock ◽  
Thin Section Analysis ◽  
Section Analysis

<p>We studied polished slickensides, which are perfectly preserved in the Obir Caves (Northern Karavanke Mountains, Austria) situated in the Middle Triassic Wetterstein limestone of the Hochobir massif. The investigated area is located close to the seismogenic ESE-trending Periadriatic Fault System, which is the border between the Eastern and Southern Alps. The polished slickensides observed on a block between two major left-lateral NE-SW trending slickensides record a range of polishing from none to highly-reflective fault surfaces. A classification of the different polishing grades of the fault surfaces inside the cave compared with their spatial orientation shows that there is no relationship between the degree of polishing and fault orientation. Associated cataclastically deformed brittle fault zones and partly polished slickensides at the cave entrance and on the Eastern slope of the Hochobir massif where the fault zone localizes in shattered dolomitic rocks, show similar kinematics and spatial orientation to the faults inside the Obir Caves.</p><p>Thin section analysis identified the smooth fault mirror surfaces as principal slip surfaces. Cataclastic grains are truncated along the principal slip surfaces and along secondary Riedel faults. Five different stages of cataclastic deformation can be distinguished: I) Undeformed carbonate host rock. II) Isolated fractures in the host rock with injected ultracataclastic material. III) Dilation cataclasites containing jigsaw breccia. IV) Ultracataclasite with angular-to-rounded host rock fragments and jigsaw breccia. V) Ultracataclasite with isolated clasts and truncated grains close to the mirror surfaces.</p><p>The microstructures including polished slickensides, injected cataclasites and truncated grains along principal slip surfaces as well as the geological position close to the seismogenic Periadriatic Fault System suggest that the investigated fault surfaces in the Obir Caves formed during seismic slip.</p>

scholarly journals Physical weathering of carbonate host-rock by precipitation of soluble salts in caves: A case study in El Orón-Arco Cave (Region of Murcia, SE Spain)

2019 ◽  
Vol 521 ◽  
pp. 1-11 ◽  
Author(s):  
Fernando Gázquez ◽  
José-María Calaforra ◽  
Nicholas P. Evans ◽  
Alexandra V. Turchyn ◽  
Fernando Rull ◽  
...  
Keyword(s):  
Host Rock ◽  
Soluble Salts ◽  
Se Spain ◽  
Physical Weathering ◽  
Carbonate Host Rock

Details of Thin Section Analysis of Pottery Fabrics

1987 ◽  
Vol 53 (S3) ◽  
pp. 53-59
Author(s):  
Carol Allen
Keyword(s):  
Thin Section ◽  
Clay Matrix ◽  
Thin Section Analysis ◽  
Maximum Measurement ◽  
Section Analysis

Terms usedGrog relates to clay inclusions within the pottery which appear as discrete pieces of varying sizes. Usually such entities are assumed to be crushed parts of pre-existing pots.Sizes of quartz, grog, shell or other inclusions referred to in the analysis concern measurements taken on the longest axis of the grain or piece. In each case the maximum measurement stated is the longest observed in that particular section, and does not infer that other grains in the sample were all of this size, unless stated.Percentages of materials shown as included in the clay matrix are estimates expressed by area using comparison charts (Terry and Chilingar 1955, and Flugel 1982, 247-257).

Geomorphic evidence for active, co-seismic slip along a low-angle normal fault: Panamint Valley, California

2020 ◽  
Author(s):  
Eric Kirby ◽  
Israporn (Grace) Sethanant ◽  
John Gosse ◽  
Eric McDonald ◽  
J Doug Walker
Keyword(s):  
Seismic Hazard ◽  
Normal Fault ◽  
Basin And Range ◽  
Detachment Fault ◽  
Airborne Lidar ◽  
Fault System ◽  
Seismic Slip ◽  
The Past ◽  
Detachment Faults ◽  
Fault Scarps

<p>The mechanical feasibility of co-seismic displacement along low-angle normal fault systems remains an outstanding problem in tectonics.  In the southwestern Basin and Range of North America, large magnitude extension during Miocene – Pliocene time was accommodated along a regionally extensive system of low-angle detachment faults.  Whether these faults remain active today and, if so, whether they rupture during large earthquakes are questions central to understanding the geodynamics of distributed lithospheric deformation and associated seismic hazard.  Here we evaluate the geometric and kinematic relationships of fault scarps developed in Pleistocene – Holocene alluvial and lacustrine deposits with low-angle detachment faults observed along the western flank of the Panamint Range, in eastern California.  We combine analysis of high-resolution topography generated from airborne LiDAR and photogrammetry with a detailed chronology of alluvial fan surfaces and a calibrated soil chronosequence to characterize the recent activity of the fault system.  The range-front fault system is coincident with a low-angle (15-20°), curviplanar detachment fault that is linked to strike-slip faults at its southern and northern ends.  Fanglomerate deposits in the hanging wall of the detachment are juxtaposed with brecciated bedrock in the footwall across a narrow fault surface marked by clay-rich gouge.  Isochron burial dating of the fanglomerate using the <sup>26</sup>Al and <sup>10</sup>Be requires displacement in the past ~800 ka.  The degree of soil development in younger alluvial deposits in direct fault contact with the footwall block suggest displacement along the main detachment in the past as ~80-100 ka.  The geometry of recent fault scarps in Holocene alluvium mimic range-scale variations in strike of the curviplanar detachment fault, suggesting that scarps merge with the detachment at depth.  Moreover, fault kinematics inferred from displaced debris-flow levees and from fault striae on the bedrock range front are consistent with slip on a low-angle detachment system beneath the valley.  Finally, paleoseismic results from a trench at the southern end of the fault system suggest 3-4 surface ruptures during past ~4-5 ka, the most recent of which (MRE) occurred ~330-485 cal yr BP.  Scarps related to the MRE can be traced for at least ~50 km northward along the range front and imply surface displacements of 2-4 meters during this event.  Thus, we conclude that ongoing dextral shear along the margin of the Basin and Range is, in part, accommodated by co-seismic slip along low-angle detachment faults in Panamint Valley.  Our results have important implications for the interaction of fault networks and seismic hazard in the region.</p>

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