Crustal architecture of the largest pull-apart basin in East Antarctica unveiled

2020 ◽  
Author(s):  
Laura Crispini ◽  
Fausto Ferraccioli ◽  
Egidio Armadillo ◽  
Andreas Läufer ◽  
Antonia Ruppel
Keyword(s):  
Tectonic Setting ◽  
Field Work ◽  
Strike Slip ◽  
East Antarctica ◽  
Large Igneous Province ◽  
Rift System ◽  
Study Region ◽  
Eastern Margin ◽  
Pull Apart Basin ◽  
Slip Deformation

<p>The West Antarctic Rift System (WARS) is known to have experienced distributed/wide mode extension in the Cretaceous, followed by narrow mode and variably oblique extension/transtension in the Cenozoic, the latter potentially linked to the onset of oceanic seafloor spreading within the Adare Basin (Davey et al., 2016, GRL). However, onshore the extent and impact of Cenozoic extension and transtension within the Transantarctic Mountains sector of East Antarctica is currently much less well-constrained from a geophysical perspective.</p><p>Here we combine aeromagnetic, aerogravity, land-gravity and bedrock topography imaging to help constrain the extent, architecture and kinematics of the largest Cenozoic pull-apart basin recognised so far in East Antarctica, the Rennick Graben (RG).</p><p>Enhanced potential field imaging reveals the extent of a Jurassic tholeiitic Large Igneous Province preserved within the RG and the inherited structural architecture of its basement, including remnants of uplifted ca 530-500 Ma arc basement in the northern Wilson Terrane and a ca 490-460 Ma subglacial thrust fault belt separating the Cenozoic western flank of the RG from the eastern margin of Wilkes Subglacial Basin (WSB).</p><p>The architecture of the RG is best explained in terms of a major composite right-lateral pull-part basin that extends from the Oates Coast to the Southern Cross Mountains block. We propose that Cenozoic strike-slip deformation kinematically connected the RG with both the western edge of the WARS and the eastern margin of the WSB. An earlier phase of left-lateral strike slip deformation is also emerging from recent geological field work in the study region but only relatively subtle offsets in aeromagnetic anomaly patterns are visible in currently available regional datasets.</p><p>We conclude that the RG is part of a wider distributed region of the continental lithosphere in East Antarctica that was deformed in response to an evolving Cenozoic transtensional tectonic setting that may have also affected enigmatic sub-basins such as the Cook Basins in the adjacent WSB region.</p>

scholarly journals Is pull-apart basin tectonic model feasible for the formation of Kashmir basin, NW Himalaya

2017 ◽  
Vol 16 (1) ◽  
Author(s):  
Afroz Ahmad Shah ◽  
Mohammad Noor Firdhaus bin Yassin ◽  
Muhammad Izzat Izzuddin bin Haji Irwan
Keyword(s):  
Tectonic Setting ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Nw Himalaya ◽  
Tectonic Model ◽  
Pull Apart Basin ◽  
Piggyback Basin ◽  
Kashmir Basin ◽  
Dextral Strike Slip Fault ◽  
Dextral Strike Slip

Kashmir Basin in NW Himalaya is considered a Neogene-Quatermary piggyback basin that was formed as result of the continent-continent collision of Indian and Eurasian plates. This model however is recently challenged by a pull-apart basin model, which argues that a major dextral strike-slip fault that runs through the Kashmir basin is responsible for its formation. And here it is demonstrated that this tectonic model is structurally unrealistic, and poses problems with geomorphology, geology, and tectonic setting of Kashmir basin. The major flaw of the model remains its orientation, and geometry, because a major dextral fault, which form a pull-apart basin, cannot cut through the center of a basin. It is therefore shown that the recently suggested pull-apart model is structurally impossible, and thus the Central Kashmir Fault (CKF), a proposed major dextral fault of Alam et al. (2015), could not exist.

Seismic doublets and a complex seismic sequence controlled by the rotation of the Juan Fernández microplate

2021 ◽  
Author(s):  
Simone Cesca ◽  
Carla Valenzuela Malebrán ◽  
José Ángel López-Comino ◽  
Timothy Davis ◽  
Carlos Tassara ◽  
...  
Keyword(s):  
Source Parameters ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Joint Analysis ◽  
Seismic Sequence ◽  
Local Data ◽  
Study Region ◽  
Coulomb Stress Changes ◽  
Earthquake Source Parameters ◽  
Stress Changes

<p> A complex seismic sequence took place in 2014 at the Juan Fernández microplate, a small microplate located between Pacific, Nazca and Antarctica plates. Despite the remoteness of the study region and the lack of local data, we were able to resolve earthquake source parameters and to reconstruct the complex seismic sequence, by using modern waveform-based seismological techniques. The sequence started with an exceptional Mw 7.1-6.7 thrust – strike slip earthquake doublet, the first subevent being the largest earthquake ever recorded in the region and one of the few rare thrust earthquakes in a region otherwise characterized by normal faulting and strike slip earthquakes. The joint analysis of seismicity and focal mechanisms suggest the activation of E-W and NE-SW faults or of an internal curved pseudofault, which is formed in response to the microplate rotation, with alternation of thrust and strike-slip earthquakes. Seismicity migrated Northward in its final phase, towards the microplate edge, where a second doublet with uneven focal mechanisms occurred. The sequence rupture kinematics is well explained by Coulomb stress changes imparted by the first subevent. Our analysis show that compressional stresses, which have been mapped at the northern boundary of the microplate, but never accompanied by large thrust earthquakes, can be accommodated by the rare occurrence of large, impulsive, shallow thrust earthquakes, with a considerable tsunamigenic potential.</p>

Late Pleistocene extension and strike-slip in the Dead Sea Basin

2004 ◽  
Vol 141 (5) ◽  
pp. 565-572 ◽  
Author(s):  
YUVAL BARTOV ◽  
AMIR SAGY
Keyword(s):  
Internal Structure ◽  
Slip Rate ◽  
Dead Sea ◽  
Strike Slip ◽  
Normal Faults ◽  
Small Scale ◽  
Dead Sea Basin ◽  
Pull Apart Basin ◽  
Western Border ◽  
The Dead

A newly discovered active small-scale pull-apart (Mor structure), located in the western part of the Dead Sea Basin, shows recent basin-parallel extension and strike-slip faulting, and offers a rare view of pull-apart internal structure. The Mor structure is bounded by N–S-trending strike-slip faults, and cross-cut by low-angle, E–W-trending normal faults. The geometry of this pull-apart suggests that displacement between the two stepped N–S strike-slip faults of the Mor structure is transferred by the extension associated with the normal faults. The continuing deformation in this structure is evident by the observation of at least three deformation episodes between 50 ka and present. The calculated sinistral slip-rate is 3.5 mm/yr over the last 30 000 years. This slip rate indicates that the Mor structure overlies the currently most active strike-slip fault within the western border of the Dead Sea pull-apart. The Mor structure is an example of a small pull-apart basin developed within a larger pull-apart. This type of hierarchy in pull-apart structures is an indication for their ongoing evolution.

scholarly journals Geology of the Mesoproterozoic Pillar Lake Volcanics and Inspiration Sill, Armstrong, Ontario: Evidence of Early Midcontinent Rift Magmatism in the Northwestern Nipigon Embayment

2021 ◽  
Author(s):  
Pete Hollings ◽  
Mark Smyk ◽  
Wouter Bleeker ◽  
Michael A. Hamilton ◽  
Robert Cundari ◽  
...  
Keyword(s):  
North America ◽  
Direct Contact ◽  
Large Igneous Province ◽  
Rift System ◽  
Flood Basalts ◽  
Midcontinent Rift ◽  
Igneous Province ◽  
Intrusive Rocks ◽  
Midcontinent Rift System ◽  
Northern Edge

The Midcontinent Rift System of North America is a ~1.1 Ga large igneous province comprising mainly flood basalts and intrusive rocks. We present new data for the Pillar Lake Volcanics and Inspiration Sill from the northern edge of the Midcontinent Rift in the northwestern Nipigon Embayment. The Pillar Lake Volcanics comprise a ~20-40 m-thick, flat-lying sequence of mafic pillowed and massive flows, pillowed flow breccia, and hyaloclastite breccia. They are characterized by SiO2 of 52-54 wt%, TiO2 of 1.2 to 1.3 wt% and K2O of 0.9 to 1.1 wt%. They are LREE-enriched, with La/Smn of 3.0 to 4.4 with fractionated HREE (Gd/Ybn = 1.4 to 1.7). The Inspiration diabase sill is < 50 m thick and is in direct contact with the underlying Pillar Lake Volcanics. Baddeleyite and zircon data from the Inspiration Sill yield a combined U-Pb upper intercept age of 1105.6 ± 1.6 Ma. The Inspiration Sill is characterized by uniform SiO2 of 52 to 53 wt%, TiO2 of 1.1 to 1.2 and K2O of 0.9 to 1.2 wt%. Inspiration Sill samples are LREE enriched with La/Smn of 3.2 to 3.3 and fractionated HREE of (Gd/Ybn = 1.6). The Pillar Lake Volcanics are at least 1120 Ma, and perhaps as old as 1130 Ma and represent an early, thin, and restricted mafic volcanic sequence, largely preserved below the younger Inspiration Sill. The Pillar Lake Volcanics and Inspiration Sill display a marked geochemical similarity, suggesting that they may represent magmatism associated with the earliest stages of Midcontinent rifting.

Evidence of extensional and strike-slip deformation in the offshore Gökova-Kos area affected by the July 2017 Mw6.6 Bodrum-Kos earthquake, eastern Aegean Sea

2018 ◽  
Vol 38 (3) ◽  
pp. 211-225 ◽  
Author(s):  
Neslihan Ocakoğlu ◽  
Paraskevi Nomikou ◽  
Yeliz İşcan ◽  
Maria Filomena Loreto ◽  
Danai Lampridou
Keyword(s):  
Aegean Sea ◽  
Strike Slip ◽  
Eastern Aegean ◽  
Slip Deformation ◽  
Eastern Aegean Sea

The Geometry and Symbolic Architecture of Basque Stone Octagons: The Pastoral Sarobe

2021 ◽  
Author(s):  
Roslyn M Frank
Keyword(s):  
Bronze Age ◽  
Architectural Design ◽  
Cultural Practices ◽  
Basque Country ◽  
Field Work ◽  
Study Region ◽  
Carbon 14 ◽  
The Past ◽  
Local Tradition ◽  
Cardinal Directions

<p>In the Basque Country (Euskal Herria) stone octagons, known as <em>sarobe</em> in Basque (Euskara), were built using specified dimensions, based on a “geometric foot” standard (0.278m). This standard was incorporated into a septarian system of measurements, e.g., rods of 7 g.ft. in length, called <em>gizabete</em>, poles of 21 g.ft. and a unit called <em>gorapila</em> of 49 g.ft. The dimensions of the stone octagons suggest that ritual importance was attributed to their geometric design, to the size of their perimeter and their orientation. According to local tradition and Basque legal codes, the eight stones on the perimeter had to be oriented to the cardinal and inter-cardinal directions. Field work indicates that over 500 octagons may have existed inside Euskal Herria at some point in the past. In the study region the stone octagons are linked specifically to localized transhumant practices of Basque-speaking shepherds, well documented socio-cultural practices that appear to date back to the Late Bronze Age if not earlier. Inferential evidence suggests that the cognitive origins of their architectural design might reach back to the Neolithic and be related to similar pastoral traditions as well as septarian units of measure encountered along the Atlantic façade. Thus far, even though several of the sites have been Carbon-14 dated, the absolute <em>terminus ante quem non</em> of the design of the octagons is still uncertain.</p>

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