Revised definition/outline of the Kheis Terrane along the western margin of the Kaapvaal Craton and lithostratigraphy of the newly proposed Keis Supergroup

2019 ◽  
Vol 122 (2) ◽  
pp. 187-220 ◽  
Author(s):  
H.S. van Niekerk ◽  
N.J. Beukes
Keyword(s):  
South Africa ◽  
Satellite Imagery ◽  
Aerial Photography ◽  
Kaapvaal Craton ◽  
Thrust Belt ◽  
Western Margin ◽  
Fold And Thrust Belt ◽  
Stratigraphic Subdivision ◽  
Northern Cape ◽  
Transvaal Supergroup

Abstract The Kheis Province is situated between the Namaqua-Natal Province and the western margin of the Kaapvaal Craton in the Northern Cape Province of South Africa. It has been described as a thin-skinned fold and thrust belt formed between 1800 and 1700 Ma. The lithostratigraphic subdivision of the rock units comprising the Kheis Province has been a source of much controversy. From detailed study of aerial photography and satellite imagery, as well as field-based studies, the outcrop patterns in the Kheis Province and Kaaien Terrane were reinterpreted and a new stratigraphic subdivision is outlined here. It is proposed that the structural Kaaien Terrane and Kheis Province should be combined into the Kheis Terrane and that the rocks occurring in the Kheis Terrane should be grouped together to form the new Keis supergroup, with the basal metaconglomerate of the Mapedi/Gamagara Formation recognised as the regional unconformity between the Keis supergroup and the underlying rocks of the Transvaal Supergroup in the Griqualand West area. The Keis supergroup is subdivided from the base upwards into the Elim-, Olifantshoek-, Groblershoop- and Wilgenhoutsdrif groups. The basal Elim group is composed of the Mapedi/Gamagara- and Lucknow formations. It is overlain with a regional erosional unconformity by the Olifantshoek group, which is made up of the Neylan-, Hartley-, Volop- and Top Dog formations. The Olifantshoek group is conformably overlain by the Groblershoop group which is comprised of three upward coarsening successions:the Faanshoek- and Faansgeluk formations,the Maraisdraai- and Vuilnek formations andthe Opwag- and Skurweberg formations. The Groblershoop group is in turn erosively overlain by the rocks of the Wilgenhoutsdrif Group, which include the basal erosive Groot Drink formation which is overlain by the Zonderhuis- and Leerkrans formations. The lithologies of the Keis supergroup are in faulted contact with the rocks of the younger Areachap Group of the ~1200 Ma Namaqua-Natal Metamorphic Province.

Isotopic constraints on the Late Archean carbon cycle from the Transvaal Supergroup along the western margin of the Kaapvaal Craton, South Africa

2009 ◽  
Vol 169 (1-4) ◽  
pp. 15-27 ◽  
Author(s):  
W.W. Fischer ◽  
S. Schroeder ◽  
J.P. Lacassie ◽  
N.J. Beukes ◽  
T. Goldberg ◽  
...  
Keyword(s):  
South Africa ◽  
Carbon Cycle ◽  
Kaapvaal Craton ◽  
Western Margin ◽  
Transvaal Supergroup ◽  
Isotopic Constraints

Deformation of the western flank of the Andes at ~20–22°S: a contribution to the quantification of crustal shortening

2021 ◽  
Author(s):  
Tania Habel ◽  
Robin Lacassin ◽  
Martine Simoes ◽  
Daniel Carrizo ◽  
German Aguilar ◽  
...  
Keyword(s):  
Crustal Thickening ◽  
Thrust Belt ◽  
Mountain Building ◽  
Common View ◽  
Western Margin ◽  
The Andes ◽  
Kinematic Evolution ◽  
Western Flank ◽  
Fold And Thrust Belt ◽  
High Resolution Satellite Images

<p>The Andes are the case example of an active Cordilleran-type orogen. It is generally admitted that, in the Bolivian Orocline (Central Andes at ~20°S), mountain-building started ~50–60 Myr ago, close to the subduction margin, and then propagated eastward. Though suggested by some early geological cross-sections, the structures sustaining the uplift of the western flank of the Altiplano have often been dismissed, and the most common view theorizes that the Andes grow only by east-vergent deformation along its eastern margin. However, recent studies emphasize the significant contribution of the West Andean front to mountain-building and crustal thickening, in particular at the latitude of Santiago de Chile (~33.5°S), and question the contribution of similar structures elsewhere along the Andes.  Here, we focus on the western margin of the Altiplano at 20–22°S, in the Atacama desert of northern Chile. We present our results on the structure and kinematic evolution on two sites where the structures are well exposed. We combine mapping from high-resolution satellite images with field observations and numerical trishear forward modeling to provide quantitative constraints on the kinematic evolution of the western front of the Andes. Our results confirm two main structures: (1) a major west-vergent thrust placing Andean Paleozoic basement over Mesozoic strata, and (2) a west-vergent fold-and-thrust-belt deforming primarily Mesozoic units. Once restored, we estimate that both structures accommodate together at least ~6–9 km of shortening across the sole ~7–17 km-wide outcropping fold-and-thrust-belt. Further west, structures of this fold-and-thrust-belt are unconformably buried under much less deformed Cenozoic units, as revealed from seismic profiles. By comparing the scale of these buried structures to those investigated previously, we propose that the whole fold-and-thrust-belt has most probably absorbed at least ~15–20 km of shortening. The timing of the recorded main deformation can be bracketed sometime between ~68 and ~29 Ma – and possibly between ~68 and ~44 Ma – from dated deformed geological layers, with a subsequent significant slowing-down of shortening rates. This is in good agreement with preliminary modeling of apatite and zircon (U-Th)/He dates suggesting that basement exhumation by thrusting started by ~70–60 Ma, slowed down by ~50–40 Ma, and tended to cease by ~30–20 Ma. Minor shortening affecting the mid-late Cenozoic deposits indicates that deformation continued after ~29 Ma along the western Andean fold-and-thrust-belt, but remained limited compared to the more intense deformation that occured during the Paleogene. Altogether, the data presented here will provide a quantitative evaluation of the contribution of the western margin of the Altiplano plateau to mountain-building at this latitude, in particular at its earliest stages.</p>

scholarly journals Palaeomagnetism of the early Palaeoproterozoic, volcanic Hekpoort Formation (Transvaal Supergroup) of the Kaapvaal craton, South Africa

2017 ◽  
Vol 209 (2) ◽  
pp. 842-865 ◽  
Author(s):  
F. Humbert ◽  
L. Sonnette ◽  
M.O. de Kock ◽  
P. Robion ◽  
C.S. Horng ◽  
...  
Keyword(s):  
South Africa ◽  
Kaapvaal Craton ◽  
Transvaal Supergroup

Unraveling the contribution of the western margin of the Altiplano plateau in North Chile (20°S) to Andean mountain-building

2020 ◽  
Author(s):  
Tania Habel ◽  
Robin Lacassin ◽  
Martine Simoes ◽  
Daniel Carrizo
Keyword(s):  
Cross Sections ◽  
Crustal Thickening ◽  
Thrust Belt ◽  
Seismic Profiles ◽  
Mountain Building ◽  
Buried Structures ◽  
Common View ◽  
Western Margin ◽  
The Andes ◽  
Fold And Thrust Belt

<p><span>The Andes are the case example of an active Cordilleran-type orogen. It is generally admitted that, in the Central Andes (~20°S), mountain-building started ~50-60 Myr ago, close to the subduction margin, and then propagated eastward. Though suggested by some early geological cross-sections, the structures sustaining the uplift of the western flank of the Altiplano have been largely dismissed, and the most common view theorizes that the Andes grow only by east-vergent deformation along its eastern margin. However, recent studies emphasize the significant contribution of the West Andean front to mountain-building and crustal thickening, in particular at the latitude of Santiago de Chile (~33.5°S). The contribution of similar structures elsewhere along the Andes to the kinematics of the orogen is still poorly solved, because not yet well synthesized nor quantified. Here, we focus on the western margin of the Altiplano at 20°S, in the Atacama desert of northern Chile. We focus our work on two sites where structures are well exposed. <br>Our results confirm two main structures: (1) a major west-vergent thrust placing Andean Paleozoic basement over Mesozoic strata, and (2) a west-vergent fold-and-thrust-belt involving Mesozoic units. Once restored, we calculate a minimum of ~4 km of shortening across the sole ~10 km-wide outcropping fold-and-thrust-belt. Further west, structures of this fold-and-thrust-belt are unconformably buried under slightly deformed Cenozoic units, as revealed from seismic profiles. By comparing the scale of these buried structures to those investigated previously, we propose that the whole fold-and-thrust-belt has most probably absorbed ~15-20 km of shortening, sometime between ~68 Ma (youngest folded Mesozoic layers) and ~29 Ma (oldest unconformable Cenozoic layer). Preliminary (U-Th)/He thermochronological data suggest that basement exhumation by thrusting happened at the beginning of this ~40 Ma time span. Minor shortening affecting the mid-late Cenozoic deposits indicates that deformation continued after 29 Ma along the western Andean fold-and-thrust-belt, but remained limited compared to the more intense deformation during the Paleogene. Altogether, the data presented here will provide a quantitative evaluation of the contribution of the western margin of the Altiplano plateau to mountain-building at this latitude.</span></p>

scholarly journals PRELIMINARY GEOCHEMICAL AND SEDIMENTOLOGICAL ANALYSIS IN NW CORFU: THE MIOCENE SEDIMENTS IN AGIOS GEORGIOS PAGON

2017 ◽  
Vol 50 (1) ◽  
pp. 402 ◽  
Author(s):  
P. Tserolas ◽  
C. Mpotziolis ◽  
A. Maravelis ◽  
A. Zelilidis
Keyword(s):  
Calcium Carbonate ◽  
Organic Carbon ◽  
Source Rock ◽  
Organic Content ◽  
Sieve Analysis ◽  
Thrust Belt ◽  
Western Margin ◽  
Basin Development ◽  
Fold And Thrust Belt ◽  
Combined Use

A total of 80 samples of the Miocene deposits in Agios Georgios Pagon (NW Corfu) were selected and studied in regard of their geochemical and sedimentological characteristics. Organic content and calcium carbonate measurements were used and combined to investigate the depositional conditions and preliminary source rock potential. TOC analysis presented significant values ranging up to ~3% of organic carbon, with an average of 0,7%, and thus providing a promising basis for further assessment of their source rock potential. Calcium Carbonate measurements presented an average of ~27%. Fluctuations, correlative trends and the combined use of sieve analysis provide insights and alterations in the depositional conditions. The studied strata are part of an ongoing investigation throughout the Miocene to Pliocene sediment accumulations in Corfu, from Lefkimmi in the SW part to Agios Stefanos to the NW. The depositional conditions and source rock potential should provide new insights in understanding the geotectonic processes and basin development in the western margin of the Hellenic Fold and Thrust Belt.

scholarly journals Deepwater Fold-and-Thrust Belt Along New Caledonia's Western Margin: Relation to Post-obduction Vertical Motions

Tectonics ◽  
2017 ◽  
Vol 36 (10) ◽  
pp. 2108-2122 ◽  
Author(s):  
J. Collot ◽  
M. Patriat ◽  
S. Etienne ◽  
P. Rouillard ◽  
F. Soetaert ◽  
...  
Keyword(s):  
Thrust Belt ◽  
Western Margin ◽  
Fold And Thrust Belt
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