Structural and geochronological constraints of early Ross orogenic deformation in the Pensacola Mountains, Antarctica
During end-Neoproterozoic to early Paleozoic time, the southern margin of Gondwana was affected by widespread subduction-related orogenesis. In East Antarctica this event is known as the Ross orogeny, whose manifestation is exposed along the 3500 km length of the Transant-arctic Mountains. In the Pe...
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ftanucanberra:oai:openresearch-repository.anu.edu.au:1885/80336 2024-01-14T10:00:25+01:00 Structural and geochronological constraints of early Ross orogenic deformation in the Pensacola Mountains, Antarctica Curtis, Michael L Millar, Ian L Storey, Bryan Fanning, Christopher http://hdl.handle.net/1885/80336 https://doi.org/10.1130/B25170.1 unknown Association of Engineering Geologists 0016-7606 http://hdl.handle.net/1885/80336 doi:10.1130/B25170.1 Geological Society of America Bulletin Keywords: East Antarctica Mountains Orogenic deformation Ross orogeny Deformation Geochronology Granite Landforms Limestone Microstructure Shrinkage Stratigraphy Tectonics Structural geology Gondwana orogeny Proterozoic Antarctica East Antarctica Polyphase deformation Transantarctic Mountains Transpression Journal article ftanucanberra https://doi.org/10.1130/B25170.1 2023-12-15T09:37:27Z During end-Neoproterozoic to early Paleozoic time, the southern margin of Gondwana was affected by widespread subduction-related orogenesis. In East Antarctica this event is known as the Ross orogeny, whose manifestation is exposed along the 3500 km length of the Transant-arctic Mountains. In the Pensacola Mountains, the Ross orogeny is characterized by two contractional deformation events, which bracket a brief period of latest Middle Cambrian to early Late Cambrian extension and sedimentation. The oldest and most intense of these deformation events effected a succession of latest Neoproterozoic metagraywackes (Hannah Ridge Formation), producing tight to isoclinal F1 folds that possess a slaty axial-planar cleavage. Steeply plunging asymmetric F2 folds and their associated cleavage are superimposed upon the NNE-SSW D1 structural grain, forming a consistent clockwise oblique angle. Together with several shear-sense indicators, the angular relationship of D2 and D1 suggests that the F2 folds formed as a result of sinistral reactivation of D1 structures. At Serpan Peak, new meso- and microstructural observations of the Serpan Peak granite suite reveal two phases of emplacement: an early granodioritic phase emplaced prior to the regional D1 deformation event, and a later phase of syntectonic biotite granites emplaced during D2. New U-Pb SHRIMP ages for three phases of the Serpan Peak granite suite constrain their emplacement-and, by structural relationship, the early Ross D1 and D2 deformation events-as having occurred at 505 ± 5 Ma. The ages of D1 and D2 are identical within error, and we interpret them as being the product of a single progressive sinistral transpressional deformation event. Our new structural and geochronological constraints necessitate that deformation of the Hannah Ridge Formation occurred in conjunction with exhumation from lower greenschist conditions prior to deposition of the upper Middle Cambrian Nelson Limestone (< 10 m.y.). Exhumation was closely followed by ca. 500 Ma bimodal ... Article in Journal/Newspaper Antarc* Antarctica Arctic East Antarctica Australian National University: ANU Digital Collections Arctic East Antarctica Transantarctic Mountains Hannah ENVELOPE(-60.613,-60.613,-62.654,-62.654) Pensacola Mountains ENVELOPE(-58.000,-58.000,-83.500,-83.500) Hannah Ridge ENVELOPE(-54.992,-54.992,-83.605,-83.605) Serpan Peak ENVELOPE(-54.833,-54.833,-83.566,-83.566) Geological Society of America Bulletin 116 5 619 |
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Australian National University: ANU Digital Collections |
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Keywords: East Antarctica Mountains Orogenic deformation Ross orogeny Deformation Geochronology Granite Landforms Limestone Microstructure Shrinkage Stratigraphy Tectonics Structural geology Gondwana orogeny Proterozoic Antarctica East Antarctica Polyphase deformation Transantarctic Mountains Transpression |
spellingShingle |
Keywords: East Antarctica Mountains Orogenic deformation Ross orogeny Deformation Geochronology Granite Landforms Limestone Microstructure Shrinkage Stratigraphy Tectonics Structural geology Gondwana orogeny Proterozoic Antarctica East Antarctica Polyphase deformation Transantarctic Mountains Transpression Curtis, Michael L Millar, Ian L Storey, Bryan Fanning, Christopher Structural and geochronological constraints of early Ross orogenic deformation in the Pensacola Mountains, Antarctica |
topic_facet |
Keywords: East Antarctica Mountains Orogenic deformation Ross orogeny Deformation Geochronology Granite Landforms Limestone Microstructure Shrinkage Stratigraphy Tectonics Structural geology Gondwana orogeny Proterozoic Antarctica East Antarctica Polyphase deformation Transantarctic Mountains Transpression |
description |
During end-Neoproterozoic to early Paleozoic time, the southern margin of Gondwana was affected by widespread subduction-related orogenesis. In East Antarctica this event is known as the Ross orogeny, whose manifestation is exposed along the 3500 km length of the Transant-arctic Mountains. In the Pensacola Mountains, the Ross orogeny is characterized by two contractional deformation events, which bracket a brief period of latest Middle Cambrian to early Late Cambrian extension and sedimentation. The oldest and most intense of these deformation events effected a succession of latest Neoproterozoic metagraywackes (Hannah Ridge Formation), producing tight to isoclinal F1 folds that possess a slaty axial-planar cleavage. Steeply plunging asymmetric F2 folds and their associated cleavage are superimposed upon the NNE-SSW D1 structural grain, forming a consistent clockwise oblique angle. Together with several shear-sense indicators, the angular relationship of D2 and D1 suggests that the F2 folds formed as a result of sinistral reactivation of D1 structures. At Serpan Peak, new meso- and microstructural observations of the Serpan Peak granite suite reveal two phases of emplacement: an early granodioritic phase emplaced prior to the regional D1 deformation event, and a later phase of syntectonic biotite granites emplaced during D2. New U-Pb SHRIMP ages for three phases of the Serpan Peak granite suite constrain their emplacement-and, by structural relationship, the early Ross D1 and D2 deformation events-as having occurred at 505 ± 5 Ma. The ages of D1 and D2 are identical within error, and we interpret them as being the product of a single progressive sinistral transpressional deformation event. Our new structural and geochronological constraints necessitate that deformation of the Hannah Ridge Formation occurred in conjunction with exhumation from lower greenschist conditions prior to deposition of the upper Middle Cambrian Nelson Limestone (< 10 m.y.). Exhumation was closely followed by ca. 500 Ma bimodal ... |
format |
Article in Journal/Newspaper |
author |
Curtis, Michael L Millar, Ian L Storey, Bryan Fanning, Christopher |
author_facet |
Curtis, Michael L Millar, Ian L Storey, Bryan Fanning, Christopher |
author_sort |
Curtis, Michael L |
title |
Structural and geochronological constraints of early Ross orogenic deformation in the Pensacola Mountains, Antarctica |
title_short |
Structural and geochronological constraints of early Ross orogenic deformation in the Pensacola Mountains, Antarctica |
title_full |
Structural and geochronological constraints of early Ross orogenic deformation in the Pensacola Mountains, Antarctica |
title_fullStr |
Structural and geochronological constraints of early Ross orogenic deformation in the Pensacola Mountains, Antarctica |
title_full_unstemmed |
Structural and geochronological constraints of early Ross orogenic deformation in the Pensacola Mountains, Antarctica |
title_sort |
structural and geochronological constraints of early ross orogenic deformation in the pensacola mountains, antarctica |
publisher |
Association of Engineering Geologists |
url |
http://hdl.handle.net/1885/80336 https://doi.org/10.1130/B25170.1 |
long_lat |
ENVELOPE(-60.613,-60.613,-62.654,-62.654) ENVELOPE(-58.000,-58.000,-83.500,-83.500) ENVELOPE(-54.992,-54.992,-83.605,-83.605) ENVELOPE(-54.833,-54.833,-83.566,-83.566) |
geographic |
Arctic East Antarctica Transantarctic Mountains Hannah Pensacola Mountains Hannah Ridge Serpan Peak |
geographic_facet |
Arctic East Antarctica Transantarctic Mountains Hannah Pensacola Mountains Hannah Ridge Serpan Peak |
genre |
Antarc* Antarctica Arctic East Antarctica |
genre_facet |
Antarc* Antarctica Arctic East Antarctica |
op_source |
Geological Society of America Bulletin |
op_relation |
0016-7606 http://hdl.handle.net/1885/80336 doi:10.1130/B25170.1 |
op_doi |
https://doi.org/10.1130/B25170.1 |
container_title |
Geological Society of America Bulletin |
container_volume |
116 |
container_issue |
5 |
container_start_page |
619 |
_version_ |
1788065805434355712 |