<abstract xmlns="http://www.w3.org/1999/xhtml">

<p>The Gondwana Late Palaeozoic Ice Age is probably best represented by the Dwyka Group in South Africa. Striated and grooved surfaces or pavements are commonly considered to have formed subglacially, as are diamictites which have been interpreted as <italic>in-situ</italic> or reworked tillites. These interpretations were tested by investigation of outcrops in formerly well-studied areas, throughout South Africa. Detailed analyses have focused on striated surfaces/pavements and surface microtextures on quartz sand grains in diamictites. The sedimentological context of four pavements, interpreted to be glaciogenic, display features commonly associated with sediment gravity flows, rather than glaciation. A total of 4,271 quartz sand grains were subsampled from outcrops that are considered mainly to be tillites formed by continental glaciation. These grains, analysed by SEM, do not demonstrate the characteristic surface microtexture combinations of fracturing and irregular abrasion associated with Quaternary glacial deposits, but mainly a mix of surface microtextures associated with multicyclical grains. The Dwyka Group diamictites warrant reinterpretation as non-glacial sediment gravity flow deposits.</p>
</abstract>

The Gondwana Late Palaeozoic Ice Age is probably best represented by the Dwyka Group in South Africa. Striated and grooved surfaces or pavements are commonly considered to have formed subglacially, as are diamictites which have been interpreted as in-situ or reworked tillites. These interpretations were tested by investigation of outcrops in formerly well-studied areas, throughout South Africa. Detailed analyses have focused on striated surfaces/pavements and surface microtextures on quartz sand grains in diamictites. The sedimentological context of four pavements, interpreted to be glaciogenic, display features commonly associated with sediment gravity flows, rather than glaciation. A total of 4,271 quartz sand grains were subsampled from outcrops that are considered mainly to be tillites formed by continental glaciation. These grains, analysed by SEM, do not demonstrate the characteristic surface microtexture combinations of fracturing and irregular abrasion associated with Quaternary glacial deposits, but mainly a mix of surface microtextures associated with multicyclical grains. The Dwyka Group diamictites warrant reinterpretation as non-glacial sediment gravity flow deposits.

Reconsidering the glaciogenic origin of Gondwana diamictites of the Dwyka Group, South Africa

Geologos

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

The Gondwana Late Palaeozoic Ice Age is probably best represented by the Dwyka Group in South Africa. Striated and grooved surfaces or pavements are commonly...

Reconsidering the glaciogenic origin of Gondwana diamictites of the Dwyka Group, South Africa

Publié en ligne: 13 oct. 2022

Pages: 83 - 113

Reçu: 20 févr. 2022

Accepté: 15 juil. 2022

DOI: https://doi.org/10.2478/logos-2022-0008

Mots clés
Surface microtexture, sediment gravity flow, Late Palaeozoic Ice Age, pavement, Nooitgedacht

© 2022 Mats O. Molén et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Reconsidering the glaciogenic origin of Gondwana diamictites of the Dwyka Group, South Africa

Publié en ligne: 13 oct. 2022

Pages: 83 - 113

Reçu: 20 févr. 2022

Accepté: 15 juil. 2022

DOI: https://doi.org/10.2478/logos-2022-0008

Mots clésSurface microtexture, sediment gravity flow, Late Palaeozoic Ice Age, pavement, Nooitgedacht

© 2022 Mats O. Molén et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Mots clés
Surface microtexture, sediment gravity flow, Late Palaeozoic Ice Age, pavement, Nooitgedacht