{"title":"Mapping a 300-million-year old glacier bed: The Noordoewer section, Orange River, Namibia","authors":"D.P. Le Heron, P. Mejías Osorio, R. Wohlschlägl","doi":"10.1016/j.gr.2025.05.024","DOIUrl":null,"url":null,"abstract":"<div><div>Glacial geomorphological structures produced during the Late Palaeozoic Ice Age (LPIA) of Namibia provide exceptional insight into the flow direction, flow behaviour, and plumbing of subglacial drainage systems in deep time. At Noordoewer (southern Namibia), along the Orange River, a unique and largely undocumented ∼300 Ma assemblage of subglacial structures within the Dwyka Group is investigated. A detailed geological map documents a complex array of both hard- and soft-bed features shaped by the combined action of subglacial abrasion and meltwater. Structures trend parallel to the Orange River, supporting the view that part of its course originated as a Late Carboniferous valley. Key glacial indicators in a hard bedrock area developed on the Nama Group (Ediacaran metasediments) include (i) striated pavements, (ii) multiple roches moutonnées, and (iii) meltwater channels / p-forms. In areas comprising either a veneer or sheet of sandy diamictite, additional soft subglacial bed features are recognised, including (iv) a flute field, (v) soft-sediment striated surfaces (SSSS) and (vi) glaciotectonic structures including deformation bands. Collectively, these six sets of features support a NNW-directed palaeoflow, in direct contrast to previous interpretations of a southward or westward glacial flow down the axis of the Karasburg Basin. Thus, the new findings have broad implications for reconstructing past ice sheet dynamics and interpreting the geological record of glacial landscapes in the Late Palaeozoic record.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"146 ","pages":"Pages 163-172"},"PeriodicalIF":7.2000,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Gondwana Research","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1342937X25001868","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Glacial geomorphological structures produced during the Late Palaeozoic Ice Age (LPIA) of Namibia provide exceptional insight into the flow direction, flow behaviour, and plumbing of subglacial drainage systems in deep time. At Noordoewer (southern Namibia), along the Orange River, a unique and largely undocumented ∼300 Ma assemblage of subglacial structures within the Dwyka Group is investigated. A detailed geological map documents a complex array of both hard- and soft-bed features shaped by the combined action of subglacial abrasion and meltwater. Structures trend parallel to the Orange River, supporting the view that part of its course originated as a Late Carboniferous valley. Key glacial indicators in a hard bedrock area developed on the Nama Group (Ediacaran metasediments) include (i) striated pavements, (ii) multiple roches moutonnées, and (iii) meltwater channels / p-forms. In areas comprising either a veneer or sheet of sandy diamictite, additional soft subglacial bed features are recognised, including (iv) a flute field, (v) soft-sediment striated surfaces (SSSS) and (vi) glaciotectonic structures including deformation bands. Collectively, these six sets of features support a NNW-directed palaeoflow, in direct contrast to previous interpretations of a southward or westward glacial flow down the axis of the Karasburg Basin. Thus, the new findings have broad implications for reconstructing past ice sheet dynamics and interpreting the geological record of glacial landscapes in the Late Palaeozoic record.
期刊介绍:
Gondwana Research (GR) is an International Journal aimed to promote high quality research publications on all topics related to solid Earth, particularly with reference to the origin and evolution of continents, continental assemblies and their resources. GR is an "all earth science" journal with no restrictions on geological time, terrane or theme and covers a wide spectrum of topics in geosciences such as geology, geomorphology, palaeontology, structure, petrology, geochemistry, stable isotopes, geochronology, economic geology, exploration geology, engineering geology, geophysics, and environmental geology among other themes, and provides an appropriate forum to integrate studies from different disciplines and different terrains. In addition to regular articles and thematic issues, the journal invites high profile state-of-the-art reviews on thrust area topics for its column, ''GR FOCUS''. Focus articles include short biographies and photographs of the authors. Short articles (within ten printed pages) for rapid publication reporting important discoveries or innovative models of global interest will be considered under the category ''GR LETTERS''.