Provenance analyses of neoproterozoic/early palaeozoic glacial (?) deposits from southwestern Gondwana

• Main Author: Van Staden, Anelda
• Format: Thesis
• Language: unknown
• Published: 2012
• Subjects: Provenance analyses; Glacial deposits; Gondwana (Continent); Argentina; Table Mountain; Ice Sheet
• Online Access: http://hdl.handle.net/10210/5012

Ph.D. Louis Agassiz first raised the concept of a global ice age followed by an intriguing history of both proponents and opponents of the idea simultaneously contributing towards the evolution of geological notions up to the present-day ‘Snowball Earth’ model. The causes of glaciation and the sedimentary, geochemical and stratigraphic feedbacks subsequently received renewed interest. Different deposits of possible Neoproterozoic glacial successions were thus selected for detailed provenance analyses in this study. The successions selected are the Puncoviscana Formation on the Pampia Terrane (Northwestern Argentina), the Sierra del Volcán diamictite of the Tandilia System on the Río de la Plata craton (Eastern Argentina), the Kaigas and Numees Formations of the Richtersveld and Gariep areas on the Kalahari craton (Northwest South Africa and Southern Namibia) and the Karoetjes Kop Formation and Swartleikrans Bed of the Bloupoort Formation of the Vanrhynsdorp region on the Kalahari craton (Western South Africa). Diagnostic physicochemical aspects are utilized to ascertain whether the deposits studied are firstly of glacial derivation and, secondly, to constrain the provenance of every deposit. The latter culminate with identification of a regionally or globally significant event. The Sierra del Volcán diamictite is a glacial diamictite with a depositional age younger than 485±2 Ma and is correlatable with the Upper Ordovician Pakhuis Formation (Table Mountain Group) in South Africa. The recognition of a glacial deposit of Upper Ordovician age in eastern Argentina suggests that the Hirnantian ice sheet cover extended from southwest South Africa to eastern Argentina, stretching from the central Paraná basin across into central and northwest Argentina and southern Bolivia. A proximal glacial marine depositional environment is inferred within a subaqueous outwash fan deposited by sediment gravity flow. Periglacial deposits occur in the Pakhuis Formation, suggesting that the ice sheet had retreated with deposition in glacial outwash plains by braided river systems and windblown loess.