Abstract
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.