The geology of the northern Algoa basin, Port Elizabeth
Date
1972-04
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: The chief object of this study was to gain insight into the geological events which were connected with the earliest development of
the Northern Algoa Basin. Of particular interest was the nature,
origin, and stratigraphic significance of the Suurberg basalts and
tuffs which are exposed along the periphery of the basin.
The main conclusions of the study are the following:
i) A marked angular unconformity separates the Mesozoic rocks
(including the Suurberg volcanics) within the Algoa Basin
from the underlying Paleozoic "floor". No evidence was
found to support the existence of the post-Enon "Zuurberg
Fault" which had been postulated by earlier workers.
ii) The Suurberg volcanic rocks antedate the overlying Uitenhage beds, but the time interval between the two rock groups
is small.
iii) The Suurberg Group can be subdivided into three rock units.
The oldest, the Slagboom Formation, consists mainly of
quartzite breccia, which appears to represent the initial
vent-opening phase of the volcanism. This is followed by
the Coerney Formation which is composed of rhyolitic ash-fall
and ash-flow tuffs. The uppermost Mimosa Formation embraces
tholeiitic basalt, a few dolerite dykes, and thin interbedded
acidic tuffs.
iv) The volcanism was a local phenomenon within the Cape Folded
Belt and took place subaerially. Eruptions were of a linear
type, with the ascend of magmas probably related to pre-Uitenhage faulting. The distribution of volcanic materials was
largely controlled by the paleotopography.
v) The volcanic rocks originated from two unrelated (though
contemporaneously erupted) magmas. The basaltic magma was
probably generated in the upper mantle through partial melting and fractionation, while an anatectic origin is indicated
for the rhyolitic magma. No intermediate types occur.
vi) The Northern Algoa Basin was initiated by downwarping and
crustal subsidence, which only followed after the extrusion
of the Suurberg basalts.
Description
Maps scanned in multiple parts
Thesis (M. Sc.) -- University of Stellenbosch, 1972.
Thesis (M. Sc.) -- University of Stellenbosch, 1972.
Keywords
Geology -- South Africa -- Port Elizabeth -- Algoa Basin, Geology, Stratigraphic -- South Africa-- Port Elizabeth -- Algoa Basin, Volcanic ash, tuff, etc., Paleontology -- Mesozoic, UCTD