The lithostratigraphy of Cenozoic deposits along the south-east Cape coast as related to sea-level changes
Date
1989-08
Authors
Le Roux, F. G.
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
AFRIKAANSE OPSOMMING: Senosoiese sedimente langs die suidooskus van die
Kaapprovinsie is periodiek deur verskeie outeurs vir meer as
'n eeu bestudeer. In hierdie aanbieding word die
Iiteratuur saamgevat en vele dubbelsinnige stratigrafiese
onderverdelings en definisies opgeklaar.
Die Senosoiese afsettings kan volgens oorsprong
geklassifiseer word as marien, eolies en fluviaal. Die
mariene afsettings, synde strand-, nabystrand-, estuarien of
lagunale afsettings geassosieerd met transgressiewe/
regressiewe kusIyne, word nou op grond van kenmerkende
litologiese, paleontologiese sowel as ouderdomsverskille
onderverdeel in die Paleogeen Bathurst, Neogeen Alexandria
en Kwaternere Salnova Foraasies. Die Laat-Plioseen tot
Vroeg-Pleistoseen Nanaga Formasie, Middel- tot Laat-
Pleistoseen Nahoon Formasie en die Holoseen Schel• Hoek
Formasie vorm die kus-eoliese afsettings. AI die mariene
en marienverwante (eoliese} formasies, gekenmerk deur
kalkige klastiese afsettings, is saamgegroepeer in 'n
nuutgedefinieerde Algoa Groep. Fluviale afsettings word
onderverdeel in die Martindale, Kinkelbos, Bluewater Bay,
Kudus Kloof en Sunland Formasies.
Die onderskeie afsettings word gekorreleer met verskillende
seevlakstande deur geologiese tye.
Die vroegste Senosoiese
transgressiewe/regressiewe siklus het in die Vroeg-Paleoseen
begin en die hoogste aangetekende elevasie vir die era
bereik. Die Bathurst Formasie is waarskynlik gedurende
hierdie regressie afgeset. 'n Tweed~ kleiner transgressie/
regressiesiklus het plaasgevind gedurende die Laat-Eoseen
tot Vroeg-Oligoseen. Sover tans bekend, kan geen afsetting
in die dagsoomgebied van die Algoa Groep definitief met
hierdie siklus in verband gebring word nie. Die volgende
siklus, wat 'n transgressiewe maksimum van c. 250 m bereik
het, het begin in die Middel-Mioseen en verstryk in die
Vroee Plioseen. Mariene planasie van die kusplatform het
gedurende die transgressie plaasgevind terwyl die Alexandria
Formasie wat tans bo 120 m geleë is, gedurende die regressie
afgeset is. Die Vroeg-Plioseen transgressie het waarskynlik
'n maksimum huidige hoogte van c. 120 m bereik,
waartydens o.a. die 120 m branderstoep en "Humansdorpterras"
gekerf is. Die Alexandria Formasie tans geleë tussen 60 en
120 m, is afgeset gedurende die Laat-Plioseen regressie.
Hierdie regressie het verskeie relatief lang stilstande, wat
waarskynlik die 106-m, 90- tot 100-m en 84-m branderstoepe
verklaar, ondervind. Selfs die 60-m en 52-m kuslyne kon
tydens hierdie regressie gevorm het. Voorlopige
paleontologiese getuienis dui egter daarop dat die 60-m
kuslyn 'n transgressiewe maksimum van 'n daaropvolgende
siklus verteenwoordig, gevolg deur 'n regressie met minstens
een beduidende stilstand by 52 m. Die Alexandria Formasie
geleë tussen c. 60 en 30 m, is waarskynlik gedurende hierdie
regressie gedeponeer, waartydens ook die Bluewater Bay,
Kinkelbos en Kudus Kloof Formasies afgeset is.
Gedurende die Kwaternêre transgressie/regressiesiklusse,
waarvan minstens vier aangedui word, is die Salnova Formasie
(afwesig bo 30 m) afgeset. Die Nahoon Formasie, wat ook op
groot skaal op die kontinentale bank ontwikkel is, is
gedeponeer gedurende die laaste twee Pleistoseen glasiale
toe seevlakke tot benede -100 m gedaal het. Die Schelm
Hoek Formasie wat tans nog afgeset word, het ontstaan uit
die transgressiewe maksimum van die Flandriese transgressie
aan die begin van die Holoseen.
ENGLISH ABSTRACT: Cenozoic sediments along the south-east coast of the Cape Province have been studied intermittently for more than a century by various authors. In this presentation the literature is reviewed and many ambiguous stratigraphic subdivisions and definitions are clarified. The Cenozoic deposits can be classified, according to origin, as marine, aeolian and fluvial. The marine deposits, being lagoonal deposits either beach, nearshore, estuarine or associated with transgressive/regressive shorelines, are now subdivided on the grounds of distinct lithological, palaeontological as well as age differences into the Palaeogene Bathurst, Neogene Alexandria and Quaternary Salnova Formations. The Late Pliocene to Early Pleistocene Nanaga Formation, the Hiddle to Late Pleistocene Nahoon Formation and the Holocene Schelm Hoek Formation constitute the coastal and marine-related aeolian deposits. All the marine (aeolian) formations, which are characterised by calcareous clastics, have been grouped together in a newly defined Algoa Group. Fluvial deposits are subdivided into the Martindale, Kinkelbos, Bluewater Bay, Kudus Kloof and Sunland Formations. The various deposits are correlated with different stands of sea-level through geological time. The earliest Cenozoic transgression/regression cycle started in the Early Palaeocene and reached the highest recorded altitude for the era. The Bathurst Formation was probably deposited during this regression. A second lesser transgression/regression cycle occurred in the Late Eocene to Early Oligocene. As far as is presently known, no deposit in the outcrop area of the Algoa Group can be definitely related to this cycle. The next cycle, which reached a transgressive maximum of c. 250 m, started in the Middle Miocene and terminated in the Early Pliocene. Marine planation of the coastal platform took place during the transgression, whilst the Alexandria Formation presently situated above 120 m, was deposited during the regression. The Early Pliocene transgression is considered to have reached a maximum present-day elevation of c. 120 m, during which the 120 m marine bench and "Humansdorp Terrace", amongst others, were carved. The Alexandria Formation presently situated between 60 and 120 m, was deposited during the Late Pliocene regression, which experienced several relatively long stillstands which probably account for the 106 m, 90 t.o 100 m and 8.4 m benches. Even the 60 m- and 52 m-shorelines could have been formed during this regression. Preliminary palaeontological evidence, however, suggests that the 60 m shoreline represents a transgressive maximum of a subsequent cycle followed by a regression with at least one significant stillstand at 52 m. The Alexandria Formation situated between c. 60 and 30 m, was probably deposited during this regression, which also saw the deposition of the Bluewater Bay, Kinkelbos and Kudus Kloof Formations. During the Quaternary transgression/regression cycles, of which at least four are indicated, the Salnova Formation (absent above 30 m) was deposited. The Nahoon Formation, which is also extensively developed on the continental shelf, was deposited during the last two Pleistocene glacials, when sea-levels receded to less than -100 m. The Schelm Hoek Formation, which is still being deposited, originated from the transgressive maximum of the Flandrian transgression at the start of the Holocene.
ENGLISH ABSTRACT: Cenozoic sediments along the south-east coast of the Cape Province have been studied intermittently for more than a century by various authors. In this presentation the literature is reviewed and many ambiguous stratigraphic subdivisions and definitions are clarified. The Cenozoic deposits can be classified, according to origin, as marine, aeolian and fluvial. The marine deposits, being lagoonal deposits either beach, nearshore, estuarine or associated with transgressive/regressive shorelines, are now subdivided on the grounds of distinct lithological, palaeontological as well as age differences into the Palaeogene Bathurst, Neogene Alexandria and Quaternary Salnova Formations. The Late Pliocene to Early Pleistocene Nanaga Formation, the Hiddle to Late Pleistocene Nahoon Formation and the Holocene Schelm Hoek Formation constitute the coastal and marine-related aeolian deposits. All the marine (aeolian) formations, which are characterised by calcareous clastics, have been grouped together in a newly defined Algoa Group. Fluvial deposits are subdivided into the Martindale, Kinkelbos, Bluewater Bay, Kudus Kloof and Sunland Formations. The various deposits are correlated with different stands of sea-level through geological time. The earliest Cenozoic transgression/regression cycle started in the Early Palaeocene and reached the highest recorded altitude for the era. The Bathurst Formation was probably deposited during this regression. A second lesser transgression/regression cycle occurred in the Late Eocene to Early Oligocene. As far as is presently known, no deposit in the outcrop area of the Algoa Group can be definitely related to this cycle. The next cycle, which reached a transgressive maximum of c. 250 m, started in the Middle Miocene and terminated in the Early Pliocene. Marine planation of the coastal platform took place during the transgression, whilst the Alexandria Formation presently situated above 120 m, was deposited during the regression. The Early Pliocene transgression is considered to have reached a maximum present-day elevation of c. 120 m, during which the 120 m marine bench and "Humansdorp Terrace", amongst others, were carved. The Alexandria Formation presently situated between 60 and 120 m, was deposited during the Late Pliocene regression, which experienced several relatively long stillstands which probably account for the 106 m, 90 t.o 100 m and 8.4 m benches. Even the 60 m- and 52 m-shorelines could have been formed during this regression. Preliminary palaeontological evidence, however, suggests that the 60 m shoreline represents a transgressive maximum of a subsequent cycle followed by a regression with at least one significant stillstand at 52 m. The Alexandria Formation situated between c. 60 and 30 m, was probably deposited during this regression, which also saw the deposition of the Bluewater Bay, Kinkelbos and Kudus Kloof Formations. During the Quaternary transgression/regression cycles, of which at least four are indicated, the Salnova Formation (absent above 30 m) was deposited. The Nahoon Formation, which is also extensively developed on the continental shelf, was deposited during the last two Pleistocene glacials, when sea-levels receded to less than -100 m. The Schelm Hoek Formation, which is still being deposited, originated from the transgressive maximum of the Flandrian transgression at the start of the Holocene.
Description
Thesis (MSc)--University of Stellenbosch, 1989.
Keywords
Geology, Stratigraphic -- Cenozoic, Sedimentation and deposition, Marine sediments -- South Africa -- Cape of Good Hope, Southeastern, Formations (Geology) -- South Africa -- Cape of Good Hope, Southeastern, Dissertations -- Geology, Theses -- Geology