SEDIMENTOLOGY AND TAPHONOMY OF AN EARLY PLIOCENE SIVATHERE BONEBED AT THE WEST COAST FOSSIL PARK, SOUTH AFRICA.
Presenter: Roger Smith and Pippa Haarhoff; Evolutionary Studies Institute, University of the Witwatersrand , Johannesburg
Date: Thursday 28 July 2022
Time: 17:30
Venue: Auditorium Ministry of Mines
The West
Coast Fossil Park (WCFP) is a National Heritage Site and a public access
palaeo-tourism venture situated in a rehabilitated phosphate mining area
covering 716 ha. The site is located near Langebaan, about 120 km from Cape
Town. Scientifically, the WCFP represents possibly the greatest diversity of
fossils found anywhere in the world dated to the Miocene/Pliocene transition
(about 5.2 million years ago). It is also one of the very few sites in Africa
where actual fossil remains can be viewed in situ, and is
ranked amongst the best education and palaeo-tourism destinations in the
world.
In 1976
Brett Hendey excavated 4 trenches (1mx4m) into the 0.5 metre-thick bonebed in
the floor of the Langebaanweg phosphate mine and in doing so recovered at least
1 million specimens that form the bulk of the Cainozoic collections at Iziko
South African Museum. He interpreted the bonebed as having accumulated within a
flood channel along the northern bank of the former Berg River estuary. He
noted that the fossils were concentrated on the side and downstream of a
phosphate rock outcrop and proposed that this rock had obstructed the flow
causing the bones to accumulate (Hendey 1982). From 1998-2007 Roger Smith’s
research team tested this hypothesis with sedimentological and taphonomic
analyses of 75 m2 of carefully exhumed bonebed. Visiting the exposed bonebed
now forms the core experience at the West Coast Fossil Park.
Most of the
bones remaining in the dig site belong to sub adult sivatheres. There is
however a skewed distribution toward post-cranial elements, especially ribs and
vertebrae. Skull roofs (with horn cores) are under-represented in the sampled
portion of the bone bed. There is a strong indication from the spatial
distribution of the larger bones that the phosphate rock outcrop at the
southern end of the dig had an influence on the accumulation and the burial of
several sivathere skeletons. Bone "trains" that appear to originate
from individual skeletons indicate a style of disarticulation and dispersal
that is mainly governed by gravity rather than hydraulic sorting. Bone damage
patterns show numerous long bones with point compression fractures and arcuate "greenstick"
breaks interpreted as the result of trampling by hoofed animals during and
immediately after burial whilst the sediment was still unconsolidated. Scratch
marks on some of the bones are consistent with trampling rather than scavenging
although there are rare indications of paired puncture marks that are most
likely made by hyena-sized carnivores.
It is concluded that Hendey’s hypothesis for the bone bed environment of an intermittent fluvial channel in an estuarine setting is basically correct but it is evident that not all the animals arrived at the site during flood events. It is most likely that the scour pool provided a waterhole for herds of savanna animals and an aquatic microhabitat habitat for frogs and fishes. Other micro-vertebrate concentrations, in particular golden moles, were added directly to the scour pool probably from regurgitates of owls and other raptors that used the rock as a perch. The fact that sivatheres are over- represented possibly reflects they were gregarious and susceptible to mass drowning episodes similar to migrating Wildebees crossing the East African Mara river today.
For more information please contact the geological Society via geolsocnamibia@gmail.com

The late Paleozoic glaciation and its
paleofjords in northwestern Namibia
Presenter: Eduardo Rosa
Date: Thursday 28 July 2022
Time: 18:30
Venue: Auditorium Ministry of Mines
The late
Paleozoic glaciation and its paleofjords in northwestern Namibia
The Kunene
Region in northwestern Namibia hosts an outstanding and relatively untouched
deep-time glacial landscape. Major modern rivers flow through an exhumed
network of U-shaped glacial valleys carved on bedrock by Gondwanan glaciers and
filled with the glaciomarine Dwyka Group and post-glacial sediments during the
late Paleozoic Ice Age (362-256 Ma). This paleofjord network in Namibia has
provided evidence to support the hypothesis of an ice sheet placed in southern
Africa feeding outlet glaciers into the eastern margin of the Paraná Basin
seaway in South America. Despite these fjords being widely considered in
regional paleogeographic reconstructions, their sedimentary fill and glacial
dynamics are poorly known. Detailed field-based investigation linked with
satellite and drone imagery in the Namibian fjord network are allowing new
outcomes regarding this paleolandscape of glacial erosion, the nature of the
glacial and post-glacial stratigraphic record, and the significance of
gravitational resedimentation in fjord depositional systems.
For more information please contact the geological Society via geolsocnamibia@gmail.com
