Cape cliffs once teemed with mammals now lost forever

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Cape cliffs once teemed with mammals now lost forever

Scientists have found tracks of long-extinct beasts in rocky cliffs near Still Bay that were once dunes

Journalist


If you try to imagine the rugged coastline made of cliffs in the southern Cape around 220,000 years ago, you would have to imagine something completely different: a series of dunes teeming with life including some large and magnificent mammals that have since died out.
The remote coastline just east of Still Bay is home to cliffs which have in recent years become a treasure trove to ichnologists (scientists studying trace fossils) who pieced together which animals might have roamed there before the dunes turned to rock.
Two large rocks, some 400m apart, were found in the region, but not in the positions they were in when the animals pressed their feet into the matter as they made their way across the landscape.
The one rock, named Roberts Rock by the scientists, has since slid into the ocean, while the other, Megafauna Rock, now lies at the base of a coastal cliff.
The rocks, according to lead author Charles Helm, “provide windows into Late Pleistocene dune life in the southern Cape, and suggest an area teeming with life”.
Helm is a Canadian researcher who led a team of SA scientists, and their work was published in the latest edition of the SA Journal of Science.
The scientists have found “the first documentation of elephant tracks, probably the first rhinoceros and giant Cape horse tracks, and ichnological evidence of the long-horned buffalo”.
The giant Cape horse and long-horned buffalo are now extinct.
There are also traces of “medium and small artiodactyls, golden mole, birds and invertebrates”.
The rocks contained a variety of individual tracks, burrow traces and invertebrate trace fossils on multiple bedding planes, according to the scientists.
But, like most such studies, it is the work of scientists in other disciplines that either corroborates or disrupts the theories. In this case, the trace fossils fitted in with the skeletal fossil record from the area.
“Analysis and description of these track sites confirms the potential of ichnology to complement the skeletal fossil record and to enhance the understanding of Pleistocene life in southern Africa,” say the scientists, who described the two rocks as “remarkable fossil track sites”.
What’s also important is that these environments are unstable which means that the scientists have to make as many trips as possible to the sites before they disappear into the mists of the past.
Roberts Rock actually slumped into the ocean in 2016, making the research already done even more precious for the records.
On the flipside, changes in the environment also turn up new clues. “New sites frequently become exposed. This scenario stresses the need for regular ichnological surveys along this track-rich coastline to monitor existing sites and to search for new sites,” say the scientists.
The “instability of the slope and proximity to the ocean” had made Roberts Rock vulnerable to slumping and to wave action.
Multiple visits to the site demonstrated bedding-plane splitting of the block into two halves, with the appearance of further tracks on the newly exposed surfaces.
By 2016, Roberts Rock was no longer present, but that was when the more recently fallen Megafauna Rock became apparent to the researchers.
They say that repeated visits to this coastline are important “both to monitor the fate of known sites and to search for newly exposed trace fossil surfaces”.
“The slumping of Roberts Rock into the ocean is a loss to ichnology, mitigated by its replacement by an even larger track-bearing rock [Megafauna Rock],” they said.

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