GEOCHEMISTRY OF PALINGKLOOF SILTSTONES NEAR THE VERTEBRATE-DEFINED PTB AT TWEEFONTEIN, SOUTH AFRICA
Paleosol proxies provide a means to reconstruct paleoclimate, although their accuracy depends on whether siltstones actually represent paleosols. Our research goal is to test the hypothesis that interprets most siltstone deposits surrounding the PTB as paleosols rather than channel-fill deposits. At Tweefontein, a 15 m thick homogenous interval of green-gray to mottled reddish-gray siltstone was studied. Total Organic Carbon (TOC) analysis identified carbon-enriched intervals indicative of potential A horizons. Elemental analysis of these intervals using XRF allowed for the identification of geochemical trends.
Significant trends for several major elements exist in our Tweefontein section. TOC analysis reveals positive excursions at multiple intervals, which may be indicative of paleosol profiles. Parallel trends exist for Na, Mg, and Ti, with Na and Mg exhibiting synchronous positive excursions throughout the profile in concert with negative excursions of Ti. However, as other major elements appear to exhibit no significant geochemical trends and calculated weathering indices are ambiguous, these data are inconclusive for the presence of paleosols.