Plio‐Pleistocene Continental Hydroclimate and Indian Ocean Sea Surface Temperatures at the Southeast African Margin

Abstract

The Plio-Pleistocene encompasses large-scale changes in climate and may provide an analog for the function of Earth's ecosystems in a high carbon dioxide (CO 2) world. Pliocene climate was characterized by atmospheric CO 2 levels similar to today, reduced sea surface temperature (SST) gradients, and events such as the restriction of the Central American and Indonesian Seaways (Cane & Molnar, 2001; Fedorov et al., 2013). Despite its relative warmth and stability, the Pliocene is defined by long-term cooling that is potentially related to tectonic plate movement and consequent changes in ocean currents and pCO 2 drawdown, especially in the Indo-Pacific region (Cane & Molnar, 2001). The Plio-Pleistocene transition around 2.7 Ma is marked by the breakdown of Pliocene climate conditions, as strong SST gradients between the high-and low-latitudes and across the Pacific Ocean basin were established, and Northern Hemisphere glaciation intensified (Fedorov et al., 2013). The development of stronger zonal SST gradients in the Pacific Ocean was likely related to gradual thermocline shoaling in the Pliocene and an increase in tropical upwelling that led to strengthened Walker circulation (Ravelo et al., 2004). The interaction between these ocean-atmosphere feedbacks and changes in insolation potentially magnified the climate's sensitivity to obliquity, leading to the 41 kyr pacing of higher amplitude glacial cycles in the early Pleistocene (Ravelo et al., 2004).

Climatic Forcing of Plio‐Pleistocene Formation of the Modern Limpopo River, South Africa

“…3.3 Ma, the leaf wax carbon‐isotope record of ODP Site 1085 shows a 2‰ decrease, indicating C 3 plant expansion and increasing humidity across the southern African continent (Figure 2b; Maslin et al., 2012). The leaf wax hydrogen‐isotope record at IODP Site 1478 also shows progressively more negative δD wax values, consistent with the carbon‐isotope data from ODP Site 1085 (Figure 2c; Taylor et al., 2021). Together, this suggests that Late Pliocene climate change on the southern African continent may have promoted headwater erosion of the Limpopo River.…”

“…The formation of the modern Limpopo River during the Plio‐Pleistocene in an area lacking contemporaneous tectonic uplift suggests dominant climatic control on this recent evolution of the river. The first provenance shift documented in this study coincides in timing with climate wetting recorded by the leaf wax carbon‐isotope record of ODP Site 1085 and the leaf wax hydrogen‐isotope record of IODP Site 1478 (Figures 1a and 2; Maslin et al., 2012; Taylor et al., 2021). At ca.…”

“…(b) Southwest (SW) Africa ODP Site U1085 n‐alkane δ 13 C values (Maslin et al., 2012). (c) Southeast (SE) Africa IODP Site U1478 δD wax values (Taylor et al., 2021). (d) Whole‐round core magnetic susceptibility (MS) in Hole U1478A (Hall et al., 2017).…”

A Pliocene Precipitation Isotope Proxy‐Model Comparison Assessing the Hydrological Fingerprints of Sea Surface Temperature Gradients

“…( 2016 ) and Taylor et al. ( 2021 ) have timeseries that approximately resolve precessional pacing, showing that the “likely precessional” variability is around 10–20 per mil.…”

Sr‐Nd‐Hf isotopic constraints on the provenance of the modern Zambezi River sand sediments, southern Africa

“…The Zambezi River is the largest river in the southern African region (Figure 1), which has been transporting large amounts of sediments to the southwestern Indian Ocean likely since the Cretaceous (Moore, 1999; Spaliviero et al, 2014; Walford et al, 2005). Understanding the sediment source‐sink relationship from the upper to the lower reaches of the Zambezi River is not only a key to understanding sediment buffering/transportation processes but also essential to correctly interpreting erosion history and climate change of the southern African region (Baby et al, 2020; Just et al, 2014; Taylor et al, 2021), and formation of the Agulhas Current (Simon et al, 2020), as are recorded by borehole sediments from the International Ocean Discovery Program (IODP) 361 cruise (southeast African margin) (Figure 1a) (Hall et al, 2017). Here we present Sr‐Nd‐Hf isotopic data from different reaches of the Zambezi River to assess whether the upper reaches sediments can be transported to the lower reaches.…”