Terrigenous input and paleoproductivity in the Southern Ocean

Abstract

Abstract. The geochemistry of several sites along the Polar Front Zone of the Southern Ocean revealed significant changes in terrigenous input and productivity on glacial timescales. Our records indicate concentrations and fluxes of terrigenous elements (i.e., Fe, A1, and Ti) are low during interglacials and increase tenfold to twentyfold during glacials. Phosphorus accumulation, reactive P concentrations, and P/Ti ratios exhibit similar trends as the terrigenous components, suggesting increased export production during glacials. In all cores, elemental ratios remain relatively constant, indicating terrigenous sources at each site have not likely varied over the past •250 kyr. Iron accumulation rates for these sites are 10 times higher during glacials than interglacials and exceed the estimated regional eolian fluxes by •50 times. The source of this terrigenous material is thus likely to be hemipelagic rather than direct eolian input or ice rafting, and we speculate Fe upwelled from this source may have stimulated glacial productivity in the Southern Ocean.

Phylogenomics of the killer whale indicates ecotype divergence in sympatry

“…Both S-DIVA and BB suggested that killer whales expanded from the Southern Ocean into the North Pacific, with North Atlantic ecotypes diverging from North Pacific lineages, and the divergence between North Pacific ecotypes occurring locally in sympatry (Figure 2; Supplementary Figure 3). Ancestry in the Southern Oceans is consistent with the present day abundance of killer whales in the region, and the relative stability of that habitat over the course of the Quaternary (Francois et al, 1997;Latimer and Filippelli, 2001). Inference about dispersal and vicariance from the BB model is shown in Figure 2.…”

Environmental conditions during the Toarcian Oceanic Anoxic Event (T-OAE) in the westernmost Tethys: influence of the regional context on a global phenomenon

“…The P/Ti ratio reflects excessive phosphorous delivery to the sea-bottom not supported by terrigenous components. For this reason, an increase in the P/Ti ratio implies higher phosphorous sedimentation to the sea-bottom from biological processes (Latimer & Filippelli 2001, Flores et al 2005, Sen et al 2008. Of additional importance is the relationship of uranium with organic matter in the sediment; high values of U/Al ratio would be congruent with high values in other palaeoproductivity proxies (Nagao & Nakashima 1992, Baturin 2002.…”

“…The most extensively used geochemical proxy for palaeoproductivity reconstructions is Ba enrichment in marine sediments (e.g., Dehairs et al 1987, Bishop 1988, Dymond et al 1992, Van Os et al 1994, Francois et al 1995, Paytan et al 1996, Martínez-Ruiz et al 2000, Turgeon & Brumsack 2006, Gallego-Torres et al 2007, Reolid & Martínez-Ruiz 2012, but the Ba excess as a palaeoproductivity proxy must be applied with caution because the Ba concentrations can be significantly modified by secondary processes. Others geochemical proxies commonly used to interpret relative fluctuations in productivity are P/Ti ratio (Latimer & Filippelli 2001, Robertson & Filippelli 2008, Reolid & Martínez-Ruiz 2012, Reolid et al 2012a and Sr/Al ratio (Niebuhr 2005, Sun et al 2008, Reolid et al 2012a. The P/Ti ratio reflects excessive phosphorous delivery to the sea-bottom not supported by terrigenous components.…”

Comparison of benthic foraminifera and geochemical proxies in shelf deposits from the Upper Jurassic of the Prebetic (southern Spain)

“…The P/Ti ratio reflects excessive phosphorous delivery to the sea-bottom not supported by terrigenous components. For this reason, an increase in the P/Ti ratio implies higher phosphorous sedimentation to the sea-bottom from biological processes (Latimer and Filippelli, 2001;Flores et al, 2005;Sen et al, 2008;Reolid et al, 2012). Usually the P is released as PO [3][4] from decaying organic matter during bacterial degradation below the sediment water interface.…”

“…Thus, Latimer and Filippelli (2001) and Robertson and Filippelli (2008) use the P/Ti ratio, while Sun et al (2008) also study the Ca/Al and Sr/Al ratios. The most extensively used proxy for palaeoproductivity reconstructions, however, is Ba enrichment in marine sediments, since it has been demonstrated that Ba is a reliable indicator for variations in biological productivity when derived from authigenic marine barite originated in the water column (e.g., Dehairs et al, 1987;Bishop, 1988;Dymond et al, 1992;Van Os et al, 1994;Francois et al, 1995;Paytan et al, 1996;Martínez-Ruiz et al, 2000;Turgeon and Brumsack, 2006;Gallego-Torres et al, 2007).…”