Articles | Volume 12, issue 10
Biogeosciences, 12, 3043–3060, 2015
Biogeosciences, 12, 3043–3060, 2015

Research article 27 May 2015

Research article | 27 May 2015

Pleistocene sediment offloading and the global sulfur cycle

S. Markovic1, A. Paytan2, and U. G. Wortmann1 S. Markovic et al.
  • 1Department of Geology, University of Toronto, 22 Russell St. M5S3B1, Toronto, Canada
  • 2Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, CA 94064, USA

Abstract. Quaternary sea level fluctuations have greatly affected the sediment budgets of the continental shelves. Previous studies suggested that this caused a considerable increase in the net loss of shelf sediments. Since sediment accumulation and erosion are closely tied to the formation and re-oxidation of pyrite, we use a high-resolution record of sulfur isotope ratios (34S / 32S) of marine sulfate to evaluate the implications of the so-called "shelf sediment offloading" on the global sulfur cycle. Modeling of our δ34S record suggests that erosion during sea level lowstands was only partly compensated by increased sedimentation during times of rising sea level and sea level highstands. Furthermore, our data suggests that shelf systems reached a new equilibrium state about 700 ka, which considerably slowed or terminated shelf sediment offloading.

Short summary
We present a new Quaternary S-isotope record of seawater sulfate. We find that the steady decline in the seawater S-isotope ratios stops around 700ka, which we relate to the termination of the massive net “sediment offloading”and a new equilibrium state between shelf erosion during sea level lowstands and sediment resupply during sea level highstands.
Final-revised paper