Articles | Volume 5, issue 4
Earth Surf. Dynam., 5, 781–789, 2017
Earth Surf. Dynam., 5, 781–789, 2017

Short communication 01 Dec 2017

Short communication | 01 Dec 2017

Short communication: Massive erosion in monsoonal central India linked to late Holocene land cover degradation

Liviu Giosan1, Camilo Ponton1,2,a, Muhammed Usman3, Jerzy Blusztajn1, Dorian Q. Fuller4, Valier Galy5, Negar Haghipour3, Joel E. Johnson6, Cameron McIntyre3,7,b, Lukas Wacker7, and Timothy I. Eglinton3,5 Liviu Giosan et al.
  • 1Geology & Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
  • 2MIT/WHOI Joint Program in Oceanography/Applied Ocean Science and Engineering, Cambridge, MA, USA
  • 3Geological Institute, ETH Zurich, 8092 Zurich, Switzerland
  • 4Institute of Archaeology, University College London, London, UK
  • 5Marine Chemistry & Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
  • 6Earth Sciences, University of New Hampshire, Durham, NH, USA
  • 7Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zurich, Switzerland
  • anow at: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
  • bnow at: Scottish Universities Environmental Research Center, E. Kilbride, G75 0QF, UK

Abstract. Soil erosion plays a crucial role in transferring sediment and carbon from land to sea, yet little is known about the rhythm and rates of soil erosion prior to the most recent few centuries. Here we reconstruct a Holocene erosional history from central India, as integrated by the Godavari River in a sediment core from the Bay of Bengal. We quantify terrigenous fluxes, fingerprint sources for the lithogenic fraction and assess the age of the exported terrigenous carbon. Taken together, our data show that the monsoon decline in the late Holocene significantly increased soil erosion and the age of exported organic carbon. This acceleration of natural erosion was later exacerbated by the Neolithic adoption and Iron Age extensification of agriculture on the Deccan Plateau. Despite a constantly elevated sea level since the middle Holocene, this erosion acceleration led to a rapid growth of the continental margin. We conclude that in monsoon conditions aridity boosts rather than suppresses sediment and carbon export, acting as a monsoon erosional pump modulated by land cover conditions.

Short summary
A reconstruction of erosion in the core monsoon zone of India provides unintuitive but fundamental insights: in contrast to semiarid regions that experience enhanced erosion during erratic rain events, the monsoon is annual and acts as a veritable erosional pump accelerating when the land cover is minimal. The existence of such a monsoon erosional pump promises to reconcile conflicting views on the land–sea sediment and carbon transfer as well as the monsoon evolution on longer timescales.