Changes in the deposition of terrestrial organic matter on the Laptev Sea shelf during the Holocene: evidence from stable carbon isotopes

Stable carbon isotope ratios in the organic fraction of surface sediments f rom the Laptev Sea shelf were analyzed in order to study the modern distrib ution pattern of terrestrial organic matter. The delta C-13 signature of th e surface sediments range from -26.6 parts per thousand near the coastal ma rgin to -22.8 parts per thousand in the north towards the outer shelf. Char acterizing the possible sources of organic matter by their delta C-13(org) signature reveals that the terrestrial influence reaches further north in t he eastern than in the western Laptev Sea. Downcore records of the delta C- 13(org), measured on three AMS C-14-dated cores from water depths between 4 6 and 77 m, specify the spatial and temporal changes in the deposition of t errestrial organic matter on the Laptev Sea shelf during the past 12.7 ka. The major depositional changes of terrestrial organic matter occurred betwe en 11 and 7 ka and comprised the main phase of the southward retreat of the coastline and of the river depocenters due to the postglacial sea level ri se.