Timescales of sediment transport
The importance of lateral transport for shaping the sedimentary record is widely recognized and is known to be an increasingly critical point when studying past climate conditions using proxy records of deep sea sediments. Many sites in the world ocean show signs of sediment redistribution, focusing and winnowing. Transport following re-suspension events is an important mode of delivery of organic matter to the deep ocean and across continental margins, and this process may result in significant radiocarbon age offsets between sedimentary constituents residing in different grain size fractions. The relative contribution and absolute age of the advected sediment portion as well as the duration of these transport processes and the timing of sediment re-suspension events needs to be studied. Terrigenous organic matter deposited in the ocean is also affected by transport. Different modes of delivery include dust input and river runoff. It has been shown that organic components in dust may also be up to several thousand years old, implying significant residence times in soils.
In this project we investigate timescales of transport processes of marine and terrigenous biomarkers: their residence times in intermediate reservoirs, their transit times across continental shelves and the timescales of re-distribution in the deep sea.
This study includes the analysis of deep sea sediments. For the paleoceanographic identification of lateral sediment transport and redistribution down-core samples are used. For the process-oriented study of terrigenous organic matter transferred to and re-distributed in marine sediments, core top sediments are investigated. Study areas include the Eastern Equatorial Pacific and the Black Sea.
The methodology encompasses the analysis of the radiocarbon contents of molecular fossils (biomarkers) including alkenones, n-alkanes, n-fatty acids, GDGTs as well as chloro- and pheopigments in comparison to each other but also compared to calcareous microfossils (e.g. foraminifera, bivalves) and total organic carbon (TOC). For the purification of the single biomarkers wet chemical techniques, PCGC and HPLC/MS or HPLC/DAD are applied.
Timescales of sediment redistribution affecting marine biomarkers
Comparison of compound-specific radiocarbon ages of alkenones with those of planktic foraminifera and total organic matter in the Panama Basin - an area in which the occurrence of sediment redistribution is discussed controversially.
Timescales of transport of terrigenous biomarkers
Poster presented at EGU General Assembly 2009