Subaquatic Dust Deposits - Mineral Dust: A Key Player in the Earth System - page 436

17.1 Introduction

Another archive of dust deposits, next to the well-studied on-land - loess - deposits
(Chap. 16 ) , is dust archives that are found in lacustrine and marine settings. In this
chapter, the great potential of these “underwater” dust deposits as an archive for past
environmental conditions is explored.
Through geologic time, rivers, icebergs and winds transport sediments from
land to the ocean floor as well as to lake floors. On these lake and ocean
floors, there are places where sedimentary archives can be found that record
continuous accumulation of these land-derived sediments and which are undisturbed
by syndepositional changes (e.g. lobe switching in delta fans) and post-depositional
changes (e.g. bottom-current winnowing and re-deposition in gravity flows and
bioturbation). Usually, these undisturbed deposits are in the distal (several hundred
kilometres) offshore parts of lakes and oceans.
Figure 17.1 shows a map of all recordings of dust records in the DIRTMAP
2( D ust I ndicators and R ecords of T errestrial and MA rine P alaeoenvironments)
database, including on-land (loess) and ice-core deposits. Clearly, marine sites
dominate the map, and most of the terrestrial records comprise loess deposits.
Unfortunately, hardly any lacustrine records are present in this compilation. The
map clearly shows that the marine dust records are concentrated around the mid-
latitude deserts, mainly offshore either sides of northern Africa in the Atlantic and
Indian Oceans, respectively, as well as in the western North Pacific offshore the
major Asian deserts.

Fig. 17.1 Map of marine, terrestrial (loess deposits, peat bogs and lakes) and ice-core sites
contained within the DIRTMAP 2 database. http://www.bridge.bris.ac.uk/projects/DIRTMAP .
Note: DIRTMAP 3 is currently being compiled