Geoscience Reference
In-Depth Information
Figure 3.4
Drilling a linear dune in the eastern Namib Desert, Nambia. This approach can yield many samples for OSL dating,
but limits analysis of the materials and structures within the dune itself (photo: Abi Stone).
isotopes to produce a uranium series chronology of aridity
and atmospheric temperature spanning 50 000 years.
from onshore sources have in some cases been supple-
mented by studies of land-derived pollen (see Parmenter
and Folger, 1974; Melia, 1984; Dupont
et al.
, 2000).
Terrestrial inputs are added to the relatively constant
supply of oceanic organic carbonates (Bradley, 1999).
Therefore, core sections with a relative abundance of car-
bonates indicate limited terrestrial inputs, with the inverse
relationship applying when carbonates are poorly repre-
sented. Analysis of particle size (Schroeder, 1985; Stuurt
and Lamy, 2004), mineralogy (Windom, 1975; Hashimi
and Nair, 1986), quartz grain coloration (Diester-Haass,
1976) and particle surface microrelief (Krinsley, 1978)
have been used to determine the transportation pathway
and hence palaeoenvironmental significance of the ter-
rigenous components of ocean-core sediments. Recent
studies have tended to focus on particle size variations
3.2.5
Marine sediments and palaeoaridity
Analyses of terrestrially-derived sediments in ocean cores
have contributed greatly to interpreting the timing, inten-
sity and extent of Quaternary arid zone extensions. Much
land-derived detritus reaches the oceans through fluvial
and aeolian pathways. Down-core changes in the abun-
dance of inputs from these sources provide information
on weathering and erosion processes and consequently
the hydrological regimes on shore, together with an indi-
cation of the intensity and direction of wind systems (see
Pokras and Mix, 1985; Stuut
et al.
, 2002; Holz, Stuut and
