D P [‰ VSMOW]
Rain amount [mm month -1 ]
Fig. 1 a Satellite image with position of surface sediments and respective compound-speci c
composition of n-C 31 alkanes (image: NASA Earth Observations), b
D composition of
precipitation as simulated by ECHAM5-wiso T63 simulation (nudged mode, simulated period
1982), c Average NW African climate in January; black arrows display major wind
directions, green line denotes position of the Intertropical Convergence Zone (ITCZ), red dot marks
the position of GeoB9501-4, green dot marks the position of GeoB7920-2, d same as c in July
by a strong bio-geophysical climate-vegetation feedback. The slow decline in
orbital-paced North African summer insolation during the Holocene might have led
to a sudden, i.e., within centuries, deserti
cation of the Sahara in the mid-Holocene
(e.g., Claussen 2009 ). This hypothesis is supported by a rapid increase of dust
export at around 5,500 years BP detected offshore NW Africa (deMenocal et al.
2000 ). A contrasting hypothesis suggests a continuous southward retreat of mon-
soonal rainfall due to insolation decline causing gradual environmental deteriora-
tion (e.g., Kr
pelin et al. 2008 ).
To provide more insights into the paleo-hydrologic evolution of NW Africa over
the Holocene and unravel past climate and vegetation changes, we conducted a
combined data-modeling study.
D compositions of terrigenous plant lipids, pro-
viding direct insights into continental hydrologic changes (Sachse et al. 2012 ), were