Abstract: Short Term Climatic Fluctuations in Africa
and Asia During
Holocene — Review and Possible Causes.
PRASAD, SUSHMA and S.K. GUPTA, Physical Research Laboratory, Post Box No. 4218, Navrangpura, Ahmedabad, 380009, India.
A growing database for Holocene palaeoclimate from Asia and
Africa
is increasingly indicative of the not so synchronous nature
of climatic changes in different regions and the presence of short
term climatic fluctuations which cannot be directly attributed to
changes in orbital parameters that seem to explain the long term
Quaternary palaeoclimatic changes. This study attempts to document
the nature, timing and extent of these short lived events during
Holocene, superimposed on the broader climatic trends in Asia and
Africa
. Our studies indicate that (i) there may not be a major
difference in the timing of onset of early Holocene wet phase in
the African-Asian region. The limited data set that is presently
available from S.
Africa
only points to a slightly later onset of
Holocene optimum, (ii) there does not seem to be enough evidence to
indicate a systematic gradual onset of monsoon following the
northward progression of the Inter Tropical Convergence Zone
(ITCZ), (iii) a dry episode at ~7 ka previously documented from
Africa
has been found to be far more widespread and also reported
from India, Tibet, China and off the coast of Arabia. Other
episodes of short term wet and dry phases during mid to late
Holocene, in the African-Asian region, have also been found, (iv)
there seems to be a difference in the record and timing of short
term climatic changes from closely spaced locations, probably due
to varying sensitivity of these sites which governs their response
to climatic changes, (v) the time of onset of late Holocene arid
try ranges from 6-3 ka BP.
Some of these events had earlier been explained as being due to
gradual migration of ITCZ, variations in glacier cover and/or input
of cold water pulses resulting from melting of ice. We have
attempted to examine these hypotheses keeping in view the recently
available high resolution palaeoclimatic data from Asia and Africa
.
The results of these studies will be presented.
AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah