Holocene climate and environmental variability based on benthic foraminifera and sediments from the inner shelf of the southeastern Mediterranean Sea
Abstract
Deep-sea sedimentary successions are generally the best marine records for reconstruction of climate variability. Nearshore successions should be more suitable as they respond better to changes in fluvial input more directly linked to climate. We present here a high resolution study of two excellently preserved ∼7 m long vibrocores taken at 33 and 37 m water depth off the southern and central parts of the Israeli coast, distally located relative to the delta of the Nile River. Unlike the deep sea record, these successions directly record aspects of Nile discharge history tracking climate variability of east equatorial and NE Africa. Sand fraction, carbonate content, and benthic foraminiferal assemblages form the database for recording the environmental changes in these shallow water sediments, dated by AMS 14C. Findings show that during the Holocene, two different climatic regimes predominated, separated by a transitional period of ∼1000 y. Between 8.4 and 6.3-6.7 kyBP the climate was relatively humid with small seasonal fluctuations. From 6.3-6.7 to 5.5 kyBP the climate regime changed from humid to semi-arid, a transition apparently accompanied by increased periodic storm activity in the eastern Mediterranean. From 5.5 kyBP to the present, the climate become drier and seasonality was more pronounced. Sedimentation rates during the early Holocene were high, exceeding 140 cm/1000 y, indicating enhanced hydrological activity in the southeastern Mediterranean and at the headwaters of the Nile River. During the late Holocene, sedimentation rates decreased drastically to below 60 cm/1000 y, reflecting reduced hydrological activity and increasing aridity in the region. The benthic foraminiferal record shows at first high abundance, diversity and equitability, suggesting that nutrient flux and concomitant productivity was higher during the early Holocene with relatively stable food supply to the sediment. This assemblage was almost entirely replaced at 5.5 kyBP by a low diversity assemblage of opportunistic species with low equitability, indicating that the environments were unstable, nutrient input was low and intermittent, and seasonality more pronounced. Furthermore, about 10 cycles of alternation between two dominant species over the last 5,500 years may correlate with historical and geological records of Nile River discharge variability.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....9499T