Djara Cave in the Western Desert of Egypt: Morphology and evidence of Quaternary climatic change

With stalactites, columns, stalagmites and flowstones up to 6m high and 1.5m in diameter, Djara Cave in the Western Desert is one of very few well-decorated caves in Egypt. U-series ages for four speleothems (140 ± 16, 201 ± 2/233 ± 24, 221 ± 34, and 283 ± 56ka) suggest humid intervals during marine isotope stages 5 and 7, and possibly also during stage 9. Importantly, none of the secondary carbonates date to the Holocene, despite archaeological evidence both in the cave, and on the ground surface above it, of visits to the site by ancient peoples, and of a more humid period of climate from about 11.5 to 6.5ka. δ¹⁸O of speleothem carbonate averaged -12.1‰ PDB, indicating deposition by meteoric waters significantly depleted in ¹⁸O. Using ¹⁸O PDB of speleothem carbonate, and ¹⁸O SMOW of ancient groundwater in the Nubian aquifer, the mean annual temperature at the time of speleothem deposition is estimated to have been 23.1°C, which is 1°C above the present mean annual temperature at the Farafra and Baharya oases. In Israel and Oman, modern speleothem carbonate is less depleted in ¹⁸O than Holocene-age material, and this in turn is less depleted than carbonate deposited during isotope stage 5. This suggests that in these areas the Holocene was wetter than the present but not as wet as during marine isotope stage 5. At Djara Cave, the absence of speleothem deposits of Holocene age also suggests that this period was not as wet as during earlier interglacials. The ¹⁸O-depleted waters from which the Djara speleothems were deposited appear to have originated in air masses that crossed North Africa from west to east at a time when there was a more southerly westerly airflow than now.