In new research, scientists from the University of Cambridge and elsewhere reconstructed changes in summer and winter rainfall from trace elements and oxygen, carbon, and calcium isotopes of a stalagmite from Dharamjali Cave in the Himalaya spanning 4,200-3,100 years ago. They found evidence for a 230-year period of increased summer and winter drought frequency between 4,200 and 3,970 years ago, with multi-decadal aridity events centered on 4,190, 4,110, and 4,020 years ago. The record highlights the deficits in winter and summer rainfall during the urban phase of the Indus Civilization, which prompted adaptation through flexible, self-reliant, and drought-resistant agricultural strategies.
“We discover explicit confirmation that this duration was not a brief emergency but a gradual alteration of the environmental circumstances in which the Indus population resided,” said Professor Cameron Petrie, an archaeologist at the University of Cambridge.
In their research, Professor Petrie and colleagues mapped out past precipitation patterns by scrutinizing growth strata in a stalagmite procured from Dharamjali Cave adjacent to Pithoragarh, India.
By gauging various environmental markers, such as oxygen, carbon, and calcium isotopes, they acquired a representation demonstrating the corresponding rainfall during specific seasons.
Furthermore, they employed Uranium-series dating techniques of great accuracy to determine the timing and length of the arid periods.
“Numerous indications enable us to assemble the characteristics of these dry spells from different perspectives — and verify that they align,” said Dr. Alena Giesche, also from the University of Cambridge.
The study authors distinguished discrete intervals of substandard precipitation in both the summer and winter seasons.
“The proof of drought affecting both planting seasons is exceedingly meaningful for comprehending the influence of this epoch of climatic transformation on human societies,”…
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