Depositional histories of vegetation and rainfall intensity in Sierra Madre Oriental Mountains (northeast Mexico) since the late Last Glacial

Abstract

An evaporite enriched sediment archive from the dry Sandia Basin located in the water-stressed western foothills of the Sierra Madre Oriental Mountains (northeast Mexico) was studied to reconstruct depositional histories of vegetation and rainfall intensity in orbital to millennial-scales over the last ~32.5 cal ka. Surrounding vegetation had more C3 plants during the late last glacial and deglaciation and the expansion of more drought tolerant C4 plants occurred only after ~5 cal ka BP. Clastic minerals were sourced from different lithologies within the watershed and their abundances helped to infer runoff dynamics and hence the rainfall intensities. Deposition of more mixed-layer clay represented wetter intervals over the late last glacial and deglaciation. Transportation of clastics from the nearby lithology during these wetter intervals suggested that high-intensity rainfall events were less frequent. Response to the Heinrich stadials (H3, H2 and early H1) was mainly similar (drier) and erosion in the watershed remained less-than-average. Transportation of more quartz-rich sediments from distal lithologies during the late Bølling-Allerød (B/A) interstadial and between ~6.2 and 4 cal ka BP with a depositional hiatus between ~12.7 and 6.2 cal ka BP represented the intervals of more frequent high-intensity rainfall events, possibly related to short-lived storms. We hypothesize that the Gulf of Mexico sea surface temperature was a principal forcing. Total annual precipitation in this region decreased but the frequency of short-lived storms increased during the warmer Atlantic Multidecadal Oscillation (AMO) states. Warmer conditions also led to deposition of more gypsum. Our observation, however, needs further evaluation under the modern-day greenhouse warming scenario.