Extending the Record: South American Summer Monsoon Variability During MIS 6 and a First Look into MIS 7 Using Stable Isotopes of Peruvian Speleothems

Tropical South American speleothems offer the possibility of extending paleoclimate records beyond those recorded in high latitude proxies and expose the response of lower latitudes to high latitude climate forcings. The current record of speleothems that record South American Monsoon variability in the d¹⁸O values of their calcite extends through the penultimate glacial period (MIS 6). Here, I present the results of a study that used two speleothems from Huagapo Cave, Peru to replicate the existing published d¹⁸O record from MIS 6 and extend the record into the interglacial that preceded it (MIS 7) producing a total age range of ~156,000 – 227,000 yr BP. During the penultimate glacial period the speleothems show remarkable agreement with both the published record and insolation. The d¹⁸O trend deviates from insolation during MIS 7 while d¹³C maintains a close match with insolation, suggesting the possibility of a different factor dominating the d¹⁸O record during the interglacial. A 31 kyr hiatus in speleothem growth coincides with nearby paleolimnological evidence of a dry period and glacial retreat across the transition from MIS 7 to MIS 6. The successful replication of the existing MIS 6 speleothem d¹⁸O record adds confidence to the interpretation of speleothem d¹⁸O indicating SASM intensity controlled by insolation and to the interpretation of the new MIS 7 record present in the same speleothem. The deviation from the expected relationship with insolation in part of this record indicates that the d¹⁸O signal in Andean speleothems may record local hydrological effects in addition to the amount of rainout upstream during monsoons.