NOAA/WDS Paleoclimatology - Anjohibe Geochemical Data from 1700 to -64 Cal Yr BP

The environmental impact of the early human inhabitants of Madagascar remains heavily debated. We present results from a study using two stalagmites collected from Anjohibe Cave in northwestern Madagascar to investigate the paleoecology and paleoclimate of northwestern Madagascar over the past 1800 years. Carbon stable isotopic data indicate a rapid, complete transformation from a flora dominated by C3 plants to a C4 grassland system. This transformation is well replicated in both stalagmites, occurred at 890 CE and was completed within one century. We infer that the change was the result of a dramatic increase in the use of fire to promote the growth of grass for cattle fodder. Further, stalagmite oxygen isotope ratios show no significant variation across the carbon isotope excursion, demonstrating that the landscape transformation was not related to changes in precipitation. Our study illustrates the profound impact early inhabitants had on the environment, and implies that forest loss was one trigger of megafaunal extinction. Data contributed as part of SISAL v3 Global Speleothem Isotope and Trace Element Database (doi.org). Notes from the SISAL database: Geology: Limestone near the base of the karst grading upwards into dolomite. A lower resolution record from stalagmite AB2 was published in Burns et al., 2016 but was superseded by Scroxton et al., 2017 - including an enhanced age model. \\ Entity AB2, AB3 (SISAL entity_id = 188, 187): Data shown in paper and online at NOAA are either raw values or corrected to aragonite. Data deposited in SISAL has been corrected to calcite, by the original author, to facilitate comparisons. Conversion made using -0.7 for d18O and -2.5 for d13C for 100% aragonite to calcite. \\ AB2 (entity_id = 188): Mixed mineralogy has been converted as a proportion of the mineralogies present, measured by XRD and XRF: 29% calcite between 90.5 (sample_id = 388296) and 105.1mm (sample_id = 388360) and 24% calcite between 1029.2 (sample_id = 388918) and 1096.2mm (sample_id = 388947).\\ Entity ABC-1(entity_id = 738): Dating material: aragonite vs. calcite was determined uding Mg/Ca and Sr/Ca ratios (higher Mg/Ca=calcite, higher Sr/Ca=aragonite), the date at 21.5mm depth is close to the boundary between the two, trace element analyses were not continued to the base of the sample where the age at 62mm depth was measured.