DOI: 10.25921/p2gg-ej75
title: NOAA/WDS Paleoclimatology - Goda Mea Cave Geochemical Data from 129200 to 108200 Cal Yr BP

description: Oxygen and carbon (δ18Ο/δ13C) isotope, growth rate and trace element data are reported for a U-Th dated, annually-laminated stalagmite, GM1 from Goda Mea Cave, Ethiopia. The stalagmite grew intermittently around the last interglacial. The proxy records are used to develop a conceptual growth model of the stalagmite and to assess its potential for revealing a climate signal in this climatically sensitive northeastern African region during an important period in the evolution of Homo sapiens and dispersal of Anatomically Modern Humans out of Africa. Speleothem deposition is of short-duration occurring at ∼129 ka, ∼120 ka, in an undated growth phase, and at ∼108 ka; probably due to tectonic activity. δ18Ο composition is very stable within growth phases (1σ variability < 0.76‰), as are Mg/Ca, Sr/Ca and Ba/Ca, all indicative of well-mixed source-waters. A shift to positive δ18Ο values and increased variability in Mg/Ca, Sr/Ca and Ba/Ca prior to growth hiatuses is observed, indicating a loss of the well-mixed water source prior to growth cessation. Mean δ18Ο composition (−3.82 to −7.77‰) is lower than published modern and Holocene stalagmites from the region. Geochemical data, statistical analyses, and a conceptual model of stalagmite growth, demonstrate that climatic conditions recorded by GM1 were wetter than the Holocene. The ∼129 ka growth phase particularly presents an annual record of the relative Intertropical Convergence Zone (ITCZ) position. The GM1 record, the oldest high-resolution continental climate record from Ethiopia so far published, presents evidence that any early human migrations which occurred during MIS 5 are likely to have occurred during a wet event in northeast Africa.
description: Data contributed as part of SISAL v3 Global Speleothem Isotope and Trace Element Database (https://doi.org/10.25921/jajq-qg60). Notes from the SISAL database: Mixed Geology: the hostrock above the cave consists of a 25m thick layer of sandy limestone intercalated with some marl and mudstone, above this layer there is another 20m of calcareous sandstone, silt, carbonate rich shale and marl. \\ GM1 (SISAL entity_id = 764) For this specific speleothem it is unknown whether the drip water and modern calcite are in equilibrium, but in other places in this region most drips and modern calcite are not in equilibrium. Mixed age model: U series ages and lamina counting combined. Modern Reference for lamina counting is the year of U-Th chemistry as the lamina counts were anchored using U-Th dates. Annual lamination is based on comparison of the lamination to other speleothems from the same region - in these other speleothems similar lamination has been shown to be annual by radiometric dating. GM1 laminae are similar in thickness and appearance to those other speleothems. Examination of thick sections of GM1at various levels of the growth phases (Fig. 2) showcontinuous and regular visible laminaewith alternating brownish calcite (Dark Compact Laminae, DCL) and thinner white calcite (White Porous Laminae,WPL) as defined by Genty and Quinif (1996) and Genty et al. (1997). The presence of fine sediments on the white porous calcite, and some dissolution features at the top of the DCL, suggests some seasonal infiltration variability (cf. Borsato et al., 2007). Overall, the regularly alternating DCL/WPL laminae sequence, even without more obvious structures from infiltration variability, indicate deposition under a seasonal hydroclimate regime (e.g. changes in dripwater supersaturation or cave air CO2 concentration), where recharge was sufficient to maintain continuous dripping to the stalagmite. Sample data: the stable isotope and trace element analyses were done on powder aliquots that were separately drilled, however data with the same interpolated age (interp_age) were combined together using the depth value of the stable isotope analysis in the original dataset.