Late Quaternary hydroclimate variability in Madagascar and its connection atmospheric circulation patterns
Description
The dataset contains bulk geochemical data (δ¹³Corg, TOC, TN and C/N), n-alkane abundances and their hydrogen isotope composition as well as percentages of pollen groups in a sediment core taken from the Central Highlands of Madagascar. The data are used to interpret past climate conditions in the tropical region of SE Africa , particularly hydrclimate changes in Madagascar, which relate to atmospheric circulation patterns. The data covers the period from 26.0000 before present to present. Data are provided in one spreadsheet (xlsx) file with four tabs containing: Bulk geochemistry data (δ¹³Corg, Total Organic Carbon (TOC), Total Nitrogen (TN), C/N ratio) against core depth and age. Leaf wax alkane abundances (C23, C25 C27, C29, C31, C33) against depth and age. Leaf wax hydrogen isotope data with standard deviations (δD17, δD19, δD21, δD23, δD25 δD27, δD29, δD31,δD33) against depth and age. Percentages of pollen group (Ericaceae, Poaceae, Cyperaceae, Other tree and shrubs, Other herbs, Ferns, Aquatic plant, Fungii, Algae) against depth and age.
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Steps to reproduce
This dataset was compiled for a study that aims to shed light of the timing and pace of Madagascar climate variability and the predominant forcing mechanisms behind this variability over the last 26000 years. The analysis was performed in a sediment core retrieved from the Ilaika Marais wetland in Antananarivo, central - eastern Madagascar (18°56'11.92"S 47°32'49.89"E). TOC, TN and δ¹³Corg were quantified with a Carlo Erba NC2500 elemental analyzer coupled with a Finnigan MAT Delta V mass spectrometer at the Stable Isotope Laboratory, Stockholm University. Total lipid extracts were obtained via sonication of freeze-dried and powdered sediment samples at the department of Geological Sciences, Stockholm University. The hydrocarbon fractions were analyzed by gas chromatography–mass spectrometry (Shimadzu-QP2010 Ultra system), for n-alkane identification and quantification. The stable hydrogen isotopic composition (deuterium/hydrogen ratio) of n-alkanes (δD) was analyzed using a Thermo gas chromatography-isotope ratio mass spectrometry (GC-IRMS) system at the department of Environmental Sciences, Stockholm University. Samples were extracted for pollen analysis and prepared according to standard methods (Moore et al., 1991; Bennett and Willis, 2001). The pollen extract was mounted in solid medium (glycerol) and counts were conducted using a light microscope at magnifications of 400× and 1000×. Identifications were facilitated using the African Pollen Database (Lezine et al., 2021). Palynomorphs were grouped into ecological units: Ericaceae (shrubs and herbs of the upper montane type), Forest trees and shrubs (of montane type), Poaceae (Grasses), Cyperaceae (Sedges), Other herbs, Aquatics, Ferns, Fungi and Algae. Counting was performed until the pollen sum (including aquatics and Cyperaceae) reached at least 200 grains (the total count ranged from 207–1293).