Provenance study of endokarst fine sediments through mineralogical and geochemical data (Lezetxiki II cave, northern Iberia)

The characteristics and provenance of the fine sediment forming the matrix of detrital endokarst fill can vary greatly, and their study provides valuable information about the paleoenvironment and the different sedimentary and diagenetic processes in which it was formed and deposited. This paper applies this study to the case of Lezetxiki II cave (Arrasate, Gipuzkoa). Using X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM–EDS) analysis with samples of endokarst sediment, rocks and soils in the surroundings of the cave, the following source areas and sedimentary processes have been identified: 1) allochthonous sedimentation through the fluviokarst processes which eroded soils formed on siliciclastic formations. It is characterised by a high percentage of illite in the sediment and predominated in relatively cold periods in MIS 6 and MIS 2–4; 2) sedimentation through infiltration from karst fissures of the autochthonous soils formed on the limestone substrate (terra rossa). It is characterised by a higher vermiculite content, and prevailed in the warm MIS 5 period and the Holocene; 3) chemical sedimentation, where calcite precipitated in the form of speleothems in warmer and more humid periods; and 4) deposition of microfauna bones in owl pellets.