Geochemical and sedimentary constraints on the formation of the Venta Micena early Pleistocene site (Guadix-Baza Basin, Spain)

Alejandro Granados,Jordi Ibáñez-Insa,Juan Manuel Jiménez-Arenas,Oriol Oms,Pere Anadón,Anu Kaakinen

doi:10.1038/s41598-021-01711-7

Abstract

Despite the paleontological relevance of the terrestrial Early Pleistocene Venta Micena bonebed (Baza Basin, Spain), it lacks a comprehensive geochemical/sedimentological study. Here, we demonstrate that the 1.5-m-thick Venta Micena limestone formed in a relatively small freshwater wetland/pond located at the periphery of the large saline Baza paleolake. Two microfacies are observed, with high and low contents of invertebrate fossils, and which originated in the centre and margin of the wetland, respectively. X-ray diffraction (XRD) mineralogy and paleohydrological characterization based on ostracod and bulk-rock geochemistry (δ13C and δ18O) indicate that the limestone reflects a general lowstand of the Baza lake, permitting the differentiation of freshwater wetlands that were fed by adjacent sources. Conversely, during highstands, the Baza lake flooded the Venta Micena area and the freshwater fauna was replaced by a saline one. Bulk-rock isotopic data indicate that the lower interval C1 of the limestone (bone-rich in marginal settings) displays general negative values, while the upper interval C2 (bone free) displays less negative values. The bones of predated mammals accumulated in the marginal areas, which were flooded and buried by recurring water-table fluctuations. Lake dynamics played a critical role in bone accumulation, which was previously considered as representing a hyena den.

Highlights

The Venta Micena (VM) paleontological site is a reference locality for Eurasian land mammal biostratigraphy at the Early-Middle Pleistocene transition from Eurasia[1,2,3]
X-ray diffraction (XRD) data were obtained from the lower section VM1 and from section VM4
VM limestone (C1 and C2) is very rich in low-Mg calcite, with values being between 70% and almost 100%

Summary

Introduction

The Venta Micena (VM) paleontological site is a reference locality for Eurasian land mammal biostratigraphy at the Early-Middle Pleistocene transition from Eurasia[1,2,3]. The youngest part of the Early Pleistocene interval of this transition is well dated in the paleolake succession of the Guadix-Baza basin (Fig. 1) with combined magnetobiochronology[4,5]. It encompasses the arrival of the first Homo genus in Europe at the nearby sites of Fuente Nueva 3 and Barranco León, the latter dated at 1.46 Ma6,7. The Guadix-Baza intramontane basin is located in the Betic Chain, at the contact between the internal and external units (Paleozoic to Triassic basement and external Mesozoic cover, respectively, see Fig. 1a). The Baza Fm has a maximum thickness of over 100 m and is widely known for hosting Plio-Pleistocene mammalian s ites[1,3]

Results

Discussion

Conclusion