Browsing by Author "Jimenez-Espejo, Francisco J."
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- Sea-level and monsoonal control on the Maldives carbonate platform (Indian Ocean) over the last 1.3 million yearsPublication . Alonso-Garcia, Montserrat; Reolid, Jesus; Jimenez-Espejo, Francisco J.; Bialik, Or M.; Alvarez Zarikian, Carlos A.; Laya, Juan Carlos; Carrasquiera, Igor; Jovane, Luigi; Reijmer, John J. G.; Eberli, Gregor P.; Betzler, ChristianThe Maldives Archipelago (Indian Ocean), composed of two rows of atolls that enclose an inner sea, offers an excellent study site to explore the forcings of carbonate production at platforms. Glacial-interglacial sea-level changes have been claimed to be the main factor controlling the carbonate platform factories; however, climatic factors may also have an impact. In this work we used geochemical compositional records, obtained by X-ray fluorescence (XRF) core-scanning from the International Ocean Discovery Program (IODP) Site U1467 in the Maldives Inner Sea, to analyze the orbitally driven fluctuations on the carbonate production and export from the neritic environment into the Maldives Inner Sea over the last 1.3 million years.High Sr aragonite-rich carbonates (HSAC) from neritic settings were deposited in the Maldives Inner Sea during sea-level highstand intervals, increasing the Sr / Ca values. In contrast, low Sr / Ca values are observed coincident with sea-level lowstand periods, suggesting that large areas of the atolls were exposed or unable to grow, and therefore, there was a demise in the carbonate production and sediment export to the Maldives Inner Sea. However, comparison of the Sr / Ca values and the sea-level reconstructions for different interglacial periods before and after the mid-Brunhes event (MBE, similar to 430 ka ) indicates that sea level is not the only factor controlling the production of HSAC during sea-level highstands. The study of monsoon and primary productivity proxies ( Fe -normalized, Fe / K , and Br -normalized records) from the same site suggests that the intensity of the summer monsoon and the Indian Ocean dipole probably modulated the carbonate production at the atolls. Moreover, Marine Isotope Stage 11 stands out as a period with high sea level and extraordinary carbonate production in the Maldives platform. This outstanding carbonate production in the Maldives atolls (and in other low-latitude carbonate platforms) probably contributed to the mid-Brunhes dissolution event through a strong shelf-to-basin fractionation of carbonate deposition.
- Shellfish collection on the westernmost Mediterranean, Bajondillo cave (similar to 160-35 cal kyr BP): A case of behavioral convergence?Publication . Cortés Sánchez, Miguel; Simon-Vallejo, Maria D.; Jimenez-Espejo, Francisco J.; Lozano Francisco, Maria del Carmen; Luis Vera-Pelaez, Jose; Maestro Gonzalez, Adolfo; Morales-Muniz, ArturoThe Middle (MP) and Early Upper Paleolithic (EUP) evidences of shellfish collection on the southern Iberian site of Bajondillo cave are presented and compared with Westernmost Mediterranean archaeological sites. The main feature is stasis for Mytilus galloprovincialis represents the dominant taxon during a similar to 120kyr temporal sequence. The second feature is the decrease of the shellfishing signal when site distance to the coast increases. The data reveal that shellfish collection was practiced during Marine Isotopic Stage 4, a poorly documented stage in terms of aquatic adaptations. Striking is also that mollusc assemblages evidence an uninterrupted decreasing trend in terms of remains from the earliest to the latest levels, in particular when H. sapiens replaced H. neanderthalensis. Although taxa of secondary importance are too scarce to make reliable inferences, another difference between the MP and EUP collections is the substantial increase of infaunal bivalves in the latter cultural period. Warm and cold water mollusc records match temperature rises and drops although the scarcity of data do not allow one to proceed beyond qualitative statements. Likewise, the prevalence of fresh and brackish water mollusc hint at a permanent presence of freshwater around the site at all times. When compared with assemblages from the Alboran sea region (Westernmost Mediterranean Sea), the Bajondillo cave collections are remarkable for their abundance of mussels. Comparison between Bajondillo cave and Pinnacle Point reveal that infaunal bivalve abundances in the South African site are far higher than those recorded in the MP levels, though not those from the EUP. Whether this feature hints at subtle differences existing between the collection of shellfish by H. sapiens and H. neanderthalensis, reflects a behavioral convergence between the two hominine lineages or represents an inherited cognitive trait from a common ancestor is an issue in need of further analysis. (C) 2019 Elsevier Ltd. All rights reserved.