Mg/Ca-paleothermometry in the western Mediterranean Sea on planktonic foraminifer species Globigerina bulloides: Constraints and implications

Abstract

We generated a high-resolution SST Mg/Ca record for the surface-dwelling planktonic foraminifera Globigerina bulloides from the core MD99-2346 collected in the Gulf of Lion, and compared it to that obtained using modern analogue techniques applied to fossil foraminiferal assemblages (SST MAT). The two temperature records display similar patterns during the last 28,000 years but the SST Mg/Ca estimates are several degrees warmer ($ +4 8C) than SST MAT. The temperature shift between SST Mg/Ca and SST MAT remained relatively constant over time. This seems to exclude a bias on the Mg/Ca record associated with salinity or secondary Mg-rich calcite encrustation on the foraminiferal tests during early diagenesis. Therefore, anomalously high Mg/Ca suggests either: (1) the empirical equation for G. bulloides of Elderfield and Ganssen (2000) is incorrect; or (2) there is a specific Mediterranean genotypes of G. bulloides for which a specific Mg/Ca-temperature calibration is needed.

Sea surface temperature variations in the western Mediterranean Sea over the last 20 kyr: A dual‐organic proxy (U K′ 37 and LDI) approach

“…Gray arrows represent deepwater mass circulation: the Levantine Intermediate Water and the western Mediterranean deep water. (b) Map of the Mediterranean Sea with the position of other marine records cited in the text, wherein either organic or inorganic temperature proxies were carried out from the western to the eastern Mediterranean: ODP 976 and ODP975 [ González‐Donoso et al ., ]; 384B and 436B [ Nieto‐Moreno et al ., ]; KS8230, RL11, and ODP967 [ Emeis et al ., ]; ODP 977 [ Martrat et al ., , ; Huguet et al ., ]; MD95‐2043 [ Cacho et al ., , ; Martrat et al ., , ]; MD99‐2346 [ Melki et al ., ; Boussetta et al ., ]; KET80‐19 and KET80‐03 [ Kallel et al ., ]; BS79‐38 and BS79‐33 [ Cacho et al ., , ]; MD04‐2797 and MD84‐632 [ Essallami et al ., ; Sicre et al , ]; NU04 and GeoB10709‐04 [ Grauel et al ., ]; and GeoB7702‐3 [ Castañeda et al ., ].…”

“…Foraminiferal stable oxygen isotope compositions (δ 18 O) in core 293G were determined on G. bulloides from the fraction >125 μm. The shells were analyzed using a Finnigan MAT 252 mass spectrometer with an [Martrat et al, 2004[Martrat et al, , 2007Huguet et al, 2011]; MD95-2043 [Cacho et al, , 2002Martrat et al, 2004Martrat et al, , 2007; MD99-2346 [Melki et al, 2009;Boussetta et al, 2012]; KET80-19 and KET80-03 [Kallel et al, 1997a]; BS79-38 and BS79-33 [Cacho et al, , 2002; MD04-2797 and MD84-632 [Essallami et al, 2007;Sicre et al, 2013]; NU04 and GeoB10709-04 [Grauel et al, 2013]; and GeoB7702-3 [Castañeda et al, 2010].…”

“…More recently, a combination of U K′ 37 and TEX 86 proxies has been applied in the western and central Mediterranean to reconstruct temperatures for the last few millennia [ Grauel et al ., ; Nieto‐Moreno et al ., ] and the penultimate interglacial to glacial cycle (from 244 to 130 kyr) [ Huguet et al ., ], and in the eastern Mediterranean for the last 30 kyr [ Castañeda et al ., ]. In general, these SST reconstructions have revealed a temperature gradient between the colder western and the warmer central Mediterranean and Levantine basin, as well as a close connection of the short‐term Mediterranean climate and oceanographic variability with North Atlantic fluctuations [ Cacho et al ., , ; Martrat et al ., , ; Essallami et al ., ; Boussetta et al ., ]. We studied two marine cores from the Alboran Sea basin to (1) obtain a continuous record of SST at high resolution for the last 20 kyr, (2) to test the relevance of the novel LDI proxy in marine records from midlatitude areas, and (3) to obtain additional information about potential seasonal effects on SST records using algae‐derived organic proxies.…”

Western Mediterranean Sea Paleothermometry Over the Last Glacial Cycle Based on the Novel RI‐OH Index

“…In the Mediterranean Sea, U K′ 37 reflects November-May rather than annual SSTs (Tierney & Tingley, 2018). The Mg/Ca ratio was measured on Globigerina bulloides at the sites selected for this regional comparison (Boussetta et al, 2012;Jiménez-Amat & Zahn, 2015). Microfossil-based anomalies do not all correspond to annual SST (see Table 1 and supporting information Data Set S2 for further information).…”

Genesis and Evolution of A Beach-Ridge Plain Reflecting Relative Sea-Level Rise: A Case Study From Trab El Makhadha Gulf of Gabes, Southeastern Tunisia

“…Significant increases in precipitation, river discharge, and sediment supply occurred in the Mediterranean Sea between about 9000 to 4500 14 C years B.P. (Kallel et al 1997;Essallami et al 2007;Boussetta et al 2013). The optimum of wet conditions coincided with the deposition of the last sapropel (centimetric organic-rich layer) in the eastern Mediterranean basin, centered at around 8500 14 C years B.P.…”