Estudio de paleotemperaturas en el Mar de Alborán entre 250 y 150 ka utilizando la técnica de los análogos modernos

Résumé

Planktonic foraminifers from core ODP site 977a have been studied to estimate sea surface temperatures (SST) in the Alboran Sea between 245 and 145 kyr. Similar studies have been performed in this basin but only for the last 150 kyr (Perez-Folgado et al., 2004). SSTs in this basin are highly controlled by the atlantic superficial incoming flux through the Gibraltar Strait. In this study we estimate paleotemperatures with the modern analog technique which consists on a comparison between core and modern sample assemblages. This method assumes that similar planktonic foraminifer assemblages develop under the same ecological conditions and that foraminifer ecological preferences have not changed in time. This technique also provides a dissimilarity index (between 0 and 1) which depends on the liability of the estimation obtained. In this study we used Kallel et al. (1997) modern database which contains a total of 253 samples, 123 from the North Atlantic and 130 from the Mediterranean Sea. For the estimations we used PaleoAnalogs 2.0, computer program developed by the University of Salamanca (Theron et al., 2004). A small SST difference exists between substages 7.3, 7.2 and 7.1. Important millennial cyclicities (7.4, 5.6 and 4.6 kyr) occur during the whole studied period, both in warm and cold intervals, although changes seem to be broader during cold ones. Seasonality is higher during the warmer substages, 7.5 and 7.3, whereas it is smaller during the strong Northern Hemisphere summer insolation minimum in substage 7.4.