International Geologiical Congress - Oslo 2008

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CGC-05 Fennoscandian uplift and global sea level changes

 

Sea-level record in a N-S transect, from Western Mediterranean to Eastern Atlantic Margin in last 2 Myr

 

Cari Zazo, Museo Nacional CC. Naturales, CSIC (Spain)
Jose Luis Goy, Universidad de Salamanca (Spain)
Teresa Bardaji, Universidad de Alcala (Spain)
Cristino J. Dabrio, U.C.M. (Spain)
Claude Hillaire-Marcel, UQAM (Canada)
Angel González-Delgado, Universidad de Salamanca (Spain)
Jorge Civis, Universidad de Salamanca (Spain)
Ana Cabero, Museo Nacional CC. Naturales, CSIC (Spain)
Javier Lario, UNED (Spain)
Pablo G. Silva, Universidad de Salamanca (Spain)
Vicente Soler, Estación Volcanológica de Canarias, CSIC (Spain)
Pierre Y. Gillot, UPS-IPGP, Univ. Paris Sud (France)
 

 

Several marine terrace flights were selected in a roughly N-S transect, covering different geodynamic and climatic settings from Western Mediterranean (Balearic Is. - Peninsular coasts, Spain) to Cape Verde Archipelago. Climate ranges from Mediterranean to subtropical and tropical. Geodynamic framework includes collisional plate boundary (Mediterranean sections) and volcanic Islands (Canary and Cape Verde sections), tidal range also varies from tideless to mesotidal coasts. The comparative study of all sequences was based on a detailed geomorphological mapping of marine, transitional and terrestrial deposits as well as facies analyses, petrology and palaeontology. Chronological determinations include U-Th (alpha, TIMS), 14C, K-Ar, AAR and palaeomagnetic measurements. Present elevation of marine terraces refer to mean high tide (datum=0) and altitude is given for the inner marine edge, so if we consider the paleo sea-level position at 2m asl in stable areas for the peak of MIS 5.5, and an altitude similar than present for other Pleistocene interglacials, the studied sequences developed in areas submitted to low uplifting trend (0.03 to 0.05 mm/yr).
Marine terrace heights range from 65m asl to 0m. Number of outcropping terraces is similar in the studied sequences of Cape Verde, Canary Islands and Almería (∼15 levels) showing a similar morphostratigraphic pattern. The following groups of sequences can be established: First, Early Pleistocene with a first part characterized by superposed marine deposits and fan deltas, both recording superimposed marine cycles, changing to a staircased-like arrangement during the last part of this period; Second, Middle Pleistocene sequences can also be subdivided into two subgroups separated by a major palaeocliff. In some cases, as in Balearic Islands (Mediterranean) warm "Senegalese" fauna starts to appear in the most recent terrace of the older subgroup that may also be wider than older and younger terraces. The age of this wide terrace (∼13-8m asl), difficult to state, correlates with a highstand of MIS9 or most probably MIS11, according to field and geochronological data. Third, last part of Pleistocene usually includes marine terrace from MIS5.5, outcropping at heights not exceeding 2-3m. So considering the altitudinal difference between inner edges of both terraces, the palaeo sea-level record for MIS 9 or most probably for MIS 11, never exceeded +7-9m on these coasts. Summarizing, Early Pleistocene marine terraces record small amplitude sea level oscillations that increase in the last part of the cycle, with more evident staircases during the Middle and Late Pleistocene, reflecting major amplitude of sea-level changes. A prominent sea level highstand occurred during the Middle Pleistocene, suggesting a palaeosea-level at 7-9m asl possibly during MIS 9, or more probably MIS 11. Supported by Spanish Proj. CGL/05-01336, CGL/05-04655, CGL/06-05473; IGCP-495; INQUA Comm. Coastal-Marine Proc.; GEOTOP Lab. (Can)

 

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