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Algarve: a study case for global vs regional climatic changes in mid latitude estuaries during the Holocene
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Advisor(s)
Abstract(s)
Located at the extreme southwestern end of the Iberian Peninsula, in the South of Portugal, the Algarve province is
bordered to the north by the Alentejo province, to the east by the Guadiana River, and to the west and south by the
Atlantic Ocean. Its coastal region can be divided into two different sectors: the eastern sector, which is mainly made of
barrier island and lagoon system named the Ria Formosa, and the western sector mainly represented by clastic and
carbonated cliffs. In each sector, we sampled long and short sedimentary cores (ca. 30m and 3m, respectively) in two
different estuaries. Therefore, the different sedimentary records obtained from the four estuaries should permit to identify
global vs. west-eastern regional climatic changes through the observation of several proxies. Two of these proxies are
sediment color and magnetic susceptibility, which have been acquired every five centimeters along core depth, using the
Colortron II spectrophotometer and SM-20 magneto-susceptometer, respectively. Sediment surfaces of short cores were
also digitized using the Mustek 1200 A3 PRO Scanner. Furthermore, short cores have been sampled every five centimeters
along depth in order to analyze the sediment for its major and minor elements content, its organic carbon content, and its
granulometry and mineralogy. Some shell fragments have also been sampled and sent for radiocarbon radiometry or AMS
dating, allowing therefore constructing some absolute chronologies for the several cores. Some relative chronologies based
on digital color profiles are also being used in order to correlate sedimentary sequences between cores. All the cores are
mainly composed of clay, with the existence of soil horizons at the top of the cores and frequent sand layers towards their
base. Several element profiles along depths are compared, namely those regarding Sr, Ca, F, Ba, Al and Ti, as well as
their ratios. First results indicate that geochemical and color data allow to identify similar sequences from west to east
probably related to major climate episodes. Although, pronounced differences in mineralogy and accumulation rates from
on site to another are probably due to differences, respectively, in the geochemistry of the drainage basin substratum and
in the flow rate of the rivers, and therefore to local precipitation. We acknowledge FEDER and OE that financed this study
through the Portuguese Foundation for Science and Technology (FCT) (POCTI/CTA/39733/2001).
Description
Keywords
Estuarian sediment Spectrophotometry Geochemistry Holocene
Citation
Veiga-Pires, Cristina Carvalho; Mestre, Nélia; Moura, Delminda; Joaquim Luis; Boski, T.ALGARVE: A STUDY CASE FOR GLOBAL VS REGIONAL CLIMATIC CHANGES IN MID LATITUDE ESTUARIES DURING THE HOLOCENE, Trabalho apresentado em 32nd IGC- Florence, In 32nd IGC- Florence, Florence, Italy, 2004.