Quaternary marine terraces on Sal Island (Cape Verde archipelago)

Abstract

The Quaternary sedimentary record of Sal Island includes marine and related aeolian and alluvial fan deposits. The substratum of the island is volcanic, with ages between 25 and 0.6 Ma. Quaternary marine units generally occur as raised marine terraces forming a broad staircase between elevations of 55-60 m and present sea level. Terraces include a basal conglomerate overlaid by calcarenite; both host corals, algae and molluscs.A chronostratigraphic framework for the Middle Pleistocene to Holocene units has been generated based on a geomorphologic map of the Quaternary landforms and associated deposits and morphosedimentary analysis, with support of laboratory dating: U-series by TIMS in corals, 14 C analyses, palaeomagnetic measurements, and K/Ar ages from other literature. U-series dating of corals from marine terraces provides benchmarks for the Last Interglacial (Oxygen Isotope Substage 5e) and Holocene deposits. The present elevation of the marine terraces and their staircase arrangement suggest a change in vertical movement trend around 330 ka from an uplift to either subsidence or stabilization. r

Sea level changes during the last and present interglacials in Sal Island (Cape Verde archipelago)

“…2 and 3) reaching maximum elevations of about 2 masl.ln contrast, rocky coasts with more intense wave dynamics and a steep upper shoreface form the northern half of Sal Island, to the north of the Palmeira-Pedra Lume lineation. Here, the deposits interpreted as last interglacial occur as scattered patches, some of which rise up to 5 to 6 masl (Zazo et al, 2007).…”

“…For the African coasts, faunal identifications from Lecointre (1965) Islands (Garda-Talavera, 1987Avila, 2000;Callapez and Ferreira Soares, 2000;Avila et al, 2002Avila et al, , 2008Garda-Talavera and Sanchez-Pinto, 2002;Meco et al, 2002;Zazo et al, 2002Zazo et al, , 2007. The palaeoecological requirements of the Sal Island fauna were recon structed by comparing our fossil data with observations of Morri and Bianchi (1995) and Morri et al (2000) on living shallow epibenthic communities.…”

“…The number and elevation of Quaternary marine terraces in Canary Islands and Sal Island are very similar (Zazo et al, 2004(Zazo et al, , 2007. In eastern Canary Islands Zazo et aL (2002Zazo et aL ( , 2003 recognized two morpho-stratigraphic units at elevations + 2 masl and + 1 masl in decreasing age order, separated by erosional features or terrestrial deposits indicative of a fall in sea level.…”

“…This paper focuses on the last and present interglacial deposits. Combined geomorphological mapping of the southern tip of the island and sedimentary facies analysis, U-series analyses, and U-Th and Radiocarbon data, most of them from Zazo et al (2007) allowed reconstructing relative changes in coastal dynamics and sea level during the high sea stands of the last � 130 Kyr. It also refers to the faunal migrations from the tropical African sea to the Mediterranean Sea during the last interglacial.…”

Tracers of Uplift and Subsidence in the Cape Verde Archipelago

“…These sediments were considered Quaternary by Silva et al (1990) but later Zazo et al (2007) suggested a broader Plio-Pleistocene age. Its presence suggests a probable contemporaneous sea-level height close to 75-80 m asl.…”