Mid and Late Holocene sea level variations in the Canary Islands
Abstract The eastern coast of Fuerteventura (Canary Islands, Spain) hosts the most complete and representative emergent Holocene marine deposits in the middle latitudes (27°N to 30°N) of the eastern Atlantic Ocean. The deposits consist of berms of gravel and foreshore sands which form beach rocks comprising >62 bed sets, with each bed set containing dozens of individual laminations suggesting a cyclical cause as, for example, the orbital movement of the Earth. Calibrated radiocarbon ages place a group of older Holocene highstands of Fuerteventura at around the Mid-Late Holocene boundary (around 4.2 kyr B.P.), and another group of more recent highstands in the Dark Age Period (around 1.4 kyr B.P.) of the Northern Hemisphere. They have been recorded at 4 m and 3.5 m apmsl respectively. The present-day tidal amplitude is around 3 m. Assuming a similar value for the Holocene, the corresponding relative sea level rises were around 2.5 m and 2 m apmsl respectively. Moreover, terrestrial deposits intercalated between the marine deposits indicate a lowering of the sea level at ca. 3 kyr B.P. When the sea levels reached their highstands during these two periods, the sea surface temperatures (SST) at the southern tip of the cold Canary Current were, respectively, 0.5 and 1.5 °C colder than the present-day SST (21.23 °C). The fossil fauna content confirms that these highstands occurred in cold conditions. In contrast, the present SST reaches the range of temperatures of the Holocene Optimum in the area. Fuerteventura has been vertically stable since the last interglacial period, and the sedimentology of the deposits precludes an origin from tsunamis or storms. This island is in a far-field region in terms of glacial isostatic adjustment (GIA) processes. Here, we suggest that the deposits may be related to GIA and ice mass losses effects in the Southern Hemisphere.