Changes in Pleistocene gastropod faunas on Fuerteventura (Canary Islands) and implications on shifting palaeoenvironmental conditions

Abstract

Malacological studies on Middle to Late Pleistocene aeolianite-palaeosurface sequences have been approached in order to detect environmental changes and system shifts on the eastern Canary Islands. Our results reveal that over the last approximately 360 ka, gastropod associations changed fundamentally, allowing the derivation of eight different biozones. The majority of these malacozones and particular species were limited to specific stratigraphic positions and periods. We therefore assume that Quaternary gastropods on Fuerteventura may offer the opportunity to correlate lithostratigraphic units on the basis of key species. Furthermore, environmental conditions could be derived from these associations pointing to colder semi-arid conditions related to the Obelus Zone around 360 to 340 ± 30 ka, a subsequent temperature rise around 340 ± 30 ka leading to moderate and dryer conditions for the Cochlicella Zone, a strong environmental change around 300 ± 30 ka with frequent ephemeral rainfalls for the Pomatias Zone and an increase in temperature and aridity for Late Pleistocene deposits linked to the Rumina Zone. We assume that shifts in malacozonation were triggered by changing climate conditions. Furthermore, the alternation between sand layers and palaeosurfaces is not continuously in conformity with malacozonation. We therefore assume these stratigraphic changes to be not primarily related to climatic forcing, but instead biased by an overlap of multiple factors. As palaeosurfaces indicate favourable conditions (increased gastropod biodiversities and distinct shrub vegetation), we assume that these were caused by increased edaphic moisture due to a better water holding capacity in silty palaeosurfaces, rather than by more humid climate conditions.