Characterisation of two fluvio-lacustrine loessoid deposits on the island of Gran Canaria, Canary Islands

Abstract

The Canary Islands are close to the largest desert in the world, the Sahara, and as a result, the influence of air-transported dust in the area is of great significance. The present analysis consists of a study of two deposits in the NE and NW, respectively, of the island of Gran Canaria, considered as fluvio-lacustrine loessoids. They exhibit the characteristics of aeolian deposits, re-worked by fluvial processes, at the mouth of gullies, and later edaphized. In the NW profile (Gáldar), formed from 400 ka to present, there are four different levels with abundant manganese stains over each and separated by dense calcrete laminations. This sequence may be associated with cyclical processes of deposits in humid conditions, and drying (Mn mobility), plus the formation of arid soil (carbonate precipitation). The formation of the Galdar profile took place between the Upper Pliocene and the Upper Pleistocene–Holocene. The NE profile (Jinámar) reveals a similar cyclic profile. The Jinámar fluvio-loess deposit was formed between the Upper Pliocene and the Upper Pleistocene (1.96–0.1 Ma). The high percentage of the silt fraction (60–90%) and the high percentage of quartz, a mineral which is totally imported from the Sahara Desert, are the main arguments in favour of the definition of these loess-like deposits.