Dolomitization of Biocalcarenites of Late-Tertiary Age from Northern Lanzarote (Canary Islands)

Abstract

A calcarenite interbedded in a thick pile of basaltic rocks is described from Northern Lanzarote (Canary Islands). The limestone representing a former land surface has smoothed out a former relief of volcanic cones. The rock consisted originally of probably wind-transported biocalcarenite with fragments of mainly Lithothamnium, foraminifera, serpula, bryozoans, echinoderms and a little volcanic material which increases toward the top. Dolomitization has taken place. It is strongest in the uppermost parts of the sediment and decreases downward, and is restricted to the upper 3 to 4 m below the overlying basalt; lower in the section original calcite is preserved. Further downward sedimentary material is entirely calcite. Dolomitization is probably caused by leaching of Mg out of the overlying volcanics.