Significance of lower Pliocene mass-flow deposits for the timing and process of collision of the Eratosthenes Seamount with the Cyprus active margin

Abstract

On the crestal area of the Eratosthenes Seamount at Site 966 an important chaotic interval composed of clast-rich, matrix-supported sediments (here named the Mass-Flow Unit) was recovered in five boreholes, situated up to 70 m apart. These sediments overlie shallow-water limestones of Miocene age and are, in turn, overlain by deep-water nannofossil ooze and sapropels of early Pliocene-Pleistocene age. Nannofossils and planktonic foraminifers indicate an early Pliocene age for the matrix, and a late Miocene to early Pliocene age for clasts within the Mass-Flow Unit. Clasts of shallow-water limestone and nannofossil chalk are both present. The matrix is mainly nannofossil ooze admixed with silt-sized reworked carbonate grains, minor quartz, and terrigenous clay. Whole-rock X-ray diffraction reveals variable quantities of calcite, dolomite, and aragonite, together with minor quartz and pyrite. Fibrous carbonate is seen in several thin sections. Limestone clasts have undergone extensive dissolution, followed by variable meteoric water cementation, presumably during Messinian emergence, Comparable Miocene-Pliocene settings onshore in Cyprus are the following: (1) formation of lower Pliocene carbonate debris flows, similar to those at Site 966, related to extensional faulting; (2) Messinian erosion, karstification, and talus formation on the flanks of a graben undergoing active crustal extension during the late Miocene; (3) formation of deep channel and related debris flows of late Pliocene age. Of these, the first and second show similarities with the Eratosthenes Mass-Flow Unit. The Florence Rise also shows some similarities.