Clay mineral stratigraphy of Miocene to recent marine sediments in the central Mediterranean

• Main Author: Visser, J.P. de
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 1992
• Subjects: Aardwetenschappen; clay minerals; marine sediments; Mediterranean Region; North Atlantic
• Online Access: https://dspace.library.uu.nl/handle/1874/238501

X-ray diffraction analyses were made of the smaller than 2 J.Lm fraction from about 1250 samples of the central Mediterranean Miocene to Recent and the southeastern North-Atlantic Miocene in order to reconstruct climatic changes. Relative quantities of the clay minerals chlorite, illite, pyrophyllite, smectite, kaolinite and palygorskite and the accessory minerals quartz and goethite were obtained with a new quantification method, combining peak-area and peakheight measurements on the diffractograms. Random mixed-layers and sepiolite were found but not quantified separately. Detailed calcareous nannofossil and planktonic foraminiferal biostratigraphic data - and for the Late Miocene to Pleistocene also geomagnetic data - allowed time-stratigraphic correlation of thirteen clay mineral intervals and twenty six subintervals distinguished in the most detailed records. The mineral curves as well as a principal component analysis of the averages per (sub)interval show the existence of regional differences in clay composition within the central Mediterranean area and between the two study areas. These differences were preserved in the course of time and are related to source characteristics and sorting during transport. Smectite dominates the associations. In most intervals the vertical record of strong smectite trends and fluctuations is not a reflection of contemporaneous changes in soil formation induced by climate. Lateral comparison between curves for Pliocene sections in Sicily, Calabria and the Tyrrhenian suggests that the main mechanism is to be looked for in changes in erosion and reworking from older sedimentary sequences, possibly of Messinian Age. Changes were caused by variation in precipitation and in relief formation. A more distant supply of clay particles as aeolian dust derived from Paleogene sediment outcrops in North Africa is reconstructed for the Late Miocene to Pliocene of the entire central Mediterranean. This signal is suppressed by local riverine supply at times of tectonic uplift causing ...