Download Abstract This study focuses on Upper Cretaceous sandstones of the

Abstract
This study focuses on Upper Cretaceous sandstones of the Eastern Pontides to identify the
source area, subaerial weathering level, and tectonic environment. Thirty four sandstone
samples from six stratigraphic sections were analyzed by Inductively Coupled Plasma-Mass
Spectrometry (ICP-MC) and by petrographic investigation. The late Cretaceous sandstones
are defined as lithic arenites and feldspathic wackes, and lithic wackes depending on
mineralogical and matrix content. The sandstones have low to moderate SiO2 contents (2559%; on average ~56 %). There are high positive correlations between SiO 2 Al2O3, and TiO2,
and negative correlations between SiO2 and K2O. Geochemically, the sandstones are classified
mainly as greywackes and lithic arenites. Chemical index of alteration (CIA) and chemical
index of weathering (CIW) values for Upper Cretaceous sandstones vary from 19 to 48% and
20 to 49% respectively. The combination of CIW/CIA values suggests little transportation
until final deposition. The ratios of Th/Sc (on average ~0.42), La/Sc (~1.81), Co/Th (~5.05)
and Zr/Hf (~39.1) of sandstone samples in the study area indicate a mafic source.
Furthermore, high light rare earth elements (LREE)/heavy rare earth elements (HREE) ratios
(on average ~19.72) and negative Eu anomalies (except in the Dagbasi section) suggest a
contribution from a felsic source. The lower trace element contents of the Upper Cretaceous
sandstones in relation to the Post-Archean Australian Shale (PAAS), which are considered to
be representative of the upper continental crust, show that the recycling processes in their
source areas were probably less intense than those of the PAAS. SiO2/Al2O3 (3.2-7.9) and
K2O/Na2O (0.3-1) ratios, together with the Th (on average ~3.3 ppm), Zr (on average ~91.9
ppm), Co (on average ~15 ppm), and Sc (on average ~12.6 ppm) contents of the late
Cretaceous sandstones of the eastern Pontides indicate a magmatic arc origin. Sandstones of
the Trabzon
region were probably deposited in fore-arc basins, and those from the
Gumushane and Giresun regions in back-arc basins.