Akademik Veri Yönetim Sistemi
GEOLOGICA CARPATHICA, cilt.54, sa.6, ss.377-384, 2003 (SCI-Expanded)
This study deals with the volcanic blocks occurring within the Upper Coniacian-Santonian red limestone which crops out in the Macka area (Trabzon, NE Turkey). The red limestones are thin to medium-bedded, and mostly consist of wackestones, rich in planktonic foraminifers with subordinate radiolarians and inoceramid bivalve fragments. In the upper part of the formation, volcanic blocks occur which consist of andesite to dacite and show microlitic-porphyritic texture with plagioclase and pyroxene as pbenocrysts. Chemical data indicate that these volcanic rocks are calc-alkaline in character and show similar trace and rare earth element chemical signatures with those of arc related volcanics. The limestones and the volcanic blocks are discoloured in proximity of the boundary. The contact relationships suggest that the volcanic lava blocks were still hot when they fell on the unlithified pelagic limestone muds. These data emphasize that the earliest Cretaceous volcanism started at the Late Coniacian-Santonian boundary in the Eastern Pontide volcanic arc.