Cretaceous Stratigraphic and Tectonic Evolution of the Eastern Margin of the Pelagonian Zone, Northern Greece

Bailey, Lydia and Picotti, Vincenzo and Schenker, Filippo and Fellin, Maria Giuditta (2017) Cretaceous Stratigraphic and Tectonic Evolution of the Eastern Margin of the Pelagonian Zone, Northern Greece. In: Abstract Volume 15 th Swiss Geoscience Meeting 15 th Swiss Geoscience Meeting, Davos, Switzerland.

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Abstract

Conventional geological mapping and stratigraphic analysis was applied to the eastern margin of the Pelagonian Zone in order to unravel the Late Creteceous detrital record of the newly discovered Kallipetra Basin. Illite crystallinity, low-temperature thermochronology, and fluid inclusion analysis helped provide new constraints on the tectonic evolution of the Vardar Zone and the eastern Pelagonian Zone, as well as deciphering how these tectonics influenced the development of the Kallipetra Basin. Following ophiolitic obduction of the Vardar oceanic lithosphere at 155-130 Ma, and exhumation of the Pelagonian Gneiss Dome at 116 Ma, the Kallipetra Basin was formed as a hybrid forearc- to foreland-type basin resting on the eroded Vardar Ophiolitic Complex (VOC) and Pelagonian basement. The basin was elongated NW-SE, parallel to the suture of the colliding Adriatic and European plates. Subaerial erosion and fluvial transport provided the first sediments, serpentinite-rich conglomerates, to the initially shallow sedimentary basin. As the basin progressively deepened, the slopes underwent frequent soft-sediment slumping, and mass flows and Pelagonian olistoliths were deposited on the bottom slopes during instability. The Pelagonian continent was positioned on the north-werstern flank of the basin, providing more quartz-rich material to the north-western slopes. The basin experienced peak depths at the Cenomanian – Turonian boundary when distinct red and green marly limestones were deposited, corresponding to OAE2 and peak global transgression. Shallowing of the Kallipetra Basin occurred in the Turonian due to sedimentation, an increasing input of serpentinite-rich material from an approaching Vardar source in the south, and global sea level fall. Rudist mounds were constructed on shallow slopes that were sloping towards the north, away from the approaching VOC. The bioherms have a core made principally of micrite and whole floating rudists (Hippurites), and the core is built on a bioclastic breccia containing rudists, sponges, echinoderm fragments, serpentinite and quartz. The mounds are asymmetric with steeper slopes on the southern flank. Flank deposits on the northern flank of the mounds consist of marls, or a series of breccias and sandstones displaying an increasing content of serpentinite. Serpentinite breccias, originating from the VOC positioned upslope, stack up against the steep southern flanks of the mound. Helvetoglobotruncana helvetica place deposition of flank deposits around ~ 93 Ma and upwards. After ~91 Ma, the VOC tectonically overrides the Kallipetra Basin. Shear heating and circulation of hot fluids created greenschist conditions at the contact, and an inverted thermal profile in the Kallipetra Basin below the tectonic contact. Apatite ages were reset. Extension occurred during the Oligocene to early Miocene, documented by a reset AFT age of 32.7 Ma, WNW-ESE trending normal faults, and NE-SW trending dextral strike slip faults.

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