Pages: 251 - 260
Abstract: Two multiple stratified volcano-sedimentary Paleogene sections built of breccia-conglomerates and sandstones (incl. epiclastic), marls, limestones (incl. reef and bioclastic) and zeolitized pyroclastic rocks (interpreted as pyroclastic flow deposits mainly) were studied and correlated. The deposits are divided into superposed and interfingered informal lithostratigraphic units. The natural remanent magnetization of the zeolitized pyroclastics was determined as thermal remanent magnetization (TRM) or partial TRM, and that of the sediments — as detrital remanent magnetization and post-detrital remanent magnetization. The characteristic remanent directions allowed straightforward construction of magnetostratigraphic profiles and yielded 12 reliable magnetic polarity zones and sequences of zones in the sections studied. The correlation of the sections was based on the magnetic polarity zones position, lithological features of the rocks and three 40Ar/39Ar age determinations of the zeolitized pyroclastics from different levels of the sections. The consistent (Rupelian — 32.28±0.07 to 31.82±0.07) ages plot entirely into the 12r polarity chron on the Geomagnetic Polarity Time Scale (GPTS) (Cande & Kent 1995). The data presented show that the polystage formation of the pyroclastic flows and the change of the contemporaneous sedimentation from clastic to biogenic took place in a relatively short time span of about 0.46 Ma.
Keywords: Paleogene, Bulgaria, Eastern Rhodopes, correlation, lithology, magnetostratigraphy, 40Ar/39Ar ageDownload PDF document Show Text Version