petromagnetism

The results of petromagnetic and paleomagnetic studies of two sections of the Lower Syzran subformation (Paleocene) – Gremyachka and Klyuchi-2, located in the north of the Saratov Right Bank and represented by weakly magnetic silicites, are presented. Paleomagnetic data on sections, despite their low quality and fragmentation, are important for magnetostratigraphy, because they confirm the presence of a reverse polarity magnetozone (analogous to chron C27r and/or C26r) in the Lower Syzran subformation and its lateral stability.

The level with anomalous high values of natural remanent magnetization and Koenigsberger ratios was identify in the Upper Maastrichtian of Vol’sk depression (Saratov Volga Region). The microprobe studies of samples from this layer registered elevated concentrations of microparticles of iron, nickel, intermetallics and magnetite spherules of cosmic genesis. Similar petromagnetic anomaly was detect in the uppermost of Maastrichtian in the South Cis-Caspian (Aktolagay Plateau, Kazakhstan).

In the right-bank part of the Saratov Region, a section of terrigenous and carbonate rocks has been determined to underlie the ?sponge? horizon conventionally dated back to the Santonian. The maximum thickness of the marls, constituting a substantial portion of the section, occurs in the western part of the region.

On the base of spectral Fourier analysis of magnetic susceptibility time series of nearly 10 000 measurements of rock samples in the turonian-maastrihtian sediments, exposed near Nizhnyaya Bannovka village (Volga River Right Bank, Southern Saratov Region) there were detected long and short eccentricity cycles. Petromagnetic variations, correlated with different variants of eustatic curves detected the presence of well known sequences.

The Gubkino Horizon (Turonian-Coniacian) in the Bolshoy Kamenny ovrag section (Zhirnovsk town, Volgograd Region) has not been purposefully studied so far. As a result of biostratigraphic and magnetostratigraphic researches the carbonate rocks of the Gubkino Horizon were first divided into zones based on benthic foraminifera complexes and characterized by geomagnetic polarity and rock-magnetism data. The most part of the Bolshoy Kamenny ovrag section is covered by the reverse polarity zone.

The paper presents the results of petro- and paleomagnetic studies of two sections of Turonian – Santonian on the Samara Right Bank – near Novodevichye, Podval’e villages and detailed geological description of the Novodevichye section. The magnetostratigraphic subdivision and detailed correlation of the sections were carried out. Unknown unconformity in the Podval’e section was recognized.