Peculiarities in the behavior of the entropy diameter for molecular liquids as the reflection of molecular rotations and the excluded volume effects

The behavior of the diameter of the coexistence curve in terms of the entropy and the corresponding diameter are investigated. It is shown that the diameter of the coexistence curve in term of the entropy is sensitive to the change in the character of the rotational motion of the molecule in liquid phase which is governed by the short range correlations. The model of the compressible effective volume is proposed to describe the phase coexistence both in terms of the density and the entropy.Comment: 22 pages, 8 figures, 3 Table

Sedimentary cycles in a Mesoproterozoic aeolian erg-margin succession: Mangabeira Formation, Espinhaço Supergroup, Brazil

Aeolian systems were abundant and widespread in the early Proterozoic, post-2.2 Ga. However, the majority of aeolian successions of such great age are intensely deformed and are preserved only in a fragmentary state meaning that, hitherto, few attempts have been made to apply a sequence stratigraphic approach to determine mechanisms of aeolian construction, accumulation and preservation in such systems. The Mangabeira Formation is a well preserved Mesoproterozoic erg successions covering part of the São Francisco Craton, northeastern Brazil. The lower unit of the Mangabeira Formation (~ 500 m thick) comprises aeolian deposits of dune, interdune, and sand-sheet origin, as well as some of waterlain origin. These deposits are organized into vertically stacked depositional cycles, each 6 to 20 m thick, and characterized by aeolian sandsheet and waterlain deposits succeeded by aeolian dune and interdune deposits indicative of a drying-upward trend. Aeolian cross-strata exhibit a mean dip direction to the north. Each of these cycles likely arose in response to climatic oscillation from relatively humid to arid conditions, possibly related to orbital forcing. The lower unit of the Mangabeira Formation comprises up to 14 erg sequences. The accumulation and preservation of each was determined by the relative rate of water-table rise and the availability of sand for aeolian transport, both of which changed through time, resulting in the preservation of a succession of repeated drying-upward cycles