Volume 18 (2012): Issue 1 (March 2012)

The 1st Middle-Polish (1st Lusatian) Lignite Seam is exploited in open-cast mines in central Poland. A large number of lignite lithotypes, grouped in four lithotype associations, are distinguished: xylitic, detritic, xylo-detritic and detro-xylitic lithotype associations, which show various structures. Each lithotype association was produced under specific peat-forming environmental conditions. In the case of the lignite seams under study they represent all the main environments that are known from Neogene mires, i.e.: fen or open water, bush moor, wet forest swamp and dry forest swamp.

For a simple and practical description in the field of both the lignite sections and borehole cores, a new codification for lignite lithotypes is proposed. It is based on the codification of clastic deposits (lithofacies). The practical value of the new lignite lithotype codification is examined in three vertical sections of the 1st Middle-Polish Lignite Seam.

The Kashkan Formation (?Palaeocene to Middle Eocene) in the Zagros fold-thrust belt, SW Iran, which is intercalated between to marine limestone formations, consists of conglomerates, sandstones and siltstones. The sedimentology and the palaeogeography of the Kashkan Formation had not received any attention thus far, but have now been studied in seven sections, situated in the province of Lorestan. The sediments form twelve lithofacies, three ichnosubfacies and seven architectural elements, which are described, depicted and analysed. The analysis leads to the conclusion that most sediments accumulated in a low-sinuosity, low-gradient braided-river system (characterised by mainly unidirectional palaeocurrent directions, and by sheetfloods), that occasionally showed meandering characteristics (represented by overbank deposits and large bars). The deposits of this system closely resemble those of the South Saskatchewan River in Canada, which is considered as the classical example of a sand-bed braided river. The river flowed roughly from North to South, as deduced by palaeocurrent indicators such as imbrication and large-to medium-scale trough cross-stratification (direction measured in the trough axes). This current direction is supported by the southward to south-westward thinning of the formation and by the diminishing average grain size in the same direction. The trace fossils in the Kashban Formation fit all in the Skoyenia ichnofacies, which has here three ichnosubfacies which allow a more detailed palaeoenvironmental reconstruction, indicating that the braided stream passed into the low-energy shoreface zone of a tidally-influenced sea.

Angiosperms evolved rapidly in the late Mesozoic. Data from the genetic-based approach called ‘molecular clock’ permit an evaluation of the radiation of flowering plants through geological time and of the possible influences of Mesozoic mass extinctions. A total of 261 divergence ages of angiosperm families are considered. The radiation of flowering plants peaked in the Albian, early Campanian, and Maastrichtian. From the three late Mesozoic mass extinctions (Jurassic/Cretaceous, Cenomanian/Turonian, and Cretaceous/Palaeogene), only the Cretaceous/Palaeogene event coincided with a significant, abrupt, and long-term decline in angiosperm radiation. If their link will be further proven, this means that global-scale environmental perturbation precluded from many innovations in the development of plants. This decline was, however, not unprecedented in the history of the angiosperms. The implication of data from the molecular clock for evolutionary reconstructions is limited, primarily because this approach deals with only extant lineages.

An exceptional concentration of almost identical depressions exist near the small towns of Krotoszyn, Koźmin and Raszków (southern Wielkopolska). Their origin is, however, different from that of the typical post glacial-relief: they are Man-made enlarged thermal-contraction structures that developed at the very end of the Middle Polish (Warthian) glaciation and during the North Polish (Weichselian) glaciation, most probably under periglacial conditions.