The geological history of the Earth is an indomitable aspiration of its lithosphere structures (undoubtedly, as well as the rest geospheres, which are inaccessible to observation) for differentiation and ordering, i.e. for self-organization. However till now, geology and geological analysis show that in the course of evolution systems aspire to equilibrium states and supposedly accumulate deformations. The deformations, as links of the supposed evolution, become the principal object of investigations. A result of such an ideal study is a reconstruction of dynamic conditions, under which systems began a calculation of accumulated deformations, successively approaching the observed pattern. In other words, it is necessary to reconstruct the initial point of the dynamic trajectory according to the final result. At present the overwhelming majority of geologists are convinced that if we cannot deduce the properties of the object under study from the properties of its elements, the reason for this is our poor knowledge of these elements properties or peculiarities of their pairwise interactions. <...>

Die Studie der Art Exogyra sigmoidea REUSS, 1844 aus der Brandungsfazien der böhmischen Kreide ist ein Teil der vorbereiteten Monogralie über die Familie Ostreidae. Ausser den einführenden Kapiteln und dem biostratigrafischen Teil mit Beschreibung der Lokalitäten, wurde die Aufmerksamkeit hauptsächlich der Morfologie, Ontogenesis, Variabilität, Ökologie, den Mikrostrukturen und dem Bau der Gehäuse der studierten Art gewidmet. Da der Holotypus nicht festgestellt wurde, wurde aus dem Topotyp-Material der Neotypus ausgesucht und abgebildet und diagnostische Merkmale angeführt, durch welche sich die Art Exogyra sigmoidea REUSS von einigen verwandten Arten unterscheidet [Exogyra reticulata REUSS, 1846 und Exogyra haliotoidea

In 1989, the chief geologist of BP Exploration and his senior colleagues recognized the need to expand the company’s resource of sequence stratigraphers, and created the Stratigraphic Studies Group. This group initially included a few experts, but was composed chiefly of a mixture of willing geophysicists, sedimcntologists and bio-stratigraphers, who were to train as sequence stratigraphers, but more importantly, were to bring the expertise from their own disciplines to bear on sequence stratigraphy. This merging of geological disciplines with sequence stratigraphic principles first saw the light of day as BP’s ‘Introduction to Sequence Stratigraphy’ course. This course has been given internally since 1991, and has been presented in whole or in part to over a dozen national oil companies and at several international geological and geophysical conferences.

Significant problems are being encountered by stratigraphers as they attempt to apply Exxonian sequence analysis to the depositional record. The most serious problem is one of consistent and objective boundary recognition. The unconformable portion of the boundary usually can be recognized with reasonable objectivity but a major problem occurs when the boundary is a "correlative conformity". The Exxon model defines such a surface as the depositional surface which existed at the time of the end of base level (relative sea level) fall. In many cases this theoretical surface has no apparent lithologic expression and cannot be recognized objectively. Thus correlation of a depositional sequence throughout a basin is either impossible or is an extremely subjective exercise.