科研之友
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摘要
The paper presents a comparative analysis of a Lower Kimmeridgian layer with bored and en crusted hiatus concretions collected in three study areas, located in Central Poland. These studies demonstrate distinct similarities be tween the hiatus concretions in terms of their origin, development and strati graphic position. The layer with its character is tic concretions seems to rep re sent an important marker horizon for the Lower Kimmeridgian successions in Central Poland. The identification of this marker horizon in drill cores and exposures could be important for definition of the strati graphic position of the sediments, which other wise lack appropriate biostratigraphic in formation. The matrix of the concretions is composed of pelagic calciturbidites, which reflect flooding of the early Kimmeridgian plat form. These sediments were lithified early and formed a hardground. The origin of the hiatus concretions probably is related to erosion of the hardground, followed by redeposition and several phases of exhumation and erosion, preceding final burial. The characteristic ecological successions, observed in the concretions, document an evolution from soft to firm and hard marine sub strates, typical of hardgrounds and evidenced by various bur rows, borings (Gastrochaenolites, Trypanites), and epizoans. Calciturbidite sedimentation, hardground erosion and redeposition of the hiatus concretions, known from deposits of the Platynota Zone in Central Poland, were associated with synsedimentary activity of the Holy Cross Fault, on the NE margin of the extensive, tectonic Malopolska Block.
- 出版日期2014
