Pionowe struktury bioturbacyjne w osadach kambru północnej Polski

Abstract

Na podstawie badań struktur bioturbacyjnych, stanowiących przedmiot pracy, wyprowadzono wnioski dotyczące środowiska sedymentacji osadów kambru oraz kierunku dolnokambryjskiej transgresji morza w północnej Polsce.VERTICAL BIOTURBATION STRUCTURES FROM CAMBRIAN DEPOSITS OF NORTHERN POLANDThe structures identified include U-shaped Arenicolites burrows and simple vertical burrows of Monocraterion and Tigillites. Tigillites burrows differ from Monocraterion burrows in the lack of concentric structure in horizontal section, i.e. the lack of sandy spine, inside pipes, and from Skolithos burrows - in the development of funnel-shaped outlets.Vertical-horizontal burrows cf. Teichichnus are the most common here. They differ from typical burrows of that ichnogenus in depth (vertical dimension) exceeding their length (longer horizontal dimension). In thin sandstone layers there are found burrows similar to teichichnia (series of subhorizontal pipes set one above another) preserved in the form of muddy endichnia.The presence of Monocraterion, and Tigillites burrows and the lack of Skolithos burrows known from the southern Scandinavia indicate that the rate of sedimentation was somewhat greater in the northern Poland than in the latter region (cf. A. Hallam, K. Swett, 1966).A map of frequency of vertical bioturbation structures was drawn for the Lower .Cambrian (Fig. 1). The map shows that the zone of shallow-water, partly littoral sedimentation possibly influenced by tides was stretching N and NE of line running from SW through location points of boreholes Żarnowiec, Darżlubie, Hel and Bartoszyce and further to NE. The distribution of isolines on the map. Indicates that Early Cambrian marine transgression was spreading in S-N and SW-NE directions in the Northern Poland.