UTRECHT MICROPALEONTOLOGICAL BUllETINS

The Cambrian-Ordovician sequence considered is delimited by the "Tessini
sandstone" at the base and the "Limbata limestone" at the top (see
chart I). It includes red and green fossiliferous limestones, black shales,
bituminous limestones, calcareous sandstones and conglomerates (chart I).
The total thickness of this sequence is slight, in the order of some 10 m.
Beds are thin and especially in the upper fossiliferous limestones innumerable
disconformities are present.
The occurrence of a great variety of lithological types in the basal part of
the column, and the very homogeneous lithology of the upper part of the
sequence, are the most striking features.
The gross lithological characteristics were studied in the field in 14
rock-sections (fig. 2) at a scale of 1:10. For detailed sedimentpetrographic
investigations a great number of thin-sections was studied with microscope
equipment. This investigation was concentrated on three of the rocksections,
in the south (section 1), middle (section 6) and north (section 14)
of the area respectively (fig. 2). The fossiliferous limestones were classified
according to Dunham's (1962) classification and microscopic data were
gathered concerning the disconformities, allochems, sorting, fauna and iron
compounds. The composition of the latter were established by X-ray analysis
of powder samples. Combination of the field observations and the results of
the laboratory research allowed a lithostratigraphic subdivision into four
formations and ten members of the lower two. In the correct order of
superposition these units are:
- Horns Udde Formation
- Bruddesta Formation
- Kopingsklint Formation with the informal members Kkl, Kk2, Kk3,
Kii-d1 and Kii-d2
- Djupvik Formation with the informal members Dii-d1, Dii-d2, Dii-d3, Dh 1
and Dkl'