Portal de Periódicos da CAPES

CONFACIES DIFFERENTIATION AND UPPER MIDDLE ORDOVICIAN CORRELATION IN THE BALTOSCANDIAN BASIN

1995; Estonian Academy Publishers; Volume: 44; Issue: 2 Linguagem: Inglês

10.3176/geol.1995.2.01

1736-7913

Valdar Jaanusson,

Geological Formations and Processes Exploration

It is suggested that the Ordovician belt with the distinctive North Estonian lithology and benthic fauna the North Estonian Confacies Belt does not extend as far to the west as previously believed.The considerable thickness of the post-Tremadocian Lower Ordovician sequence in the submarine South Bothnian district,revealed by borings, is comparable to that in the Jelgava depression of western Latvia, indicating that the Ordovician depositional history of the Baltoscandian basin is.more complicated than has been assumed.The new term Haljala Stage is introduced for the portion of the upper Middle Ordovician sequence in the Baltoscandian basin that com- prises the previous North Estonian Idavere and Johvi stages; the rank of the two latter units is reduced to substages.It is emphasized that the boundaries of biozones based on planktic organisms, such а$ conodonts, graptoloids and chitinozoans, seldom coincide with the levels at which benthic faunas change.A new species, Amplexograptus balto- scandicus n. sp., is described.