Tentakulity i ich znaczenie dla stratygrafii (dolny dewon)

Abstract

TENTACULITES AND THEIR STRATIGRAPHIC IMPORTANCE (LOWER DEVONIAN)

Summary

Lower Devonian tentaculites have been previously described from boreholes Ciepielów IG-l, Krowie Bagno IG-1, and Zakrzew IG-3 (B. Hajłasz, 1974), situated in the Radom-Lublin area (Fig. 1). The presently described tentaculites originate from boreholes Białopole IG-l and Izdebno IG-1, which are also situated in the same area.

Two characteristic assemblages of tentaculites occur in boreholes Izdebno IG-l and Białopole IG-1: assemblage  I – Gedinian and assemble II – Siegenian (Fig. 2).

Deposits situated in borehole Izdebno IG-l at a depth of 4000.8 –3855.0 m. and in borehole Białopole IG-l at a depth of 1523.0 –1549.10 m. can be described as Gedinian, since they contain tentaculite assemblage I, known from boreholes Ciepielów IG-1 and Krowie Bagno IG-1. This assemblage is also similar to tentaculite's which occur in the Borszczów Beds and the Czortków Beds in Podolia.

The Borszczów Beds and the Czortków Beds have been correlated with Gedinian deposits inPoland(B. Hajłasz, 1974).

Deposits which occur in borehole Izdebno IG-1 at a dp.pth of 3855.0 –3,767.8 m. and in borehole Białopole IG-1 at a depth of 1412.0 –1333.9 m. can be described as Siegenian, since tentaculite assemblage II identified here is similar to that in boreholes Ciepielów IG-1, Krowie Bagno IG-1 and Zakrzew IG-3.

Tentaculite assemblage II is also similar to tentacurites which occur in the Iwaniewo Beds in Podolia, previously correlated with Siegenian deposits inPoland(B. Hajłasz, 1974).

Palaeontological descriptions

Tentaculites urbaneki sp. novo

(PI. I, Figs. 1–4)

Shell in the shape of a narrow cone. Proximal part of shell characterized by sculpture which consists of very tiny rings, closely adhering to one another. Since these rings are narrow and tiny, they are similar in habitat to striae. Distal part characterized by more diversified sculpture. The rings are distinctly outlined here.

Narrowing between rings are filled with striae.

Tentacutites urbanek sp. novo was found in borehole Izdebno IG-l, in the Radom-Lubin area, in Gedinian deposits.

Turmalites crassaformis sp. nov.

(PI. III, Fig. 12; PI. V, Figs. 22–24)

Shell of moderate dimensions, conical. Ornamentation of proximal part of shell in the form of rings, irregularly placed on the surface of shell. Distal part with characteristic gaps – narrowing – between rings, filled with well-developed striae.

Turmalites crassaformis sp. novo occurs in borehole· Izdebno IG-I, in Gedinian and Siegenian deposits.

Prolatonius izdebnensis sp. nov.

(PI. VII, Figs. 32–35)

Shell small, conical. Ornamentation of proximal part of shell in the form of rings, very fine, closely adhering to one another. Distal part differs above all in width of shell, which becomes much larger at the boundary between proximal and distal parts. In proximal part the rings are narrow, densely packed.

Prolatonius izdebnensis sp. nov. was found in borehole Izdebno IG-1, in Gedinian and Siegenian deposits.

Dicricoconus crocotillus sp. novo

(Pl. XII, Figs. 64, 66, 67)

Shell small, greatly elongated in outline. Part of shell directly adjacent to embryonic chamber is characterized by ornamentation in the form of very fine, closely packed rings. In the remaining part of shell – till the very aperture – there are two types of rings, of larger and smaller diameter. Smaller rings of the second type appear in narrowings between larger rings of the first type. Both types of rings have a common feature: they are narrow. Number of rings of the second type varies from one to seven. Differentiation in the rings of the second type is an essential feature of this species. These rings differ both in shapes and in dimensions.

Dicricoconus crocotillus sp. nov. occurs in borehole Izdebno IG-1, in Siegenian deposits.

Parvulites sp. A

(PI. VII, Fig. 40)

Shell small, conical. Length of shell about8 mm. Ornamentation of proximal part of shell in the form of ring-like striae, very closely packed. Very well-developed rings appear in distal part. Well-developed striae occur between rings.

Parvulites sp. A occurs in borehole Izdebno IG-1.

Parvulites sp. B

(PI. VII, Figs. 36, 39)

Shell small, conical. Length of shell up to7 mm. Whole surface of shel1 covered with very tiny ring-like striae. Rings begin to appear close to the aperture.

Parvulites sp. B occurs in borehole Izdebno IG-4.

Odessites sp. A

(PI. XI, Fig. 60)

Shell large, orthoconical. Whole surface of shell covered with large, and thick rings, their diameters becoming much larger in distal part, near the aperture. Three rings of relatively small diameters occur at the very aperture.

Odessites sp. A was found in borehole Izdebno IG-1 in Siegenian deposits.

Multiconus sp. C

(PI. IV, Fig. 17)

Shell, characterized by complex structure, composed as if of two cones. Size of shell up to7 mm. Ornamentation of proximal part of shell in the form of wide, rounded rings of relatively large diameters. Central part (junction of proximal and distart parts), covered with very tiny and well-developed rings. Distal part covered with rings similar to those in proximal part.

Multiconus sp. C occurs in borehole Izdebno IG-1, in Siegenian deposits.