Współwystępowanie zespołu miospor Corollina meyeriana, z megasporą Striatriletes ramosus sp.n. w osadach najwyższego triasu Polski

Abstract

Przedstawiono wyniki badań mega-i miosporowych osadów najwyższego triasu w rejonie Gostynia. Podano ocenę taksonomiczną megaspor, które w pracy T. Marcinkiewicz (1969) otrzymały nazwę Erlansonisporites ramosus (nomen nudum). Obecnie przeklasyfikowano je do rodzaju Striatriletes (van der Hammen 1954) Potanié 1956, nadając im nazwę gatunkową Striatriletes ramosus sp.n. Współwystępowanie megaspory Striatriletes ramosus sp.n. z zespołem miosporowym Corollina meyeriana, dokumentującym w Polsce osady wyższej części warstw jarkowskich łącznie z niższą częścią warstw zbąszynieckich, umożliwiło ustalenie pozycji stratygraficznej tego gatunku.

COOCCURRENCE OF THE COROLLINA MEYERIANA MlOSPORE ASSEMBLAGE AND MEGASPORE STRIATRILETES RAMOSUS sp.n. IN THE UPPERMOST TRIASSIC OF POLAND

Epicontinental rocks of the uppermost Triassic, occurring between the Gypsum Beds of the Keuper and Lias, are assigned to "Rhaetic" in lithostratigraphic subdivision used in Poland. So interpreted "Rhaetic" fails to correspond closely to the range of the Rhaetian chronostratigrapbic stage. "Rhaetic" strata fall within the range or Alpine Norian and Rhaetian stages but the question where to place boundary of these stages remains open.

The paper presents results of miospore and megaspore studies on rocks of the uppermost Triassic from the Gostyń region, Fore-Sudetic Monocline. Stratigraphic position of these rocks was defined on the basis of relatively complete palynostratigraphic scheme established for western Poland. An assemblage corresponding to the Corollina meyeriana assemblage, more precisely its subassemblage "b" in the above palynological scheme, has been found in the boreholes 5 G, 27 G, 40 G, 41 G, and 46 G. The assemblage comprises its nominal species and the taxa Corollina zwolinskai Lund, Classopollis classoides (Pflug) Pocock et Jansonius, Granuloperculatipollis rudis Venkatachala et Goczan, Enzonalasporites vigens Leschik, and others (Table 1), being characteristic of upper part of the Jarków Beds and lower part of the Zbąszynek Beds. It appears similar to microflora of the Steinmergelkeuper cf the G.D.R. (E. Schulz, 1967) and the Corollina Enzonalasporites zone differentiated in both the Postera Schichten of the F.R.G. and Lower "Rhaetic" of Denmark by J. Lund (1977). K.R. Pedersen and J. Lund dated that zone at the Norian.

In the borehole column 39 G there was differentiated the Ricciisporites tuberculatus assemblage with the species Rhaetipollites germanicus Schulz, Limbosporites Iundbladii Nilsson, Cyathidites australis Couper, and others (Table 1). It characterizes microflora of lower part of the Wielichowo Beds, which displays some features in common with those of the Middle and Upper "Rhaetic" of the G.D.R. (E. Schulz, 1967), the Rhaetipollis Limbosporifes (Middle "Rhaetic") and Ricciisporites Polypodiisporites (Upper "Rhaetic") of the F.R.G. and Denmark (J. Lund. 1977). Despite of differences in views on ranges of the Norian and Rhaetian stages it may be assumed that age of this microflora corresponds to the Rhaetian in the standard subdivision.

At depths 233.0-247.0 m in the borehole column 46 G there was found megaspore assemblage comprising Trileites pinguis (Harris) Potonie, Bacutriletes tylotus (Harris) Potonie and other taxa. In the literature (T.M. Harris, 1935; W. Jung, 1960; H.J. Will, 1969; F. Bertelsen, O. Michelsen. 1970; T. Marcinkiewicz, 1971) the taxa were usually reported from the Upper "Rhaetic" or, sometimes, lower parts of "Rhaetic". The recorded assemblage also comprised some new species: Talchirela granifera sp. n., Striatriletes ramosus sp.n., and others.

Taking into account dating of the studied borehole interval on the basis of miospores it is assumed that stratigraphic range of the above mentioned megaspore assemblage comprises strata of upper parts of the Jarków Beds and lower part of the Zbąszynek Beds.

Description of the megaspores

Talchirella granifera sp.n.

(Table IV, Fig. 3)

Holotypus: Table IV, Fig. 3.

L o c u s  t y p i c u s: Gostyń area, borehole 46 G, depth 246.0-247.0 m.

S t rat u m  t y p i cum: Jarków - Zbąszynek Beds („Rhaetic").

De r i vat io  n o m i n is: From Lat. granifera - grain-bearing.

M ate r i a I: Eight specimens.

D e s c r i p t I o n. Megaspores subcircular in outline and 340 -600 μm in diameter. Triradiate rays in the form of low ridges, attaining 0.8 of length of spore radius. Arcuate ridges missing. Whole surface of spores uniformly covered with fine verrucae. Verrucae locally merging with one another to form elongate and flat elements of ornamentation, being also marked on ridges of the tetrad mark. Spore surface somewhat shining, yellow-brownish in colour.

R e m a r k s. The species T. granifera sp.n. appears very similar to Pusulosporites permotriassicus Fugl. in style of ornamentation of exine (closely spaced verrucae). However, comparison of representatives of the former and those of P. permotriassicus figured by R. Fuglewicz (1977, table 29 and Figs. 1, 2) shows marked differences in ornamentation of spore surface and development of tetrad mark. T. granifera sp.n. also resembles Talchirella daciae Antonescu et Taugourdeau Lantz from the Middle Buntsandstein of Poland. G.D.R., and Romania (E. Antonescu, J. Taugourdeau Lantz. 1973). differing markedly in character of elements of ornamentation.

O c cur r e n c e. Fore-Sudetic Monocline: upper part of the Jarków Beds and lower part of the Zbąszynek Beds.

Striatriletes ramosus sp.n.

(Table Ill, Figs. 1-4)

Ho lot y p u s: Table Ill. Fig. 1a, b.

L o c u s t y p i c u s: Praszka -Gorzów Sląski area, borehole Praszka 3/lII, dc;pth 154.95 m.

S t rat u m t y p i cum: Gorzów Beds ("Rhaetic").

De r i v a t io  n o m i n i s: After Lat. ramosus -branching.

M ate r i a I: Fifteen specimens.

D e s c r i p t ion. Megaspore subcircular-triangular in outline, 300 -500 μm in diameter. Triradiate rays with ridges with wavy margin and 40-60 μm (or sometimes up to 100 μm) in height. Contact areas generally indistinguishable. Arcuate ridges missing. Whole surface of spores ornamented with winding ridges with rounded crest line, 25-40 μm high and 20-25 μm thick; ridges tending to form reticle with large, elongate meshes in distal part to run more or less radially towards apex at proximal surface, where they disappear. In the latter area small projections appear on some specimen. Spore surface shining, brownish in colour.

R e m a r k s. The new species resembles Cretaceous Striatriletes radialis (Gunther, Hills) Sweet (P.R. Gunther, L.V. Hills, 1972; A.R. Sweet, 1979), differing in somewhat larger size and more massive ridges at surface.

There was found a single tetrade of spores Striatriletes ramosus sp.n.

O c c u r r e n c e. Fore-Sudetic Monocline: upper part of the Jarków Beds, Zbąszynek Beds.