O występowaniu w Polsce rhizosolenii - problematycznych metakonkrecji

Ewa Odrzywolska-Bieńkowa, Hanna Senkowiczowa



Calcareous tubes were found in Miocene deposits penetrated by borehole Twardawa IG-1 (Opole, Silesia) at the depths of 562.6 m and 545.6 m and in Lower Muschelkalk deposits at Wolica (southern margin of the Holy Cross Mts). The tubes are about 1 mm long and 0.25 mm wide. Their outer surface is nonuniformly rough and the inner is smooth. They are irregular in shape, sometimes incurved or branching. All the tubes are empty. Analogous tubes were described by H.Hiltermann (4) who described them as rhisosolenias and accepted the point of view of A. Kumm (7) that they are metaconcretions presumably originating around fine plant rootIets. They are connected neither with any rock type nor formation but they appear to be a good index of off-shore facies of stagnant waters. In borehole Twardawa IG-1 the rhisosolenia assemblage occurs in brackish deposits of the Kłodnice beds (M3), passing downwards into limnic deposits with brown coal. They were found together with shells of small gastropods and pelecypods. It seems that they were formed in the course of sedimentation of the Kłodnice beds, which is suggested by both their position in the profile, beneath clearly marine Lower Badenian deposits, and the depth of occurrence and sedimentary environment of deposits yielding them. Up to the present the rhisosolenias were not found in Miocene deposits from other parts of Poland. In Europe they are known from 7 localities of Tertiary deposits only (F. R. G. and Portugal). All these records are, however, connected with subsurficial deposits so the rhisosolenias may be related to a younger, post-Tertiary floras. At Wolica, rhisosolenias were found in sample collected at the depth of about 1 m from quarry surface. They were found together with Triassic foraminifers, siliceous sponge spicules, ostracods, pelecypods, echinoderms, conodonts and fish remains. They are accompanied by numerous, still unidentified plant remains which shape and mode of preservation suggests, according to Professor J. Bobrowska, their post-Triassic and possibly Quaternary age. Therefore, despite of the cooccurrence of rhisosolenias with marine Triassic fauna their presence seems to be connected with Quaternary flora. The occurrence of rhisosoIenias are known to occur in aluvial and diluvial deposits from 8 localities from the Hannover area. They are also known from older deposits from 4 other localities but there they are always limited to subsurficial zone. Therefore they may be younger than deposits in which they were found.

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