Numulity z Poręby k. Myślenic (polskie Karpaty Zachodnie)

Abstract

Przedstawiono wyniki badań eoceńskich dużych otwornic pochodzących z osadów fliszowych jednostki podśląskiej. Opisano Nummuliles britannicus, nie znany dotychczas z Karpat polskich. oraz nowy gatunek - Nummuliles burtani sp. n. Na bazie materiału z Poręby rozpatrzono możliwość gatunkowego oznaczania numulitów w szlifach mikroskopowych.NUMMULITES FROM PORĘBA NEAR MYŚLENICE (POLISH WESTERN CARPATHIANS) Paleogene larger foraminifers have been found to occur in masses in black silty gravelstone, an equivalent of the menillite shales, in the section of the Subsilesian unit al Poręba near Myślenice (for detailes description of that section see J. Burtan, 1985). The Poręba locality is the richest of larger foraminifer localities known in the Polish Flysch Carpathians (Table 1). The material from the Poręba locality comprises numerous specimens assigned to a new species, Nummulites burtani sp. n., and a species Nummulites britannicus Hantken, up to the present unknow from the Carpathians. Order Foraminiferida Eichwald, 1830 Suborder Rotallina Delage et Herouard. 1896 Family Nummulitiidae de Blainville. 1825 Genus Nummulites Lamarck, 1801 Nummulites burtani sp. n. (Table 1, Figs. 1 - 5) H o l o t y p u s: Form A, specimen no. POR 31 - Table 1, Figs. 3,4. Geological Institute, Cracow. P a r a t y p e s: Form A, specimen no. POR 30 - Table 1, Figs. 1-2; specimen no. POR 32 - Table 1, Fig. 5. Geological Institute, Cracow. S t r a t u m  t y p i cum: Passage beds between the Hieroglyhp and Menillite Beds of the Subsilesian unit, Upper Eocene. L o c u s  t y p i c u s: Poręba village near Myślenice, 30 km south of Cracow. D e r i v a t I o  n o m i n is: burlani - in honour of an outstanding Carpathian geologist, Jadwiga Burtan.D i m e n s i o n s1: D/E 3.2/0.8, 4.4/ 0.9, 5.7/1.1T/R 2/1.4, 3/2.7growth of whorl 1 - (1 - 1.4) - (1.8 - 2.5) number of chambers in a quater of whorl ¼, 2/6 – 7, 3/7 – 9h/l 1 1.6 - 2.5 a = 0.30 - 0.37 mm, b = 0.43 mm, c = 0.59-0.61 mm D i a g n o s i s. Test flat, with rounded margins. Test surface with clearly marked elongations of sutures, arcuate in outline and with course disturbed in central part of the test. Whorls quickly growing in height; sutures arcuate, crescent in upper part; chambers high, nucleoconch of the isolepidine type. R e m a r k s. Nummulites burtani sp. n. resembles Upper Eocene species N. puchellus de la Harpe, differing in the ratio D/E and dimensions of embryonic apparatus. For N. pulchellus from the Tatra Mts. D/E = 3 - /1.25 – 3, a = 0.2 - 0.25 mm, and b = 0.35 - 0.44 mm, and from the USSR - a = 0.15 - 0.2 mm, and b = 0.25 - 0.3 mm. The new species is presumably of the Upper Priabonian age. Such age is assumed as the species seem to represent a derivative of the species N. pulchellus and the "assemblage" does not comprise any forms which would be younger than Upper Priabonian. O c c u r r e n c e. Carpathians, Poręba near Myślenice - Subsilesian unit, Upper Eocene. Numerous and exceptionally well preserved nummulites found in the silty gravelstone from the above mentioned rocks of the Subsilesian unit from the Poręba locality near Myślenice form a collection highly valuable for detailed paleontologicai studies on this group as material found elsewhere in the Carpathian flysch is usually unsatisfactorily preserved and poor in species. Results of studies on seven nummulite species - Nummuliles striatus, N. incrassatus. N. atacicus, N. partschi tauricus, N. laevigatus. N. britannicus, N. burtani sp. n. - are given below. The species have been selected for the analysis on account of their high frequency in the material. After making specific identifications, the specimens were cemented with glue and cut to obtain variously oriented thin sections. Results of analysis of the material shown in the Tables appear still insufficient for obtaining complete characteristics of the selected species on the basis of thin section. A comprehensive, detailed analysis of the method of specific identification of nummulites from the Polish Carpathians in thin sections and the polished ones (i. e. in similar images), should be possible when rich comparative material, that is material comprising all the possible sections of specimens of a given species, becomes available and the whole specific composition of the fauna is known. However, such material is still not available. The hitherto obtained results of studies on nummulites in thin sections make it possible to draw the following conclusions. Sections revealing features important for identifications include equatorial and axial ones as well as oblique sections when they pass close to protoconch. In the latter: - the information on size of a specimen remains unchanged;- measurements of size of protoconch do not appear influenced by orientation of plane which cuts it centrally;- the image of knobs and polar tubercle is displayed;- in proximity of passing of the cutting plane through the equatorial one, the image of shape of chambers, growth of whorl and height of marginal line (top of chamber) remain undistorted.1 D/E - ratio of diameter to thickness of nummulite test; T/R - number of chambers counted along a given radius of test; h/l - ratio of height to width of chamber; a - longitudinal diameter of protoconch; b - transversal diameter of protoconch; c - longitudinal diameter of protoconch and deuteroconch