Neptunian dykes in the Middle Miocene reefs of western Ukraine: preliminary results

Abstract

Nep tu nian dykes were re cently re corded within the Mid dle Mio cene (Up per Badenian and Lower Sarmatian) Medobory reef com plex of the Carpathian Fore land in west ern Ukraine. The Up per Badenian reefs are cut by a reg u lar, semi-per pen dic u lar net work of in ter sect ing fis sures that pen e trate the Badenian reef lime stone down for more than 10 m. The dykes are filled by sev eral gen er a tions of Sarmatian microbialites coat ing the frac ture walls and by bed ded bioclastic sed i ment (in clud ing foraminifers) which is more im por tant vol u met rically. The fis sure fill ings con tain ing both the Sarmatian ma te rial as well as rare clasts of Badenian rocks in di cate that the fis sures were open dur ing the on set of Sarmatian de po si tion. They orig i nated fol low ing the emer gence and frac tur ing of the Badenian lime stones, either due to fault tec ton ics at ba sin mar gins in duced by ba sin sub si dence, around the Badenian-Sarmatian bound ary, or to grav i ta tional insta bil ity of large lithified Badenian reef bod ies. Only one phase of frac ture open ing oc curred. The fill ing of frac tures was ep i sodic, with pulses of ce men ta tion and mi cro bial growth and sed i ment in jec tion. Four dif fer ent foraminiferal as sem blages re corded in the nep tu nian dykes in di cate that the pro cess of frac ture fill ing was long-last ing. Re search In sti tute, Rakowiecka 4, Po land, tadeusz.peryt@pgi.gov.pl; Danuta Peryt, In sti tute of Paleobiology, Pol ish Acad emy of Sci ences, Twarda 51/55, 00-818 Warszawa, Po land, e-mail: d.peryt@twarda.pan.pl (re ceived: Oc to ber 26, 2012; ac cepted: De cem ber 3, 2012; first pub lished on line: De cem ber 14, 2012). Marek Jasionowski and Tadeusz Marek Peryt, Pol ish Geo log i cal In sti tute -Na tional

Bryoherms from the lower Sarmatian (upper Serravallian, Middle Miocene) of the Central Paratethys

“…In the Eastern Paratethys the best studied reefs occur in the Ukrainian Medobory Hills (Saint Martin and Pestrea 1999 ; Jasionowski 2006 ; Taylor et al 2006 ; Studencka and Jasionowski 2011 ; Jasionowski et al 2006 ; Górka et al 2012 ) and on the Kertsch and Taman peninsulas (Abich 1865 ; Andrussow 1909 ; Goncharova and Rostovtseva 2009 ). The reefs in the Medobory Hills are called ‘serpulid–microbialite reefs’ but microbialites dominate by far and serpulid tubes and bryozoa are subordinate (e.g., Jasionowski 2006 ; Górka et al 2012 ).…”