20.500.12556/DiRROS-19206 Signs of crustal extension in Lower Jurassic carbonates from central Slovenia Znaki ekstenzije skorje v spodnjejurskih karbonatih osrednje Slovenije The Lower Jurassic Podbukovje Formation represents a succession of shallow marine carbonate rocks deposited on the former Southern Tethyan Megaplatform and one of its successors, the Adriatic Carbonate Platform. Several outcrops of the Podbukovje Formation from central Slovenia (southern margin of the Ljubljana Moor) are presented, bearing possible evidence of Early Jurassic extensional tectonics. Peritidal facies of the lowermost, Hettangian – Sinemurian, part of the Podbukovje Formation locally interfingers with bodies of matrix supported pervasively dolomitized polymictic breccia, several metres to tens of metres thick and is locally cut by neptunian dykes some few decimetres to metres wide. The same or slightly younger part of the formation locally contains grabens/half-grabens metres to tens of metres deep and filled with poorly sorted pervasively dolomitized matrix supported polymictic breccia. Small miliolid foraminifera are present within the clasts and in the matrix. Finally, partly dolomitized blocky breccia tens of metres thick locally overlies the Pliensbachian – lowermost Toarcian limestone with lithiotid bivalves. Besides completely and partly dolomitized clasts, the breccia contains a variety of limestone clasts and preserves common radial ooids and some bioclasts within the partially dolomitized matrix. The Hettangian-Sinemurian breccias and dykes are presumably related to the early, diffused rifting stage of the Penninic (Alpine Tethys) Ocean, whereas Toarcian breccias relate to the main, focused rifting stage. Together with evolving biota and changing paleo-oceanographic conditions, the extensional tectonics may have been an important factor behind the facies changes observed within the Podbukovje Formation Spodnjejurska Podbukovška formacija predstavlja zaporedje plitvomorskih karbonatnih kamnin, odloženih na nekdanji Južnotetidini karbonatni megaplatformi in Jadranski karbonatni platformi. V članku predstavljamo nekaj izdankov Podbukovške formacije iz osrednje Slovenije (južni rob Ljubljanskega barja), v katerih so vidni možni dokazi za zgodnjejursko ekstenzijsko tektoniko. Periplimski facies najnižjega, hettangijsko-sinemurijskega dela Podbukovške formacije se lokalno prepleta z nekaj metri do nekaj deset metri debelimi plastmi muljasto podprte povsem dolomitizirane polimiktne breče. Drugod plasti periplimskih karbonatov sekajo neptunski dajki, ki so široki do nekaj metrov in zapolnjeni z dolomikritom. Isti ali nekoliko višji deli formacije ponekod vsebujejo tektonske grabne/polgrabne, zapolnjene z nekaj metri ali desetinami metrov povsem dolomitizirane slabo sortirane, muljasto podprte polimiktne breče. V klastih in vezivu so prisotne drobne miliolidne foraminifere. Delno dolomitizirana blokovna breča je prisotna tudi v zgornjih delih Podbukovške formacije nad pliensbachijsko – spodnjetoarcijskim litiotidnim apnencem. Poleg povsem in delno dolomitiziranih klastov breča vsebuje tudi raznolike klaste apnenca. V vezivu so prisotni radialno žarkoviti ooidi in nekaj bioklastov. Hettangijsko–sinemurijske breče in dajke povezujemo z zgodnjo, razpršeno fazo razpiranja Peninskega oceana (Alpske Tetide), toarcijske breče pa z glavno, fokusirano fazo razpiranja. Ekstenzijska tektonika je skupaj z razvojem biote in spremembami v paleo-oceanografskih razmerah pomembno vplivala na faciesne spremembe med nižjimi in višjimi deli Podbukovške formacije. carbonate platform External Dinarides Early Jurassic Podbukovje Formation neptunian dyke breccia karbonatna platforma Zunanji Dinaridi zgodnja jura Podbukovška formacija neptunski dajk breča true false true Geološki zavod Slovenije Angleški jezik Slovenski jezik Neznano 2024-07-09 08:04:24 2024-07-09 08:04:24 2024-07-10 03:52:50 0000-00-00 00:00:00 2024 0 0 str. 25-40 no. 1 vol. 67 2024 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2024-03-29 55 0016-7789 10.5474/geologija.2024.002 198946819 1879-Article_Text-12342527-1-10-20240329.pdf 1879-Article_Text-12342527-1-10-20240329.pdf 1 09404D48B8F236C42099CA83F4DB799B 074c7dca75c1c70cd06427cb6aec3c3617c71c3ac32c186ebf50dd3a6284d034 e87f11b8-3dbb-11ef-b487-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=26442 Geološki zavod Slovenije Geologija 0 0 0