Facies (2005) DOI 10.1007/s10347-005-0038-9 ORIGINAL ARTICLE Jacek Matyszkiewicz · Marcin Krajewski · Jaroslaw K˛ edzierski Origin and evolution of an Upper Jurassic complex of carbonate buildups from Zegarowe Rocks (Krak ´ ow–Wielu ´ n Upland, Poland) Received: 17 February 2005 / Accepted: 14 November 2005 C  Springer-Verlag 2005 Abstract The Upper Jurassic complex of Zegarowe Rocks is situated on the Krak´ ow–Wielu´ n Upland in southern Poland. The complex is dominated by massive lime- stones representing carbonate buildups. The successive stages of carbonate buildup development include: coloni- sation, aggradational growth and progradation phases. In the colonisation phase, on top of loose peloidal-ooid sands micritic peloidal thrombolites developed. Peloidal and ag- glutinated thrombolites and stromatolites proliferated dur- ing the aggradational growth phase, whereas the progra- dation phase was characterised by shallowing and related development of agglutinated stromatolites with coprolites. The latter were the effect of periodical stabilisation of de- trital sediments by microbial mats. The Zegarowe Rocks complex developed upon an elevation of the Late Juras- sic stable northern shelf of the Tethys. This elevation was formed due to local decrease in subsidence rate, induced by the presence of a Palaeozoic granitoid intrusion in the shelf substratum. The carbonate buildups of the Zegarowe Rocks complex, initially developing as sediment-starved mounds upon fault-controlled intraplatform highs under strongly re- stricted background sedimentation rate, were replaced by agglutinated microbial reefs. Keywords Microbialites . Sediment-starved mounds . Agglutinated microbial reefs . Synsedimentary tectonics . Upper Jurassic . Poland Introduction The Krak ´ ow–Wielu´ n Upland is situated in southern Poland, within the Silesian–Krak´ ow Monocline which is built up of Triassic, Jurassic and Cretaceous sedimentary rocks dip- J. Matyszkiewicz () · M. Krajewski · J. K˛ edzierski Department of Geological Cartography, Faculty of Geology, Geophysics and Environmental Protection, University of Science and Technology AGH, al. Mickiewicza 30, 30-059 Krak ´ ow, Poland e-mail: jamat@geol.agh.edu.pl ping gently to the NE. The Krak ´ ow–Wielu´ n Upland forms a ca. 160 km long and 20 km wide belt (Fig. 1A) and rep- resents one of Europe’s famous localities of Upper Jurassic carbonate buildups. The latter build characteristic monad- nocks in the present-day landscape (cf. Alexandrowicz and Alexandrowicz 2003). The Upper Jurassic carbonates of the Krak´ ow–Wielu´ n Upland are of Oxfordian and Kimmerid- gian age (Kutek et al. 1977), and are mostly developed in microbial-sponge facies, in which microbialites are princi- pal rock-forming components that construct complexes of carbonate buildups. The Upper Jurassic microbial megafacies (Gwin- ner 1971; Matyszkiewicz 1999), including numerous microbial-sponge carbonate buildups, developed mainly on the northern shelf of the Tethys and on shelves of the newly opened North Atlantic (Steiger and Jansa 1984; Leinfelder 1993, 1994; Leinfelder et al. 1994, 2002; Our- ribane et al. 2000; Schmid et al. 2001; Mancini et al. 2004). Generally, causes for intensive growth of the Upper Jurassic microbial-sponge carbonate buildups in this area have been satisfactorily explained (Leinfelder et al. 2002). Neverthe- less, in some local settings, these causes may be disputable. It is commonly accepted that carbonate buildups of such type usually developed at the boundary between the middle and deeper parts of a carbonate ramp, following the bedrock topography. One of the causes for growth initiation of carbonate buildups was the presence of a structural high of complex origin, or break of the slope (Trammer 1985; Ellis et al. 1990; Schmid and Jonischkeit 1995; Matyszkiewicz 1997; Leinfelder et al. 2002; Llin´ as 2003; J˛ edrys et al. 2004; Mancini et al. 2004). According to Leinfelder (1994), active synsedimentary tectonics, usually associated with halokinesis, was the main factor favouring development of the Upper Jurassic shallow-water coral reefs growing within a setting strongly contaminated by siliciclastics. In exceptional cases, carbonate buildups developed upon a flat seafloor in deeper parts of the basin. Their origin is explained by the influence of cold seeps or hydrothermal vents (Gaillard et al. 1992; G´ omez-P´ erez 2003). During the Late Jurassic, the Polish fragment of the shelf represented a southward-inclined carbonate ramp.