Abstract

The Middle to Upper Devonian sequence of the Holy Cross Mts, Central Poland, contains several cycles of eustatic origin. Four depositional cycles were identified in the Givetian to Frasnian stromatoporoid-coral limestones of the SW part of the shallow water Kielce region; only one appears to have been controlled by local epeirogeny. Deepening pulses were accompanied by typical intermittent drowning of carbonate shelf and recorded in sequential replacement of habitat types from platform to bank- to reef-complex and widespread biatic migrations, both intra-regional (i.e., from the adjacent Lysogory basin) and extra-regional. There are no evident breaks in the biotic succession after extensive regional colonization of newly established (after dolomitic phase) suitable platform habitats. Particular groups show differentiated developmental trends, but a two-step terminal extinction event is recognizable in the disappearance of the time-specific (Givetian-type) worldwide undifferentiated biostromal banks. This seems to be the result of the shelf ecosystem de-stabilization by successive regressive-transgressive pulses; the step-by-step pattern of bioevents obscures a natural base for definition of the Middle/Upper Devonian boundary. Flourishing of new communities after some biotic stagnation is associated with creation of peculiar reef biotopes after basal Frasnian transgression. The Holy Cross part of the shelf was a rather important endemism centre associated with semi-isolated parts of the Givetian platform and with Frasnian buildups, in spite of the generally transitional biogeographical aspect between Western and Eastern Europe.