Elementy paleogeografii późnodewońskiej w rejonie przybrzeżnym szelfu południowej Polski

Abstract

MAJOR FEATURES OF THE LATE DEVON.IAN PALEOGEOGRAPHY IN THE NEAR-SHORE SHELF AREA OF SOUTHERN POLAND Summary The Devonian shallow extracratonic basin in southern Poland was bordered to the south by the pre-Carpathian land mass, and to the west it sloped into deep geosynclinal basin (Fig. 1 ). During the Late Devonian times this tropical shelf sea was characterized by clearly diversified bottom morphology. In the early Frasnian, isolated subtidal elevations were formed by organic buildups of coral-stromatoporoid mud-mound type. A short-lived regressive pulse (Lower gigas Zone) brought these structures to wave-agitated zone where they probably developed as true pinnacle reefs. During most of the Late Devonian times the regressive conditions prevailed enabling near-shore platforms to develop and prograde basinwards to the north (Fig. 3). These attached carbonate platforms shed biodetrital and intraclastic material into the adjoining parts of the shelf basin via storm currents (tempestites) and, subordinately, turbidite currents. Depositional environment of the shelf basin was controlled mainly by bathymetry (below the optimum zone of biogenie CaCO3 production: i.e. below 50-100 m), and changing degree of stagnation with concomitant fluctuations in oxygen regime (according to the model by W.C. Byers).