Lead and zinc ores of the Alpine Triassic occur mainly within shallow water sediments of lower Carnian age; these sequences underwent emersion periods and were affected by weathering and meteoric karstification (Lagny, 1975; Bechstadt, 1975a, b, 1979; Assereto et al, 1976).
The Bleiberg-Kreuth mineralization within the Wetterstein limestone is controlled by at least four geologic factors: (1) it occurs on lagoonal platforms, situated some distance from the mainland to the north, which might have been the original source of the metal; (2) on these platforms it is localized within areas where an extensive cavity network had been formed by karstic weathering; (3) the mineralization is bound to areas close to or with peritidal cyclic and evaporitic sedimentation (“special facies” of Schneider, 1964); and (4) it occurs below sealing shales (Raibl beds).
Only the subaerial exposure facies is described in more detail, whereas the conflicting theories concerning lead-zinc mineralization are mentioned only briefly (Figs. 1,2).
Figures & Tables
Carbonate Depositional Environments
For more than 100 years geologists have been ex amining and describing modern sediments with an eye toward using characteristic features to aid in the interpretation of depositional settings of ancient strata. This field of interest developed particularly during the 1950s and 1960s with the creation of detailed models for modern carbonate deposition in Florida, the Bahamas, Cuba, the Persian Gulf, Belize, Pacific atolls, the Great Barrier Reef and other areas. An understanding of the depositional environments of these modern models, coupled with increased understanding of diagenetic effects, has led to vastly improved interpretations of ancient limestones. Such models also improved the “predictability” of many carbonate reservoir rocks.
In spite of the great strides made in our knowledge about carbonate depositional environments, their characteristic features have never been synthesized in a single work. Although excellent textbooks exist which describe some aspects of the interpretation of both ancient strata and modern sediments, systematic treatment of the entire subject is available only in the primary literature.
This book is an attempt to bring together this widely disseminated literature. The volume is specifically designed for use by the non—specialist-the petroleum geologist or field geologist—who needs to use carbonate depositional environments in facies reconstructions and environmental interpretations. Yet it is hoped that the book will also serve as a valuable reference for the specialist or advanced graduate student.
Toward that purpose, the book is extensively illustrated with color diagrams and photographs of sedimentary structures and facies assemblages. The text focuses on the recognition of depositional environments rather than on the hydrodynamic mechanisms of sediment movement.