Emendation of the Grivska formation in its type area (Dinaridic Ophiolite Belt, SW Serbia)

Milan Sudar,Hans-Jürgen Gawlick

doi:10.2298/gabp1879001s

Abstract

Age, microfacies and depositional realm of the Grivska Formation is controversially discussed due to the fact that detailed investigations are missing. Based on reinvestigations of the type locality of the Grivska Formation and in adjacent areas, the following results can be drawn: 1) The Grivska Formation is of Late Triassic (Early Carnian to Rhaetian) age according to conodont dating. 2) Sedimentological and microfacies studies evidenced that the Grivska Formation was deposited on the continental slope and transitional to the Neo-Tethys Ocean. Based on the results of these investigations in the type area and several reference sections in the Dinaridic Ophiolite Belt, the Grivska Formation is emended and clearly defined. In the Dinaridic Ophiolite Belt, the Grivska Formation occurs only as clasts and blocks in the ophiolitic melange.

Highlights

Grey cherty limestone sequences occur quite common in the Triassic and Jurassic sedimentary successions of the Western Tethys realm: similar depositional and diagenetic conditions led to the formation of grey cherty limestones elsewhere
The reinvestigation of the type area around the village Grivska and in adjacent areas (GAWLICK et al, 2016b, 2017a) and this contribution points out, that 1) All cherty limestone successions in the type area have a Late Triassic (Early Carnian to Rhaetian) age, 2) The cherty limestones in the type area occur as blocks in the ophiolitic mélange, 3) The microfacies of all cherty limestones is characterized by radiolarian- and filament-bearing wackestones; only occasionally fine-grained turbiditic limestone intercalations occur
The distal shelf area is characterized by the deposition of a Hallstatt Limestone sequence as typical elsewhere (e.g., KRYSTYN, 2008; GAWLICK et al, 2017a, b) and grey cherty limestone were deposited on the continental slope and the proximal parts of the oceanic domain

Summary

Introduction

Grey cherty limestone sequences occur quite common in the Triassic and Jurassic sedimentary successions of the Western Tethys realm: similar depositional and diagenetic conditions led to the formation of grey cherty limestones elsewhere. To ?Middle Norian dm-bedded cherty limestones, occasionally the beds are amalgamated Along both sides of the Lim river, a large block of the Grivska Formation underlain and overlain by the ophiolitic mélange is preserved with huge slump deposits in all stratigraphic levels. Lithology: Generally thin- to medium-bedded micritic grey cherty limestones, typically of radiolarian wackestone microfacies with rare filaments The Late Triassic successions in the eastern regions of the East Bosnian-Durmitor Megaunit (Lim Unit) e.g., Sutjeska canyon in the vicinity of Rudo (SUDAR, unpublished data) and in the Gradac area around Pljevlja (SUDAR 1986) are not investigated in detail Whether these grey cherty limestone sequences are part of the Grivska Formation or they belong to other formations can only be decided after detailed stratigraphic and microfacies studies. These successions belong to the parautochthonous basement of the Dinaridic Ophiolite Belt with completely different under- and overlying sedimentary sequences

Discussion

Conclusions