Organic matter maturation vs clay mineralogy: A comparison for Carboniferous to Eocene sediments from the Alpine – Dinaride junction (Slovenia, Austria)

Thomas Rainer,Reinhard F Sachsenhofer,Gerd Rantitsch,Uroš Herlec,Marko Vrabec

doi:10.5474/geologija.2002.057

Abstract

Clay mineral diagenesis of Carboniferous to Paleogene rocks within the Alpine-Dinaric junction was studied and compared to vitrinite reflectance. Generally, there is a good fit between clay mineral diagenesis and VR. However, clay mineral alterations lag behind maturation in some Ladinian and Camian rocks (e.g. northern margin of the Dinaric Platform). Most probably, the lag in clay mineral diagenesis reflects an highly varying geochemical background in these stratigraphic horizons. Carboniferous deposits are late diagenetic to anchimetamorphic. Mesozoic deposits cover the range from middle diagenesis to the anchizone. Triassic to Cretaceous rocks in the SB and the Sava Folds reach the anchizone. Differences in diagenesis/metamorphism are mainly due to different maximum burial in Paleogene time.

Highlights

Correlations between inorganic and organic thermal indicators have been discussed by many authors (e.g. Kisch, 1987; Underwood et al, 1992; Sachsenhofer et al, 1998)
These papers show that a universal statistical correlation between Vitrinite Reflectance (VR) and Illite “Crystallinity” (IC) cannot be established, because the two indices respond to different sets of variables
The present paper provides a comparison between organic and inorganic indicators of diagenesis to anchimetamorphism in the Alpine-Dinaric transition zone

Summary

Introduction

Correlations between inorganic and organic thermal indicators have been discussed by many authors (e.g. Kisch , 1987; Underwood et al, 1992; Sachsenhofer et al, 1998). Kisch , 1987; Underwood et al, 1992; Sachsenhofer et al, 1998) These papers show that a universal statistical correlation between Vitrinite Reflectance (VR) and Illite “Crystallinity” (IC) cannot be established, because the two indices respond to different sets of variables. The Eastern Alps are situated north of the Periadriatic Lineament (PL), whereas the Southern Alps and the Dinarides occur south of it (Fig. 1). Within the Southern Alps and the Dinarides, the pre-Variscan sedimentary cycle is terminated by Lower Carboniferous flysch. During the Ladinian the uniform carbonate platform disintegrated and the Slovenian Basin (SB) formed between the Julian carbonate platform (CP) to the north and the Dinaric CP to the south ( Buser , 1987). From the Late Miocene onward the Southern Alps were affected by SSE vergent „Alpine“ thrusting ( Castellarin & Cantelli , 2000)

Methods

Results and Discussion

Conclusions