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Development and chronology of the Late Jurassic shallow-water carbonate deposits of the Holy Cross Mountains area, central Poland

Wierzbowski Andrzej

Volumina Jurassica

2023

Vol. 21

39--82

The Late Jurassic shallow-water carbonates with intervening clayey-marly deeper-water deposits in the Holy Cross Mts. area formed over large bank of the elevated part of the Northern Tethyan Shelf during about 12 myr. They comprise three main successions (I, II and III) deposited partly in different environmental conditions, controlled by tectonic and climatic factors, and still preserved in the north-eastern margin, the north-western margin and the south-western margin of the Holy Cross Mountains. The history of sedimentation is presented according to the concept of the large tectono-stratigraphic units COK, LUK and KVB, which owe their origin to variable rates of tectonic subsidence, as introduced by Kutek (1994) for the area of central Poland. The studied deposits of the COK megasequence cor- responding to the Upper Oxfordian and the Lower Kimmeridgian up to the Hypselocyclum Zone consist of coral limestones, various grained (including oolitic) limestones, and micritic limestones formed over the gradually enlarging shallow-water carbonate platform of the Holy Cross Mts. This platform was subsequently subdivided into two elevated areas, separated by a depressed zone in the middle, bounded by the Nowe Miasto–Iłża–Bałtów Fault Zone in the north-east and the Holy Cross Fault System in the south. The younger mega- sequence LUK with it strongly transgressive character marks the successive stages of the marine transgression which entered the central, lowered part of the area of the Holy Cross Mts. from the west, where it appeared already in the early Hypselocyclum Chron. It succes- sively spread across the Holy Cross Mts. area towards the north-east and south bringing everywhere the deposition of various oyster lu- machelles and marls with ammonites at the end of the Hypselocyclum Chron and during the Divisum Chron of the Early Kimmeridgian to the Acanthicum/Mutabilis Chron of the earliest Late Kimmeridgian. The following megasequence KVB is represented by the detrital lu- machelles and chalky limestones with nereineids of the Eudoxus Chron of the Late Kimmeridgian marking the development of still younger shallow-water carbonate platform in the uplifted areas in the north-eastern and possibly the south-western margins of the moun- tains, allegedly subdivided by a deeper area of sedimentation of marly deposits. The youngest Late Jurassic deposits of the Holy Cross Mts., are very fragmentarily preserved, mostly because of Early Cretaceous uplift and erosion. They suggest an initial episode of complete drowning of the carbonate platform which became covered by marly deposits during the Early Tithonian, and the subsequent restoration of shallow-water carbonate sedimentation at the end of the Early Tithonian.

The Kimmeridgian of the south-western margin of the Holy Cross Mts., central Poland: stratigraphy and facies development. Part I. From deep-neritic sponge megafacies to shallow water carbonates

Wierzbowski Andrzej

Volumina Jurassica

2020

Vol. 18, no. 2

161-234

The stratigraphical interval of the Kimmeridgian between the Bimammatum and the Hypselocylum zones in the SW margin of the Holy Cross Mts. shows a transition from the open shelf deep-neritic sponge megafacies to the shallow-water carbonate platform, including its development and decline. The uniform progradation of the shallow-water carbonate platform occurred at the end of the Planula Chron. Development of the shallow-water carbonate platform was controlled by climatic and tectonic factors. The former induced by orbital cyclicity resulted in changes of sea-level, revealed i.a. by the incoming of open-marine ammonite faunas, the latter were related to the synsedimentary activity of faults which resulted in contrasted facies changes. The episodically occurring strong influx of siliciclastic material was at least partly controlled by the tectonic activity. The newly elaborated formal lithostratigraphic subdivision takes into account the facies development of the succession in relation to climatically and tectonically induced changes. Such is e.g. the Małogoszcz Oolite Formation, corresponding to a single 100-kyr eccentricity cycle from the late Platynota Chron to the earliest Hypselocyclum Chron, bordered from the base and top by two transgressive climatically-controlled levels. The final stage of the shallow-water platform development at the end of the Hypselocyclum Chron was marked by the successive limitation of restricted environments, and the appearance of more open-marine conditions related to tectonic subsidence of the area of study. Comparison between the carbonate platform development of the Holy Cross Mts. in central Poland, and the coeval shallow-water carbonates of the Jura Mts. in northern Switzerland and south-eastern France provides an opportunity to consider similarities in the successions which can be attributed to the climatically-controlled sedimentary cyclicity and/or the wide-ranged tectonic phenomena. The palaeontological part of the study gives comments on the classification and phylogeny of ammonites of the families Ataxioceratidae and Aulacostephanidae.