The radiation of early Carboniferous foraminifers and rugose corals following the Devonian–Carboniferous crisis offers the best tool for high-resolution correlations in the Mississippian, together with the conodonts in the Tournaisian, notably in the Namur–Dinant Basin. However, some of the guides are facies-controlled and an integrated approach combining biostratigraphy, sedimentology and sequence stratigraphy is critical to identify delayed entries, potential stratigraphic gaps and to avoid diachronous correlations. The main difficulty is in correlating shallow and deeper water facies at any given time. In existing zonations, the Viséan part of the scheme is always more detailed, reflecting the widespread development of shallow-water platforms in the early Viséan which created conditions more suitable for foraminifers and rugose corals over large areas. In contrast, the Tournaisian zones, less well documented, reflect unfavourable environmental conditions in the lower ramp (Dinant Sedimentation Area) and pervasive dolomitization of the inner ramp (Condroz and Namur Sedimentation Areas). Recent progress in understanding the Belgian early Carboniferous sequence stratigraphy and lithostratigraphy, and revision of the biostratigraphy of the key sections, strongly modify former biostratigraphic interpretations. Improvements mainly concern the latest Devonian, the late Tournaisian and the early Viséan. The late Devonian and the Tournaisian are equated with foraminifer zones DFZ1 to DFZ8 and MFZ1 to MFZ8 respectively. The Viséan correlates with zones MFZ9 to MFZ14. Zone MFZ15 straddles the Viséan–Namurian boundary and Zone MFZ16 is the youngest Mississippian zone. The rugose corals allow the recognition of ten zones, RC0 to RC9, covering the Strunian (late Famennian) to Serpukhovian interval. Discrepancies with former zonations are discussed. The Moliniacian Stage is emended to restore the coincidence between its base and that of the Viséan.
The relative influences of local tectonics and global eustasy in the architecture of the sedimentary units of the Namur-Dinant Basin (southern Belgium) are determined. Nine third-order sequences are recognised. During the Lower Tournaisian (Hastarian and lower Ivorian) a homoclinal ramp extended from southern Belgium through southern England (Mendips) and into southern Ireland. From the upper Ivorian to the lower Visean rapid facies changes occurred due to progradation and increasing prominence of Waulsortian mudmounds. Progradation gradually produced a situation in which inner shelf facies covered the Namur (NSA), Condroz (CSA) and southern Avesnes (ASA) sedimentation areas, whereas outer shelf facies were restricted to the Dinant sedimentation area (DSA). During the middle and late Visean a broad shelf was established from western Germany to southern Ireland. Because the shelf built up mainly by aggradation, parasequences can be followed over a large area. An early phase of Variscan shortening is perceptible during the Livian. The stratigraphic gap between the first Namurian sediments (E2 Goniatite Zone) and the underlying Visean varies from place to place, but is more important in the north.
The Tournaisian and Viséan were formerly considered as series and in Belgium were divided into two (Hastarian and Ivorian) and three stages (Moliniacian, Livian and Warnantian), which are now considered as substages. The Belgian substages are based on conodonts and foraminifers, and incidentally on rugose corals, and are described here. Their boundaries, biostratigraphy and sequence stratigraphy are well detailed and clearly defined. The base of the Hastarian (lower Tournaisian) corresponds to the base of the Tournaisian (base of Carboniferous); the base of the Ivorian (upper Tournaisian) corresponds to the appearance of the conodont Polygnathus communis carina, a little above the last Siphonodella; the base of the Moliniacian (lower Viséan) corresponds to the base of the Viséan stage defined by the first occurrence of the foraminifer Eoparastaffella simplex; the Livian (middle Viséan) corresponds to the foraminiferal MFZ12 Zone and is marked by the appearance of Koskinotextularia and Pojarkovella nibelis; the base of the Warnantian (upper Viséan) is marked by the appearance of Neoarchaediscus, Vissariotaxis, Planospirodiscus, and Palaeotextularia with a bilaminar wall, the index taxa of the MFZ13-Neoarchaediscus Zone. The up-to-date chronostratigraphic subdivision of the Tournaisian and Viséan is not limited to Belgium and the surrounding areas. It can be applied through Eurasia as far as South China. The Belgian units could therefore be the basis for a future international division of the Tournaisian into two parts (Hastarian and Ivorian) and of the Viséan into three parts (Moliniacian, Livian and Warnantian), corresponding to time intervals of c. 5–8 Ma.
The first appearance of Eoparastaffella simplex in the lineage Eoparastaffella ovalis-Eoparastaffella simplex (foraminifers) has been officially approved by the Voting Members of the SCCS in early 2002 as the new biostratigraphic criterion to define the base of the Viséan. The present paper summarizes eight years of research and proposes a new Global Stratotype Section and Point from Guangxi, South China. The boundary is defined at the base of bed 85 of the Pengchong section where the first E. simplex is recorded, following more primitive Eoparastaffella. The conodont Gnathodus homopunctatus, whose cryptic first appearance has been used as an empirical tool for identification of the TV boundary in Western Europe, enters a decimetre higher in bed 86. Scaliognathus anchoralis europensis and other conodonts considered characteristic of the late Tournaisian occur below these levels.
The biostratigraphy and sedimentological evolution of the Tournaisian±Vise an (T±V) transitional strata in South China (Guangxi) have been investigated. The sediments were deposited on a carbonate platform and in slope and basinal environments. In the T±V transitional strata, six foraminiferal associations have been distinguished which allow correlation between the shallow and deep water deposits. A careful examination of the evolutionary stages of the foraminifer Eoparastaella provides a more accurate criterion for the de®nition of the T±V boundary, but does not signi®cantly modify the historical one. The distinction of two morphotypes is based on the elevation of the last whorl and the peripheral outline. Tournaisian specimens of Eoparastaella have a well rounded periphery (morphotype 1) contrasting with the subangular periphery of younger Vise an specimens (morphotype 2). A coecient can be deduced from simple biometric measurements for more precisely de®ning the T±V boundary.The sequence stratigraphy of the T±V strata in South China has been reconstructed by combining biostratigraphical and sedimentological data. It allowed the correlation of the T±V transitional strata between the platform area and the slope and basinal locations. Late Tournaisian strata were deposited during a highstand systems tract. Near the end of the Tournaisian, a major drop in relative sea-level led to the development of an unconformity in the platform area. Lowstand deposits formed during latest Tournaisian time in the basin where a detailed biostratigraphic framework has been devised. Sediments deposited during the ensuing transgressive systems tract overlie the late Tournaisian highstand sediments in the platform area and the latest Tournaisian lowstand deposits in the basin. A major drop in relative sea-level near the end of the Tournaisian has been recognized worldwide. Therefore, the possibility of using the sequence stratigraphy of the T±V strata in South China for worldwide correlations should be investigated.
Six paleogeographic sedimentation areas (s. a.) are recognized in the Namur-Dinant Basin: (1) the Hainaut s. a., (2) the Namur s. a., (3) the Condroz s. a., (4) the Dinant s. a., (5) the Visé-Maastricht s. a., and (6) the southern Avesnois s. a. (only in northern France). Together with the sea-level variations (third-order sequences), local controls influenced the nature of the sedimentary deposits, so the lithostratigraphic successions in each sedimentation area are distinctive. The depositional setting was that of a carbonate platform which evolved from a ramp in the early Tournaisian to a rimmed shelf during the early Viséan and then to a regionally extensive shelf during the middle and late Viséan. Before the Livian, open marine fades were developed to the south, but from the Livian onwards open marine facies were restricted to the north while evaporites developed in the south. This inversion of the normal pattern was probably related to an early phase of Variscan shortening. Dinantian biostratigraphy is mainly based upon foraminifera, rugose corals and conodonts. Fifty formations (including members), 3 groups and 2 informal lithostratigraphic units are briefly described.
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