BIOSTRATIGRAPHY, SEDIMENTOLOGY AND SEQUENCE STRATIGRAPHY OF THE TOURNAISIAN-VISEAN TRANSITIONAL STRATA IN SOUTH CHINA (GUANGXI)

The biostratigraphy and sedimentological evolution of the Tournaisian- Visean (T-V) transitional strata in South China (Guangxi) have been in vestigated. The sediments were deposited on a carbonate platform and i n slope and basinal environments. In the T-V transitional strata, six foraminiferal associations have been distinguished which allow correla tion between the shallow and deep water deposits. A careful examinatio n of the evolutionary stages of the foraminifer Eoparastaffella provid es a more accurate criterion for the definition of the T-V boundary, b ut does not significantly modify the historical one. The distinction o f two morphotypes is based on the elevation of the last whorl and the peripheral outline. Tournaisian specimens of Eoparastaffella have a we ll rounded periphery (morphotype 1) contrasting with the subangular pe riphery of younger Visean specimens (morphotype 2). A coefficient can be deduced from simple biometric measurements for more precisely defin ing the T-V boundary. The sequence stratigraphy of the T-V strata in S outh China has been reconstructed by combining biostratigraphical and sedimentological data. It allowed the correlation of the T-V transitio nal strata between the platform area and the slope and basinal locatio ns. Late Tournaisian strata were deposited during a highstand systems tract. Near the end of the Tournaisian, a major drop in relative sea-l evel led to the development of an unconformity in the platform area. L owstand deposits formed during latest Tournaisian time in the basin wh ere a detailed biostratigraphic framework has been devised. Sediments deposited during the ensuing transgressive systems tract overlie the l ate Tournaisian highstand sediments in the platform area and the lates t Tournaisian lowstand deposits in the basin. A major drop in relative sea-level near the end of the Tournaisian has been recognized worldwi de. Therefore, the possibility of using the sequence stratigraphy of t he T-V strata in South China for worldwide correlations should be inve stigated. (C) 1997 John Wiley & Sons, Ltd.