PALEOGEOGRAPHY OF THE WESTERN PELAGONIAN CONTINENTAL-MARGIN IN BEOTIA(GREECE) DURING THE CRETACEOUS-BIOSTRATIGRAPHY AND ISOTOPIC COMPOSITIONS (DELTA-C-13,DELTA-O-18) OF CALCAREOUS DEPOSITS

The palaeogeography of Beotia, Greece, during the Cretaceous is outlin ed on the basis of biostratigraphic evidence derived predominantly fro m the distribution of rudist bivalves and planktonic foraminifera. Obs erved facies trends are evaluated together with carbon and oxygen isot opic compositions of limestones and rudist shells. The interaction bet ween global sea level fluctuations and gradual subsidence of the Pelag onian continental margin controlled facies distribution during most of the Cretaceous. The sedimentary record begins with Berriasian flysch- type deposits that accumulated during incipient Eohellenian orogenic m ovements. Barremian deposits with similar sedimentological characteris tics probably belong to the same tectonostratigraphic unit. During Apt ian-Cenomanian times, terrigenous clastics with a few intercalated mar ine limestones accumulated in South Beotia. The fossil content of patc h reefs presents important biostratigraphic marks in this terrigenous sequence. Carbon and oxygen isotopic compositions recorded unstable ma rine environments and subsequent decrease of continental influx. Conti nuous subsidence and rising sea levels are evident in the Late Turonia n onlap of rudist limestones on the Eohellenian basement of the Ptoon Mountains as well as in the interfingering of calcareous slope deposit s and basinal Globotruncana-mudstones of South Beotia. During Late Con iacian-Early Santonian, a marked regression finally led to a regional emersion and the development of a karst relief. This regression is pre dated by ''heavy'' oxygen isotopic compositions in the Coniacian limes tones, which probably resulted from isolation of a larger marine embay ment from oceanic circulation. The subsequent Late Santonian-Campanian transgression flooded all of Beotia. Its sediments lie over allochtho nous laterites. Extended rudist biostromes developed as soon as contin ental influx ceased, as indicated both by the stable isotope compositi ons of rudist shells and embedding limestones. During the Late Campani an, the rather uniform platform-type depositional environments differe ntiated and pelagic sedimentation recurred in South Beotia, whereas de positional environments to the north remained shallow. Incipient tecto nic movements were responsible for a Late Maastrichtian emersion of No rth Beotia, while basinal conditions persisted in the south. The onset of flysch-type sedimentation occurred simultaneously during the Late Paleocene in North Beotia, as well as in the adjacent Parnassus and Pi ndos zones. However, this important facies transition has not yet been precisely dated in South Beotia.