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Winterer, E.L., Sager, W.W., Firth, J.V., and Sinton, J.M. (Eds.), 1995Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 14332. EARLY CRETACEOUS SHALLOW-WATER BENTHIC FORAMINIFERSAND FECAL PELLETS FROM LEG 143 COMPARED WITH COEVAL FAUNASFROM THE PACIFIC BASIN, CENTRAL AMERICA, AND THE TETHYS1Annie Arnaud-Vanneau2 and William V. Sliter3ABSTRACTEarly Cretaceous shallow-water benthic foraminifers and fecal pellets were recovered from Allison and Resolution guyots inthe western Mid-Pacific Mountains (MPM) during Ocean Drilling Program Leg 143. These faunas are used to date the carbonateplatform owing to the near absence of other microfossils. Four sites contained the Early Cretaceous assemblages: Site 865 onAllison Guyot, and Sites 866, 867, and 868, which were drilled as part of a transect across the perimeter of Resolution Guyot.Of these sites, Site 866, located about 1.5 km inward from the perimeter mound on Resolution Guyot, provided the mostcomplete record of carbonate sedimentation because drilling penetrated about 1600 m of Hauteri vian to late Albian shallow-watercarbonate rocks capped by a thin veneer of Maastrichtian to Pliocene pelagic sediments before encountering basalt. The Hau-terivian age of the basal limestone pre-dates the clastic limestone of Barremian age from Deep Sea Drilling Project Site 463 in theMPM and thus represents the oldest shallow-water carbonate rocks yet recovered from the Pacific Basin.Forty-four species of benthic foraminifers, including the new species Nezzazata isabellae and Vercorsella wintered, and threespecies of fecal pellets are grouped into five biostratigraphically significant assemblages: Assemblage I = late Albian, AssemblageII = middle(?) to late Albian(?). Assemblage III = late Aptian(?) to early Albian(?), Assemblage IV = Barremian to early Aptian,and Assemblage V = Hauterivian. This biostratigraphic succession served as the standard for dating and comparing the Aptian(?)-to-Albian sequence at Site 865 and the Albian sediments at Sites 867/868, as well as the Aptian-to-Albian shallow-water sequencesdrilled during Leg 144.Although sparse, the Hauterivian to Aptian assemblages represent a mixture of species known from the northern and southernmargins of the Tethys. Further, the stratigraphic succession of the Pacific species is the same as that in Tethyan sequences. Late Aptianto Albian assemblages are distinguished by an influx of species from Mexico and Venezuela associated with a Tethyan fauna.Based on the benthic faunas, three major paleoenvironments corresponding to the development of the platform are recognizedat Site 866: (1) sandy, normal-marine conditions in the Hauterivian, (2) restricted lagoonal conditions with stromatolites duringthe Barremian to early Aptian, and (3) muddy facies with sponges and normal-marine lagoonal conditions during the late Aptianand Albian.INTRODUCTIONEarly Cretaceous benthic foraminifers were recovered from shal-low-water limestone drilled in the western Mid-Pacific Mountains(MPM) at Allison Guyot (Site 865) and Resolution Guyot (Sites 866and 867/868) during Leg 143 (Fig. 1). The MPM comprise severalbroad plateaus surmounted by flat-topped seamounts or "guyots" ofknown Cretaceous age (Hamilton, 1956; Heezen et al., 1973; Matthewset al., 1974). Drilling during Leg 143 was conducted to determine thehistory of Cretaceous volcanism and subsequent carbonate platformdevelopment for guyots in the western central Pacific Ocean. Accord-ingly, Resolution Guyot, a multiple-reentry site, was drilled to extendthrough the carbonate cap and into the volcanic pedestal, whereasAllison Guyot, a single-bit site, was drilled into the cap.Site 865 is located on the summit of Allison Guyot in the centralMPM at 18°26.41'N, 179°33.34'W and a water depth of 1518.4 mbsf.About 731 m of Lower Cretaceous shallow-water limestone was drilledbefore basalt sills were encountered in the lowest 33 m of Hole 865A.The remaining three sites were drilled on Resolution Guyot in thewestern MPM as part of a transect across the perimeter of a MPMguyot. Site 866 was located on the northern rim of the summit about1.5 km inward from the perimeter mound at 21° 19.95'N, 174°18.84'Eat a water depth of 1361.8 mbsf so as to penetrate lagoonal facies.' Winterer, E.L., Sager, W.W., Firth, J.V., and Sinton, J.M. (Eds.), 1995. Proc. ODP,Sci. Results, 143: College Station, TX (Ocean Drilling Program).Institut Dolomieu, Rue Maurice Gignoux, 38031 Grenoble Cedex, France. U.S.Geological Survey, 345 Middlefield Road, Ms 915, Menlo Park, CA 94025, U.S.A.About 1600 m of Lower Cretaceous shallow-water limestone restingon basalt was drilled in Hole 866A; drilling extended 124 m fartherinto the basalt. Sites 867 and 868, located about 2 km northward ofSite 866 and only about 400 m apart, were positioned for drilling intothe summit of the perimeter mound (Site 867) and a lower terraceoutside the mound (Site 868). Site 867, drilled at 21°20.96'N,174°18.58'E at a water depth of 1352 mbsl, penetrated about 77 m ofLower Cretaceous shallow-water limestone. At Site 868, located at21°21.17'N, 174°18.56'E and a water depth of 1385 mbsl, only about17 m of Lower Cretaceous shallow-water limestone was penetrated.Most of the biostratigraphy of the Lower Cretaceous shallow-watercarbonates recovered from Leg 143 is based on benthic foraminifersowing to the near absence of planktonic foraminifers, calcareousnannofossils, and palynomorphs. Rudist bivalves represent an impor-tant biostratigraphic component of the biologic assemblage from Leg143, but their occurrence is surprisingly rare and patchy at Allison andResolution guyots and consists mostly of fragmental debris (see Masseand Swinburn, this volume). Accordingly, we present here the distri-bution and taxonomy of the biostratigraphically important Early Cre-taceous benthic foraminifers and fecal pellets recovered, discuss theinterpretation of their ages, and draw comparisons among these spe-cies, many of which are new or are previously undescribed from thePacific Basin, and comparable species from well-known assemblageselsewhere. Our study focuses on Sites 865 and 866, the latter repre-senting the oldest and most complete record from Leg 143 and, indeed,the oldest shallow-water carbonates yet recovered from the PacificBasin. The stratigraphic distribution of benthic foraminifers and fecalpellets in Holes 865A and 866A is shown in Tables 1 and 2; mostspecies are illustrated in Plates 1 through


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