Calcareous nannofossils and planktic foraminiferal assemblages of ODP Hole 198-1210A

Calcareous nannofossil and planktic foraminiferal assemblages from ODP Hole 1210A in the northwestern Pacific Ocean were used to reconstruct surface-water conditions for the past 500 kyr. Stratigraphic control was provided by calcareous nannofossil events that are thought to be synchronous over a broad range of latitudes. Calcareous nannofossil and planktic foraminiferal assemblages and abundance patterns indicate the unlikelihood of long term (Milankovitch-scale) latitudinal shifts of the Kuroshio Extension over the last 500 kyr and illustrate two successive surface water-mass states, one that prevailed prior to 300 ka and one that existed after 300 ka. The relative abundance of very small placoliths and the absolute abundance of the upper photic zone (UPZ) coccolith species decrease abruptly at approximately 300 ka. The relative abundance of the lower photic zone (LPZ) species Florisphaera profunda greatly increases at the same time, although intervals during which the relative abundance of this taxon is very low or absent also occur prior to 300 ka. The absolute abundance of planktic foraminifera gradually increased after the 300-ka boundary, including peaks of Globoconella inflata. These assemblage and abundance changes suggest significant modifications to the surface water-mass structure. Surface water was weakly stratified prior to 300 ka, but alternated between intensely stratified and vertically mixed after 300 ka. Changes in the surface water-mass structure suggest an intensification of the East Asian summer and winter monsoon after 300 ka

(Table T1) Calcareous nannofossil datum stratigraphic positions and ages of IODP Site 303-U1308

We studied high-resolution Quaternary calcareous nannofossil biostratigraphy to clarify the relationship between nannofossil events and oxygen isotope stratigraphy using the continuous sediment sequence from Integrated Ocean Drilling Program Site U1308 in the North Atlantic Ocean. Results indicate that some nannofossil events found in the section, such as the last occurrences of Reticulofenestra asanoi and Gephyrocapsa spp. (large), are located in a different stratigraphic position compared to previous studies. We also clarify the critical stratigraphic positions of both the first occurrence of Emiliania huxleyi and the last occurrence of Pseudoemiliania lacunosa, which occur just below the highest peaks of each marine isotope Stage 8 and 12

Influence of Heterogeneity on Relative Permeability for CO2/Brine: CT Observations and Numerical Modeling

AbstractThe determination of relative permeability of CO2/brine fluids under reservoir condition is critical for the design of CO2 injection strategy and prediction of CO2 behavior underground through reservoir simulation. For some reservoirs only heterogeneous samples are available for measurement. Heterogeneity, such as layering or cross bedding lamination can commonly be seen in sandstone cores. The effects and mechanism of core-scale heterogeneities on macroscopic scale relative permeability must be well-addressed. Here we report two sets of laboratory core flooding experiments using Berea sandstone for steady-state measurement of relative permeability of CO2/Brine at reservoir condition [1]. Berea sandstone is relatively homogeneous but has strong bedding or lamination structures. Two Berea samples were used (cored along the directions parallel to and perpendicular to the bedding, and named Berea-1 and Berea-2 respectively). We recorded the pressure and discharge volume to get the relative permeability curves for both samples; and utilized the X-ray computed tomography to estimate the distributions of porosity and CO2 (or Brine) saturation for Berea-2. The measured phase relative permeability of Berea-2 sample is greatly deviated from Berea-1. To further investigate the effects of core-scale heterogeneity on the measurement of relative permeability, we carried out a series numerical simulation on core scale using Tough2ECO2N code with building models based on X-ray CT scan images. By comparing the numerical results, we found the heterogeneity of capillary pressure field under one injection direction plays a dominant role in CO2/brine saturation patterns, flow regime and apparent relative permeability model

Diatom events and Neogene nannofossils of ODP Hole 201-1225A

Shipboard investigation of magnetostratigraphy and shore-based investigation of diatoms and calcareous nannofossils were used to identify datum events in sedimentary successions collected at Ocean Drilling Program (ODP) Leg 201 Site 1225. The goal was to extend the magnetic record previously studied at the same site, ODP Leg 138 Site 851, and provide a comprehensive age model for Site 1225. Two high-magnetic intensity zones at 0-70 and 200-255 meters below seafloor (mbsf) were correlated with lithologic Subunits IA and IC in Hole 1225A. Subunit IA (0-70 mbsf) contains the magnetic reversal record until the Cochiti Subchronozone (3.8 Ma) and has a sedimentation rate of 1.7 cm/k.y. This agrees with previous work done at Site 851. Subunit IC (200-255 mbsf) was not sampled at Site 851. Diatom and nannofossil biostratigraphy constrained this subunit, and we found it to contain the magnetic reversal record between Subchrons C4n.2r and C5n.2n (8.6-9.7 Ma), yielding a sedimentation rate of 2.7 cm/k.y. Biostratigraphy was used to establish the sedimentation rates within Subunits IB and ID (70-200 mbsf and 255-300 mbsf, respectively). These subunits had higher sedimentation rates (~3.4 cm/k.y.) and coincide with the late Miocene-early Pliocene biogenic bloom event (4.5-7 Ma) and the Miocene global cooling trend (10-15 Ma). High biogenic productivity associated with these subunits resulted in the pyritization of the magnetic signal. In lithologic Subunit ID, basement flow is another factor that may be altering the magnetic signal; however, the good correlation between the biostratigraphy and magnetostratigraphy indicates that the magnetic record was locked-in near the seafloor and suggests the age model is robust