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We propose a theoretical model based on the concept of multiferroic tunnel junction. The model is capable of producing eight different logic states by combining the spin-filter effect and the screening of polarization charges between two electrodes through a general spintronic tunneling. The dependence of the conductance ratio with very large magnitude on electric polarization, exchange splitting, barrier width, and bias voltage is investigated. The result may provide some insights into the realization of octal data storage namely, the eight different logic states are used as octal code, which could lead to the tremendous increase of memory storage density. © 2007 American Institute of Physics. DOI: 10.1063/1.2768075

Miocene sediments of the Caribbean Gatun and Chagres formations, Panama Canal basin, were deposited within an archipelagic strait that connected Caribbean and Pacific waters. Shallow-water (∼ 25 m) benthic foraminifera of the Gatun Formation have a strong Caribbean affinity, indicating that a significant interoceanic, biogeographic barrier had formed at ∼ 8 Ma. However, benthic foraminifera of the overlying Chagres Formation are bathyal and markedly Pacific in affinity, indicating that at ∼ 6 Ma, waters of the Panama isthmian strait deepened to ∼ 200–500 m and Pacific bathyal waters flowed into the Caribbean. The Chagres Formation crops out at the Caribbean entrance to the Panama Canal in a large wedge of cross-laminated sandstone and coquina. The cross-laminations and coarse grain size indicate high-energy currents atypical of bathyal settings. We infer that a jet of the Pacific North Equatorial Countercurrent–Equatorial Undercurrent passed through the Panama isthmian strait to deposit these sediments on the Caribbean side. This later entry of Pacific taxa into the Caribbean had no apparent effect on the subsequent composition of Caribbean faunas.

In this paper we report a new genus Protentelloides and two new species (Protntelloides primitiva and Protentelloides dalhousiei ) from the upper Oligocene (planktonic foraminiferal Zone P22) in DSDP Hole 366A on the Sierra Leone Rise, eastern equatorial Atlantic. We suggest that Protentelloides is one of the phylogenetic branches of Globorotaloides suteri (Bolli). Protentelloides dalhousiei evolved from P. primitiva. Protentelloides primitiva and Protentelloides dalhousiei are suggested to have a duration of about 1.3 and 0.45 m.y., respectively. These two taxa are considered to be stratigraphically important in determining the upper Oligocene (Zone P22) and the Oligocene/Miocene boundary because of their short stratigraphic ranges and diagnostic features. The last occurrences of the two taxa are juxtaposed at ca. 23.2 Ma, only 0.5 m.y. earlier than the first occurrence of Globorotalia kugleri that has been used recently as the most reliable Oligocene/Miocene boundary marker. Hence, the two species can be suggested as secondary indicators of the O/M boundary. GEOLOGICAL SET'lINGS AND METHODS During Leg 41 of the Deep Sea Drilling Project (DSDP), Hole 366A was drilled at a water depth of 2853m on the Sierra Leone Rise, eastern equatorial Atlantic (05?40.7'N, 19?51.1'W; text-fig. 1) (Lancelot et al. 1978). Hole 366A contains well-preserved Oligocene deposits with perfectly preserved assemblages of planktonic foraminifera (Krasheninnikov and Pflaumann 1978). A detailed study of planktonic foraminiferal biostratigraphy was conducted recently by Miller et al. (1989), and showed continuous sedimentation during the Oligocene, with the exception of a possible hiatus between Zones P21a and P22, suggesting that Zone P21b may be missing (text-fig. 2). The duration of the hiatus has been estimated to be approximately 1.4 m.y. (29.6-28.2 Ma; Miller et al. 1989). The remaining upper Oligocene represented by Zone P22 is approximately 50m, ranging from cores 32 to 28, and is conformably overlain by Zone N4, the base of the lower Miocene. Here we have re-examined this material for planktonic foraminifera and report two new species that we believe to be important stratigraphic markers, and to provide discussion of their stratigraphic ranges and probable phylogenetic lineage. Samples were processed at Lamont-Doherty Earth Observatory, Columbia University, New York, USA. They were soaked in a 3% hydrogen peroxide solution, washed through a 63gm sieve with a sodium metaphosphate solution, and air-dried. SYSTEMATIC DESCRIPTIONS Protentelloides Zhang and Scott, n. gen. Diagnosis: Test free, thick-walled, very low trochospiral in early stage, followed by a tendency to become planispiral in final whorl. Chambers globular in early stages, but molar-shaped in final whorl, increasing rapidly in size as added, greatly inflated at peripheral end, and suddenly flattened in the center of test, with a steep slope half way between the umbilicus and periphery; 4-6 chambers in the final whorl. A bulla-like chamber commonly developed as a final chamber, which varies greatly in shape, from distinct to extremely obscure or absent, more or less equatorially centered. Proloculus and first few initial chambers very small, making the center of test particularly thin. Equatorial periphery lobulate to strongly lobulate, axial periphery broadly rounded. Sutures on both sides simple, almost radial, depressed, straight in early stage; last few intercameral sutures curved to recurved, limbate but depressed, never flush to the test; in some specimens the sutures are not clear in the widely compressed center (see pl. 1, fig. 6). Aperture varies significantly; type species has a large prolonged aperture that is symmetrical in axial view, linking with primary umbilical-extraumbilival basal aperture, forming somewhat "2-ray" aperture as seen in the Eocene genus Hantkenina, with distinctly projected imperforate rim and dendritic tooth that creates secondary openings inside the aperture (see pl. 1, figs. 12c and d); however in most specimens 1-3 secondary prolonged or circular openings are irregularly scattered on the areal face of the bulla-like chamber. In primitive forms, the primary aperture is a slit-like opening or a low arch at the ventral base of the bulla-like or extremely reduced chamber, interiomarginal, umbilical-extraumbilical, with a rim. Surface coarsely perforate, cancellate, hexagonal (pl. 1, fig. ld). Remarks: This genus resembles the genus Protentella (Lipps 1964) in chamber arrangement reported from the Monterey Shale, uppermost Luisian, middle Miocene (planktonic foraminiferal Zones N12-14), Southern California, but differs from it in its large prolonged aperture that is axially symmetrical with distinct rim and dendritic tooth inside the aperture, and bulla-like last chamber with or without secondary areal openings in early forms, molar-shaped chambers, and cancellate surface structure. Type species: Protentelloides dalhousiei Zhang and Scott, n. sp., 1995. Generic derivation: The name Protentelloides was chosen because of the similar chamber arrangement exhibited by Protentella Lipps 1964. The suffix, oides, means "similar". Pro ntelloides primitiva Zhang and Scott, n. sp. Pl te 1, figures 1-3 Description: Test free, very low trochospiral, 7-8 chambers in 1 1/2 whorls on dorsal side. Chambers globular to subglobular, holotype (pl. 1, fig. la-c) shows somewhat molar-shaped chambers in last whorl, increasing rapidly in size as added; 4-6 chambers in the final whorl, the final chamber taking over about 1/4 to 1/3 of the micropaleontology, vol. 41, no. 1, pp. 77-83, text-figures 1-2, plate 1, table 1, 1995 77 This content downloaded from 207.46.13.83 on Fri, 21 Oct 2016 04:35:09 UTC All use subject to http://about.jstor.org/terms Jijun Zhang and David B. Scott: New planktonic foraminiferal genus and species from the upper Oligocene, DSDP Hole 366A, Leg 41 100 900 800 70 ? 600 500 400 300 200 10 0 00 100 n_ _ TEXT-FIGURE 1 Location map showing DSDP Hole 366A (after Miller et al. 1989); the numbers 1, 4 and 5 indicate contours in kilometer and the dot-shadowed areas are the basins greater than 5 km below the present sea level. F.Z. = fracture zone. 78 This content downloaded from 207.46.13.83 on Fri, 21 Oct 2016 04:35:09 UTC All use subject to http://about.jstor.org/terms Micropaleontology, vol. 41, no. 1, 1995

We have evaluated the planktonic foraminiferal biostratigraphy of several Gulf of Mexico Eureka boreholes, emphasizing the Miocene depositional history of the northeastern region (De Soto Canyon). The E68-136 borehole (De Soto Canyon; 1826', 557m present depth) provides the most continuous Miocene record, although deposition was punctuated by several short (

In view of recent controversy over the number and timing of late Eocene impact events, we evaluated biostratigraphic correlations at Deep Sea Drilling Project (DSDP) Site 612, New Jersey continental slope. Radiolarian and foraminiferal biostratigraphy indicate that the tektite layer at Site 612 is biostratigraphically older than a microtektite layer in Barbados which has been correlated with the North American strewn field. Strontium and oxygen isotope stratigraphies are consistent with magnetobiostratigraphic correlations. The late Eocene impact events do not correlate with climate changes inferred from the marine isotope record

Calcareous nannoplankton have been investigated in 22 samples collected from the East China Sea continental shelf and 36 indigenous taxa identified. Nannoplankton abundance and diversity increase progressively in a seaward direction, reflecting changes in water temperature, salinity and terrigenous sediment input to the shelf. The chief environmental factors controlling the distribution of modem nannoplankton assemblages are the cold inshore Coastal Current flowing southward and the warm Kuroshio Current flowing northeastward over the southern middle and outer shelf. The continental shelf can be divided into three zones based on the nannoplankton assemblage: 1) an inner-shelf zone (Gephyrocapsa oceanica Zone) which is low in nannoplankton abundance and diversity and in which the species present are overwhelmingly dominated by G. oceanica; 2) a zone approximating the middle shelf (Gephyrocapsa oceanica-Emiliania huxleyi Zone) in which abundance and diversity are moderate-with G. oceanica and E. huxleyi the dominant species and G. oceanica predominating; and 3) an outer-shelf zone (Emiliania huxleyi-Gephyrocapsa oceanica Zone) of much abundance and diversity, with E. huxleyi predominant over G. oceanica.