Chaim Benjamini
Ben-Gurion University of the Negev
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Featured researches published by Chaim Benjamini.
Geology | 1998
Sigal Abramovich; Ahuva Almogi-Labin; Chaim Benjamini
An outer shelf–upper slope tropical Tethyan pelagic environment existed over southern Israel during Maastrichtian time. Planktic foraminifera in the >63 and >149 µm size fractions from four sections in this area were studied quantitatively for a high-resolution ecostratigraphic analysis of the pre–Cretaceous-Tertiary (K-T) paleoenvironment. During the Maastrichtian, 41% of the planktic foraminifera species became extinct, mostly keeled Globotruncanidae , which also became quantitatively reduced near the end of the Maastrichtian from as much as 35% to only 5% of the planktic foraminifera population. Evolutionary replacement of extinct species by new forms nearly ceased in that interval. Two major opportunistic blooms of Guembelitria took place, associated with reduced abundances of keeled forms and the dominant species Heterohelix globulosa . The first bloom occurred within the upper Gansserina gansseri to lower Abathomphalus mayaroensis Zones and the second within the Plummerita hantkeninoides Zone. The extinctions, concomitant changes in faunal dominance, and opportunist blooms indicate that the pelagic ecosystem in the Negev area experienced multiple stresses during the Maastrichtian. The planktic foraminiferal assemblages were taxonomically impoverished and in decline prior to the K-T boundary crisis.
Marine Micropaleontology | 1992
Y. Eshet; S. Moshkovitz; Daniel Habib; Chaim Benjamini; M. Magaritz
In Israel, the Cretaceous/Tertiary (K/T) boundary at Hor Hahar occurs within the interval from the top of the Ghareb Formation (Maastrichtian) to just below the horizon of dark marl and clay within the overlying Taqiye Formation (Paleocene). The studied interval contains all the calcareous nannofossil zones:Micula prinsii (latest Maastrichtian),Markalius inversus — NP1 (earliest Paleocene), andCruciplacolithus tenuis — NP2 (Early Paleocene). They correlate in sequence with theAbathomphalus mayaroensis, P0 P1a, P1b, and P1c planktic foraminiferal zones. The palynological assemblages consist mainly of dinocysts with only few pollen grains and spores. These assemblages are used to interpret five stratigraphic phases of environmental change across the K/T boundary in the Hor Hahar section. In the latest Maastrichtian, there is an overwhelming dominance of the nannofossilMicula decussata, which probably reflects environmental stress preceding the terminal Cretaceous mass extinction. A nearshore marine environment at the boundary is suggested by the increase in number of specimens of the dinocystCyclonephelium, and by the predominance of terrigenous organic matter sediment. There followed two episodes of transgression and regression. The calcareous cyst-producing dinoflagellateThoracosphaera (Futterer, 1976) becomes dominant in two episodes at the boundary and approximately one meter above it. It alternates in abundance with the organic-walled dinoflagellates, which suggests that different environmental parameters were operating for each group. Maastrichtian dinocysts decline in abundance toward the K/T boundary. They reach greatest abundance and species diversity at the same strata where foraminiferids recover after their mass extinction at the boundary. Calcareous nannofossils recover only later in the early Paleocene. Changes in δ13C and total organic carbon, as as well as dinocyst and nannofossil composition indicate an episode of strong ecological stress about one meter above the boundary.
PALAIOS | 1991
Gerta Keller; Chaim Benjamini
Paleoenvironmental conditions of the early Paleocene eastern Tethys have been inferred based on carbonate sedimentation, biostratigraphy, and planktic foraminiferal assemblages of five sections from the Negev of Israel. In the earliest Paleocene at least three intervals of erosion or nondeposition of sediments have been identified (K/ T, PO/Pla, Pla/Plb boundaries) in addition to a black pyriteand organic-rich clay layer about 1.5 to 3.0 m above the KIT boundary (Subzone Pl b/P1c, upper Chron 29N). These hiatuses appear to be widespread and correlate with global sea level fluctuations. Danian planktic foraminiferal assemblages of the eastern Tethys are dominated by alternating abundance maxima between triserial (Guembelitria) and biserial (Woodringina, Chiloguembelina) species. Biogeographic distribution of these taxa indicates that both groups thrived in shallow continental shelf regions. Moreover, abundance maxima of triserial taxa seem to correspond to 613C depletion intervals, which indicate low surface productivity, whereas abundance maxima of biserial taxa correspond to enriched 613C intervals which imply high surface productivity. These paleoceanographic changes may be related to sea level highand lowstands during the earliest Paleocene. Stable isotope analyses of Danian species will be necessary to confirm these observations and to reconstruct oceanic conditions in both open marine and continental shelf regions of the early Paleocene.
Marine Pollution Bulletin | 2009
Orit Hyams-Kaphzan; Ahuva Almogi-Labin; Chaim Benjamini; Barak Herut
The eastern Mediterranean is naturally highly oligotrophic, but urbanization along the Levant coast has led to raised organic and nutrient loads. This study tracks living foraminiferal assemblages at two sites near an activated sewage sludge outfall from 11/2003 to 5/2004. Oligotrophic site PL29 shows seasonal variations in O(2), chlorophyll a, and organic carbon, and has an abundant, diverse benthic foraminiferal assemblage living at various in-sediment depths. At eutrophic site PL3, approximately 16 years of sludge injection favor a depleted assemblage primarily of opportunist foraminifera. This site shows less seasonality, is subjected to organic matter overload, O(2)-stress, and periodic anoxia, foraminifera are less abundant and diverse, and live at shallower depths. The assemblages at both sites represent a common pool of species, with Ammonia tepida highly dominant. Benthic foraminifera were therefore found to be sensitive to trophic trajectories, respond on sub-seasonal time-scales, and track injection and dispersal of organic loads on the shelf.
PALAIOS | 1996
Valery S. Samoilov; Chaim Benjamini
Berriasian-Maastrichtian dinosaur remains from South Mongolia (Gobi desert) are characterized by both excellent external appearance and good interior, textural and chemical preservation. Bone remains are carbonate-phosphate in composition with the texture of the Haversian canals preserved. Such preservation resulted from dinosaur burial in subaridic or aridic conditions as a result of mudflow action. All dinosaur remains are enriched in some volatile and trace elements (F, S, REE, Y, Sr, U, etc.), but, at the same time, are chemically heterogeneous. Considerable anisotropy is noted in trace element distribution between bones, egg-shell and coprolite. The bones and coprolite have similar carbonatephosphate composition, but differ in trace element composition, with Yand HREE selectively accumulated in the bones. Different skeletal parts (vertebrae, extremities, ribs, skull, pelvis) are also heterogeneous with the maximum of trace element accumulation in the vertebrae. Epigenesis and sedimentation are not responsible for chemical heterogeneity of the dinosaur remains from Mongolia. Their observed composition formed no later than earliest diagenesis, that is, enrichment in trace elements can be attributed to vital processes and the earliest stage of diagenesis when original organic matter was still present in faunal remains. However, the considerable anisotropy in the distribution of some elements between different parts of the dinosaur skeleton cannot be explained completely by the processes of the earliest stage of diagenesis. Accordingly, it is assumed that dinosaur remains preserve some aspects of vital effects and original biochemistry of dinosaur bone tissues. Consistent changes in bone composition are observed during the course of the Late Cretaceous. Maastrichtian remains are characterized by maximum contents of fluorine and some trace elements. These data may be taken to indicate significant environmental changes in South Mongolia during the Late Cretaceous, especially in the Maastrichtian.
Bulletin De La Societe Geologique De France | 2005
Thierry Adatte; Gerta Keller; Doris Stüben; M. Harting; Utz Kramar; Wolfgang Stinnesbeck; Sigal Abramovich; Chaim Benjamini
The late Maastrichtian to early Danian at Mishor Rotem, Israel, was examined based on geochemistry, bulk rock and clay mineralogies, biostratigraphy and lithology. This section contains four red clay layers of suspect impact or volcanic origin interbedded in chalk and marly chalks. PGE anomalies indicate that only the K/T boundary red layer has an Ir dominated PGE anomaly indicative of an impact source. The late Maastrichtian red clays have Pd dominated PGE anomalies which coincide with increased trace elements of terrigenous and volcanogenic origins. Deccan or Syrian-Turkey arc volcanism is the likely source of volcanism in these clay layers. Glauconite, goethite and translucent amber spherules are present in the clay layers, but the Si-rich spherules reported by Rosenfeld et al. [l989] could not be confirmed. The absence of Cheto smectite indicates that no altered impact glass has been present. The red layers represent condensed sedimentation on topographic highs during sea level highstands. In the Negev area, during the late Maastrichtian, the climate ranged from seasonally wet to more arid conditions during zones CF3 and CF2, with more humid wet conditions in the latest Maastrichtian zone CF1 and in the early Danian, probably linked to greenhouse conditions. Planktic foraminifera experienced relatively high stress conditions during this time as indicated by the low species richness and low abundance of globotruncanids. Times of intensified stress are indicated by the disaster opportunist Guembelitria blooms, which can be correlated to central Egypt and also to Indian Ocean localities associated with mantle plume volcanism. Marine plankton thus support the mineralogical and geochemical observations of volcanic influx and reveal the detrimental biotic effects of intense volcanism.
Palaeogeography, Palaeoclimatology, Palaeoecology | 1992
Mordechai Magaritz; Chaim Benjamini; Gerta Keller; Shimon Moshkovitz
Abstract Carbon and oxygen isotope records from carbonate fractions in marls overlying the K/T boundary in southern Israel are used to interpret paleoenvironmental changes and the history of early diagenetic events in the earliest Tertiary. The δ13C record of the whole rock does not significantly depart from the original values and reflects the global productivity drop shortly after the K/T boundary and the subsequent recovery. Fine fraction oxygen isotope values reflect the addition of carbonate cement highly depleted in 18O throughout the profile. The δ18O record demonstrates two main episodes in which contact with fresh water affected the sediments. One is below a short hiatus at planktic foraminiferal subzone transition PO/P1a (Guembelitria cretacea/Parvularugoglobigerina eugubina) and the other at an pyrite- rich clay layer near the top to planktic foraminiferal subzone P1b (‘Globigerina’ taurica). The latter event suggests introduction of sapropelic bottom conditions in the oceanic paleoenvironment.
Journal of Micropalaeontology | 1991
Avraham Honigstein; A. Rosenfeld; Chaim Benjamini
23 species of ostracods and 20 species and species groups of planktonic foraminifera from the 80m thick Qeren Sartabasection, central Jordan Valley, are described and illustrated. The material is determined by planktonic foraminiferal biostratigraphy to belong to the latest Early Eocene (upper part of Zone P9) and the early Middle Eocene (Zone P10). The palaeoecology is representative of a pelagic marine shelf, with periodic events of shallowing and hardground formation.
Archive | 2012
Ahuva Almogi-Labin; Sarit Ashckenazi-Polivoda; Yael Edelman-Furstenberg; Chaim Benjamini
Anoxic conditions prevailed on the Late Cretaceous seafloor beneath a long-term upwelling system situated across the southern Tethys. In Israel, the acme of this system was during the Campanian, when a suite of characteristic lithofacies (organic-rich carbonate, phosphorite, porcelanite, and chert) was broadly distributed over at least a 250 km wide zone encompassing the paleotopography of the Syrian Arc fold belt and beyond. Stressed faunal associations developed all across this belt. While more ventilated horizons supported molluscan assemblages, laminated sediments with oxygenation levels below 0.1 ml O2/l were macroscopically sterile but were found to support rich foraminiferal microfaunas. These faunas, apparently adapted to near anoxia, are dominated by two highly specialized buliminid species, Neobulimina canadensis and Praebulimina prolixa, in five assemblages that define different levels of oxygen stress. The foraminifera presumably lived below the sediment surface in the pore-water microenvironment, where habitat partitioning depended on food and oxygen resources rather than the nature of the sediment particles. They therefore do not correlate to the sediment type or lithofacies from which they were recovered.
Journal of Micropalaeontology | 1986
Chaim Benjamini; Alexander Chepstow-Lusty
63 conodont elements, referred to four multielement genera (Neospathodus, Cypridodella, Ketinella and Ellisonia) were recovered from the Upper Anisian-Lower Ladinian ‘fossiliferous limestone’ member of the Saharonim Formation, Makhtesh Ramon, Israel. The new form-species Neospathodus shagami sp. nov. is here described. Together with associated conodont elements, this species appears to show a close relationship to more advanced Gondolellaceans. Absence of true platform conodonts in the studied fauna may be due to paleoecological or phylogenetic factors.