Stable isotope (δ<sup>13</sup>C, δ<sup>18</sup>O) records across the paleocene section at Gebel Oweina, Egypt

Charisi, Stella D.; Schmitz, Birger

doi:10.1080/11035899409546147

Cited by 3 publications

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“…This tectonic and eustatic event may have been responsible for the shift in the locus of ongoing deepwater formation from cold and nutrient-depleted deep waters produced in the polar (Artic and Antarctic) region to warm, saline, and oxygen-deficient deep waters formed in Tethyan evaporative basins (Miller et al 1987;Stott 1990, 1991;Thomas 1990;Katz and Miller 1991;Pak and Miller 1992;Charisi and Schmitz 1994Lu et al 1996). Therefore, the P/E boundary event is usually explained by quick incursions of warm, saline, and nutrient-depleted water masses towards the poles that triggered the high-latitude warming (Rea et al 1990).…”

Section: Discussionmentioning

confidence: 99%

Planktic foraminiferal and 13 C isotopic changes across the Paleocene/Eocene boundary at Possagno (Italy)

Arenillas¹,

Molina²,

Schmitz

1999

International Journal of Earth Sciences

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The interval spanning the Paleocene-Eocene (P/E) transition in the Possagno section consists of 1 m of red marls, including a 4-cm-thick, dark-red "dissolution" clay, which represents the Paleocene/Eocene boundary event. The Possagno section is much more condensed than other Tethyan and North Atlantic sections previously studied; however, in this section the most significant biotic, isotopic and sedimentological events across the P/E boundary can be recognized. The Possagno section spans the following planktic foraminiferal subzones: upper part of M. gracilis Subzone, A. berggreni Subzone, A. sibaiyaensis Subzone and probably lowermost part of P. wilcoxensis Subzone. The quantitative analysis indicates a major increase of lowlatitude acarininids, including compressed tropical acarininids just above the boundary clay. This acarininid incursion begins just below the boundary clay but reaches its maximum just above the clay. The planktic foraminiferal faunal turnover is gradual except for the acarininid incursion. The isotopic results show a negative excursion in i 13 C values at the small benthic foraminifera mass extinction event. The acarininid maximum diversity coincides with this isotopic excursion, and reflects an increase in surface seawater temperature. Despite being very condensed, the Possagno section allows us to further confirm that the different biotic, isotopic and sedimentological events recognized in the Spanish sections (Alamedilla, Campo, Caravaca, Zumaya) are not local in nature and allows the establishment of a detailed chronostratigraphic framework to define the P/E boundary stratotype.

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Section: Discussionmentioning

confidence: 99%

Planktic foraminiferal and 13 C isotopic changes across the Paleocene/Eocene boundary at Possagno (Italy)

Arenillas¹,

Molina²,

Schmitz

1999

International Journal of Earth Sciences

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The impact of Paleocene/Eocene boundary events on middle neritic benthic foraminiferal assemblages from Egypt

Speijer

Zwaan

Schmitz

1996

Marine Micropaleontology

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A 25 m upper Paleocene to lower Eocene marly sequence exposed at Gebel Duwi, (Quseir, Red Sea coast of Egypt) provides a good opportunity for studying Paleocene/Eocene (P/E) boundary stratigraphy and events. Various bio-, eco-, and isotope stratigraphic correlations accurately delineate the position of the P/E boundary (i.e. the level of stable isotopic excursions and deep-sea benthic extinctions) in the middle part of this section, within Zones P5 and NP9. In this paper the impact of P/E boundary environmental perturbations on benthic foraminiferal communities of the shallow Tethyan shelf is examined.Benthic foraminiferal assemblages from Gebel Duwi, characterized by large Frondicularia phosphatica and F. nakkadyi in addition to a number of other neritic taxa, but without any typical outer neritic-bathyal taxa, suggest middle neritic (75-100 m) deposition throughout the studied interval and only minor relative sea-level variations (perhaps some 10-20 m). Across the boundary sea-level appears to have been stable. Yet, a distinct fauna1 turnover marks the P/E boundary of this shallow site, which, in contrast to deep-sea records, is less abrupt, being preceded by a gradual diversity decrease starting some four meters below the boundary. Moreover, most exits are either local or just temporary and thus not true extinctions: many (Lazarus) taxa reappear at some point above the boundary, while all but one of the disappearing taxa are known from other lower Eocene neritic deposits in Egypt.In general, benthic foraminiferal assemblages display low diversities and high dominance values (notably Anomalinoides aegyptiacus: up to 74%), suggesting high levels of environmental stress at the sea-floor. In combination with occasionally very high P/B ratio's (up to 98%P), and generally laminated sediments, the character of the benthic assemblage points to a strong influence of recurrent dysoxia and/or anoxia. We suggest that these resulted from surface eutrophication by (intermittent) coastal upwelling and reduced ventilation of the bottom environment. Although these conditions prevailed during most of the time-interval studied, they were most severe during the latest Paleocene and early Eocene when eutrophication intensified, and the organic carbon flux to the sea-floor increased. Enhanced atmospheric contrasts between the Tethys seaway and the African continent, resulting in intensified longshore tradewinds, may have controlled these changes.At the P/E boundary the bottom environment became minimally ventilated, perhaps due to reduced oxygen advection from deeper waters. Three meters above the boundary a succession of increasingly diverse assemblages indicate a gradual

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Paleocene sea‐level fluctuations recorded in benthic foraminiferal assemblages from gebel oweina (Esna, Egypt): Local, regional or global patterns?

Speijer

1994

GFF

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Stratotype Points (GSP) is that they represent reference points where both geological time and rock are defined. Traditionally, geological history has been perceived in two ways, one rock-related and one time-related. This is manifested in the conventional twosplit stratigraphic (time) scale where chronostratigraphical units (system, series, stage) are matched against geochronological units (period, epoch, age). One principal reason why this divided perception originally evolved, were the uncertainties in correlation that arouse because (immaterial) time boundaries were not satisfactorily defined in relation to (material) rock boundaries. The GSP represents the base of a rock unit as well as the beginning of a time unit, which both continue up to the next asp, and the conventional, divided perception of Earth history will be oflimited practical value after GSSP-standardization (at least in global stratigraphic studies; in regional studies, however, it may still be important to distinguish between time and rock units). Harland et al. (1989) states that, with time and rock deriving from the same standard reference point, "the two apparent! y distinct disciplines geochronology and chronostratigraphy will be different aspects of a single procedure". These authors suggest that the terms period, epoch, and stage shall be used for the different hier- Meeting proceedings "Stratigraphy of the Paleocene" 63archies of time-rock subunits in a GSSP-standardized scale. The terms period and epoch, they adopt from the traditional~eochrono-logic scale, but for the next lower-in-rank time-rock unit, the geochronologic concept "age" is abandoned in favor of the chronostratigraphic concept "stage". The term "age" is dismissed in order to avoid ambiguity because of its general reference to time. However, if traditional geochronologic nomenc1ature, and including also the tenn "age", was used for the GSP-bounded time-rock subunits, the concept "Selandian Age" would refer to such a unit, whereas "Selandian Stage" could be used in a chronostratigraphic sense with reference to the historical stratotype sections. The double meaning of "age" is a minor problem (cf. "period" and "epoch" that refer also to time intervals in general) compared with introducing two stratjgraphic meanings of the term "stage".

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Stable isotope (δ¹³C, δ¹⁸O) records across the paleocene section at Gebel Oweina, Egypt

Cited by 3 publications

References 4 publications

Planktic foraminiferal and 13 C isotopic changes across the Paleocene/Eocene boundary at Possagno (Italy)

Planktic foraminiferal and 13 C isotopic changes across the Paleocene/Eocene boundary at Possagno (Italy)

The impact of Paleocene/Eocene boundary events on middle neritic benthic foraminiferal assemblages from Egypt

Paleocene sea‐level fluctuations recorded in benthic foraminiferal assemblages from gebel oweina (Esna, Egypt): Local, regional or global patterns?

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Stable isotope (δ13C, δ18O) records across the paleocene section at Gebel Oweina, Egypt

Cited by 3 publications

References 4 publications

Planktic foraminiferal and 13 C isotopic changes across the Paleocene/Eocene boundary at Possagno (Italy)

Planktic foraminiferal and 13 C isotopic changes across the Paleocene/Eocene boundary at Possagno (Italy)

The impact of Paleocene/Eocene boundary events on middle neritic benthic foraminiferal assemblages from Egypt

Paleocene sea‐level fluctuations recorded in benthic foraminiferal assemblages from gebel oweina (Esna, Egypt): Local, regional or global patterns?

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Stable isotope (δ¹³C, δ¹⁸O) records across the paleocene section at Gebel Oweina, Egypt