Publication Date:
2022-05-25
Description:
Author Posting. © Austrian Geological Society, 2012. This article is posted here by permission of Austrian Geological Society for personal use, not for redistribution. The definitive version was published in Austrian Journal of Earth Sciences 105, no. 1 (2012): 161-168.
Description:
The Dababiya corehole was drilled in the Dababiya Quarry (Upper Nile Valley, Egypt), adjacent to the GSSP for the Paleocene/
Eocene boundary, to a total depth of 140 m and bottomed in the lower Maastrichtian Globotruncana aegyptiaca Zone of the Dakhla
Shale Formation. Preliminary integrated studies on calcareous plankton (foraminifera, nannoplankton), benthic foraminifera, dinoflagellates,
ammonites, geochemistry, clay mineralogy and geophysical logging indicate that: 1) The K/P boundary lies between
80.4 and 80.2 m, the Danian/Selandian boundary between ~ 41 and 43 m, the Selandian/Thanetian boundary at ~ 30 m (within the
mid-part of the Tarawan Chalk) and the Paleocene/Eocene boundary at 11.75 m (base [planktonic foraminifera] Zone E1 and [calcareous
nannoplankton] Zone NP9b); 2) the Dababiya Quarry Member (=Paleocene/Eocene Thermal Maximum interval) extends
from 11.75 to 9.5 m, which is ~1 m less than in the adjacent GSSP outcrop.; 3) the Late Cretaceous (Maastrichtian) depositional
environment was nearshore, tropical-sub tropical and nutrient rich; the latest Maastrichtian somewhat more restricted (coastal); and
the early Danian cooler, low(er) salinity with increasing warmth and depth of water (i.e., more open water); 4) the Paleocene is further
characterized by outer shelf (~ 200 m), warm water environments as supported by foraminifera P/B ratios 〉 85% (~79-28 m),
whereas benthic foraminifera dominate (〉70%) from ~27-12 m (Tarawan Chalk and Hanadi Member) due, perhaps, in part to increased
dissolution (as observed in nearby outcrop samples over this interval); 5) during the PETM, enhanced hydrodynamic conditions
are inferred to have occurred on the sea-floor with increased river discharge (in agreement with sedimentologic evidence),
itself a likely cause for very high enhanced biological productivity on the epicontinental shelf of Egypt; 6) correlation of in situ measured
geophysical logs of Natural Gamma Ray (GR), Single-Point Resistance (PR), Self-Potential (SP), magnetic susceptibility
(MS), and Resistivity, and Short Normal (SN) and Long Normal (LN) showed correspondence to the lithologic units. The Dababiya
Quarry Member, in particular, is characterized by very high Gamma Ray and Resistivity Short Normal values.
Description:
The Dababiya corehole was made possible by the
financial support of the National Geographic Society.
Keywords:
Dakhla and Esna Shale Formations
;
Upper Cretaceous and Paleocene
;
Dababiya Quarry
;
Tarawan Chalk
;
Stratigraphy
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
application/pdf
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