Aubry Marie-Pierre

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  • Preprint
    Genesis and geometry of tilted blocks in the Theban Hills, near Luxor (Upper Egypt)
    ( 2011-02-16) Dupuis, Christian ; Aubry, Marie-Pierre ; King, Christopher ; Knox, Robert W. O'B. ; Berggren, William A. ; Youssef, Moustafa ; Galal, Wael Fathi ; Roche, Marc
    The desertic Theban hills between the edge of the alluvial plain of the Nile and the prominent cliffs at the eastern edge of the Theban Plateau consist of imbricated tilted blocks organized in parallel groups representing successive generations of gravitational collapse structures (or slumps). The older (distal) generations correspond to low, rounded hills farther from the Theban cliffs. The youngest (proximal) generation forms higher hills with young relief. Reverse faults occur at the contact between proximal and distal tilted blocks whereas the proximal tilted blocks rest along listric faults on the substratum (Tarawan Chalk and Esna Shale Formations) and against the Theban cliffs. We hypothesize that the emplacements of the tilted blocks were related to major Pleistocene pluvial episodes, each marked by active flow of the Nile River and significant recess of the Theban cliffs. Tectonic thinning and intensive erosion of the Esna Shale Formation were determinant in shaping the Theban landscape.
  • Article
    Subseries/Subepochs approved as a formal rank in the international stratigraphic guide
    (International Union of Geological Sciences, 2020-07-01) Aubry, Marie-Pierre ; Head, Martin J. ; Piller, Werner E. ; Berggren, William A.
    The International Subcommission on Stratigraphic Classification, as the constituent body of the International Commission on Stratigraphy (ICS) responsible for the International Stratigraphic Guide, has voted to include the subseries/ subepoch as a formal rank in the next edition of the Guide. This acknowledges the recent ratification of formal subseries and their corresponding stages for the Holocene Series/Epoch but allows individual subcommissions within ICS the freedom to decide whether or not to adopt this rank for their particular stratigraphic/time interval.
  • Article
    Formation of the Isthmus of Panama
    (American Association for the Advancement of Science, 2016-08-17) O’Dea, Aaron ; Lessios, Harilaos ; Coates, Anthony ; Eytan, Ron I. ; Restrepo-Moreno, Sergio A. ; Cione, Alberto L. ; Collins, Laurel S. ; de Queiroz, Alan ; Farris, David W. ; Norris, Richard D. ; Stallard, Robert ; Woodburne, Michael ; Aguilera, Orangel ; Aubry, Marie-Pierre ; Berggren, William A. ; Budd, Ann F. ; Cozzuol, Mario A. ; Coppard, Simon E. ; Duque-Caro, Hermann ; Finnegan, Seth ; Gasparini, Germán M. ; Grossman, Ethan L. ; Johnson, Kenneth G. ; Keigwin, Lloyd D. ; Knowlton, Nancy ; Leigh, Egbert G. ; Leonard-Pingel, Jill S. ; Marko, Peter B. ; Pyenson, Nicholas ; Rachello-Dolmen, Paola G. ; Soibelzon, Esteban ; Soibelzon, Leopoldo ; Todd, Jonathan A. ; Vermeij, Geerat J. ; Jackson, Jeremy B. C.
    The formation of the Isthmus of Panama stands as one of the greatest natural events of the Cenozoic, driving profound biotic transformations on land and in the oceans. Some recent studies suggest that the Isthmus formed many millions of years earlier than the widely recognized age of approximately 3 million years ago (Ma), a result that if true would revolutionize our understanding of environmental, ecological, and evolutionary change across the Americas. To bring clarity to the question of when the Isthmus of Panama formed, we provide an exhaustive review and reanalysis of geological, paleontological, and molecular records. These independent lines of evidence converge upon a cohesive narrative of gradually emerging land and constricting seaways, with formation of the Isthmus of Panama sensu stricto around 2.8 Ma. The evidence used to support an older isthmus is inconclusive, and we caution against the uncritical acceptance of an isthmus before the Pliocene.
  • Article
    The Dababiya corehole, Upper Nile Valley, Egypt : preliminary results
    (Austrian Geological Society, 2012) Berggren, William A. ; Alegret, Laia ; Aubry, Marie-Pierre ; Cramer, Ben S. ; Dupuis, Christian ; Goolaerts, Sijn ; Kent, Dennis V. ; King, Christopher ; Knox, Robert W. O'B. ; Obaidalla, Nageh ; Ortiz, Silvia ; Ouda, Khaled A. K. ; Abdel-Sabour, Ayman ; Salem, Rehab ; Senosy, Mahmoud M. ; Soliman, Mamdouh F. ; Soliman, Ali
    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.
  • Preprint
    A sea of Lilliputians
    ( 2008-05-27) Aubry, Marie-Pierre
    Smaller size is generally seen as a negative response of organisms to stressful environmental conditions, associated with low diversity and species dominance. The mean size of the coccolithophorids decreased through the Neogene, leading to the prediction that their extant representatives are characterized by poor diversification and low specialization. The study of the (exo)coccospheres of selected taxa in the order Syracosphaerales negates this prediction, revealing that on the contrary some extant lineages are highly diversified and remarkably specialized. Whereas the general role of coccoliths remains indeterminate, this analysis suggests that some highly derived coccoliths may be modified for the collection of food particles, including picoplankton, thus implying that mixotrophy may characterize these lineages. In the extant coccolithophorids, species richness of genera is inversely correlated with the size of cells, definitive evidence that small size is part of a morphologic strategy rather than a sign of evolutionary failure. Because of their extreme minuteness, the extant nannoplankton can be well compared to Lilliputians, but the trend toward size decrease in Neogene lineages is not attributable to the Lilliput effect described by Urbanek (1993).
  • Preprint
    Anatomy of a mountain : the Thebes Limestone Formation (Lower Eocene) at Gebel Gurnah, Luxor, Nile Valley, Upper Egypt
    ( 2017-05) King, Christopher ; Dupuis, Christian ; Aubry, Marie-Pierre ; Berggren, William A. ; Knox, Robert W. O'B. ; Galal, Wael Fathi ; Baele, Jean-Marc
    We present a detailed geologic study of the Thebes Formation at Gebel Gurnah in its locus typicus on the West Bank (opposite Luxor) of the Nile River in the Upper Nile Valley, Egypt. This is the first detailed measurement and lithologic description of the ~ 340 m thick (predominantly) carbonate section. The Thebes Formation is divided into thirteen major lithic units (A to M). We interpret data on the lithologic succession and variations, whole rock/clay mineralogy, and macro/micropaleontology in terms of deposition on a shallow carbonate platform episodically influenced by continental runoff, and describe six depositional sequences that we place in the global framework of Lower Eocene (Ypresian) sequence stratigraphy. We note however significant incompatibilities between the Thebes depositional sequences and the global sequences. We emend the definition of the Thebes Formation by defining its top as corresponding to level 326 m at the top of Nodular Limestone ‘L’ (NLL), and assigning the overlying beds to the Minia Limestone Formation. New biostratigraphic data and revision of previous studies establish the direct assignment of the Thebes Formation to planktonic foraminiferal Zones E4/P6b (upper part), E5/P7 and (indirectly) Zone E6/P8, and (probably, indirectly) Zone E7a/”P9”, and to calcareous nannofossil Zone NP12 and lower Zone NP13 of the Lower Eocene (Ypresian) and provide a temporal framework spanning ~ 2.8 Myr from <52.45 to ~49.6 Ma for the deposition of the Thebes Formation prior to the prominent sea level fall (~ 49.6 Ma) towards the end of the Early Eocene. Dominantly carbonate deposition, with a strongly reduced detrital influx, occurred on a very wide shelf (probably) at least ~ 100 km from the coastline. The thick sedimentary succession and the marked vertical lithologic variations are interpreted as resulting from sea level fluctuations imprinted on a long-term decrease in sea-level associated with rapid subsidence reflecting tectonic relaxation after the major Late Paleocene tectonic reorganization of the Syrian Arc.
  • Preprint
    Pharaonic necrostratigraphy : a review of geological and archaeological studies in the Theban Necropolis, Luxor, West Bank, Egypt
    ( 2008-11-09) Aubry, Marie-Pierre ; Berggren, William A. ; Dupuis, Christian ; Ghaly, Holeil ; Ward, David ; King, Christopher ; Knox, Robert W. O'B. ; Ouda, Khaled A. K. ; Youssef, Moustafa ; Galal, Wael Fathi
    We present a review of archeological and geological studies on the West Bank as a basis for discussing the geological setting of the tombs and geologically related problems with a view to providing archeologists with a framework in which to conduct their investigations on the restoration, preservation and management of the antique monuments. Whereas the geology of the Upper Nile Valley appears to be deceptively simple, the lithologic succession is vertically variable, and we have recognized and defined several new lithologic units within the upper Esna Shale Formation. We have been able to delineate lithologic (shale/limestone) contacts in several tombs and observed that the main chambers in some were excavated below the Esna Shale in the Tarawan Chalk Formation. We have been able to document changing dip in the strata (warping) in several tombs, and to delineate two major orientations of fractures in the field. Investigations behind the Temple of Hatshepsut, in the Valley of the Kings and around Deir El Medina, have revealed four broad regional structures. We confirm that the hills located near the Nile Valley, such as Sheik Abel Qurna, do not belong to the tabular structure of the Theban Mountain, but are discrete displaced blocks of the Thebes Limestone and overlying El Miniya, as supported by Google Earth photographs.
  • Article
    The Neogene and Quaternary : chronostratigraphic compromise or non-overlapping magisteria?
    (Micropaleontology Press, 2009-03) Aubry, Marie-Pierre ; Berggren, William A. ; Van Couvering, John ; McGowran, Brian ; Hilgen, Frits ; Steininger, Fritz ; Lourens, Lucas
    The International Commission on Stratigraphy (ICS) together with its subcommissions on Neogene Stratigraphy (SNS) and Quaternary Stratigraphy (SQS) are facing a persistent conundrum regarding the status of the Quaternary, and the implications for the Neogene System/Period and the Pleistocene Series/Epoch. The SQS, in seeking a formal role for the Quaternary in the standard time scale, has put forward reasons not only to truncate and redefine the Neogene in order to accommodate this unit as a third System/Period in the Cenozoic, but furthermore to shift the base of the Pleistocene to c. 2.6 Ma to conform to a new appreciation of when “Quaternary climates” began. The present authors, as members of SNS, support the well-established concept of a Neogene extending to the Recent, as well as the integrity of the Pleistocene according to its classical meaning, and have published arguments for workable options that avoid this conflict. In this paper, we return to the basic principles involved in the conversion of the essentially marine biostratigraphic/ biochronologic units of Lyell and other 19th-century stratigraphers into the modern hierarchical arrangement of chronostratigraphic units, embodied in the Global Standard Stratotype-section and Point (GSSP) formulation for boundary definitions. Seen in this light, an immediate problem arises from the fact that the Quaternary, either in its original sense as a state of consolidation or in the more common sense as a paleoclimatic entity, is conceptually different from a Lyellian unit, and that a Neogene/Quaternary boundary may therefore be a non sequitur. Secondly, as to retaining the base of the Pleistocene at 1.8 Ma, the basic hierarchical principles dictate that changing the boundary of any non-fundamental or “higher” chronostratigraphic unit is not possible without moving the boundary of its constituent fundamental unit. Therefore, to move the base of the Pleistocene, which is presently defined by the Calabrian GSSP at 1.8 Ma, to be identified with the Gelasian GSSP at 2.6 Ma, requires action to formally redefine the Gelasian as part of the Pleistocene. Finally, it is important to keep in mind that the subject under discussion is chronostratigraphy, not biostratigraphy. Both systems are based on the fossil record, but biostratigraphic units are created to subdivide and correlate stratigraphic sequences. The higher-level units of chronostratigraphy, however, were initially selected to reflect the history of life through geological time. The persistence of a characteristic biota in the face of environmental pressures during the last 23 my argues strongly for the concept of an undivided Neogene that extends to the present. Several ways to accommodate the Quaternary in the standard time scale can be envisaged that preserve the original concepts of the Neogene and Pleistocene. The option presently recommended by SNS, and most compatible with the SQS position, is to denominate the Quaternary as a subperiod/subsystem of the Neogene, decoupled from the Pleistocene so that its base can be identified with the Gelasian GSSP at c. 2.6 Ma. A second option is to retain strict hierarchy by restricting a Quaternary subperiod to the limits of the Pleistocene at 1.8 Ma. As a third option, the Quaternary could be a subera/suberathem or a supersystem/ superperiod, decoupled from the Neogene and thus with its base free to coincide with a convenient marker such as the base of the Pleistocene at 1.8 Ma, or to the Gelasian at 2.6 Ma, as opinions about paleoclimatology dictate. If no compromise can be reached within hierarchical chronostratigraphy, however, an alternative might be to consider Quaternary and Neogene as mutually exclusive categories (climatostratigraphic vs. chronostratigraphic) in historical geology. In this case, we would recommend the application of the principle of NOMA, or Non-Overlapping Magisteria, in the sense of the elegant essay by the late Stephen J. Gould (1999) on the mutually exclusive categories of Religion and Science. In this case the Quaternary would have its own independent status as a climatostratigraphic unit with its own subdivisions based on climatic criteria.