Facies analysis and palaeoclimatic significance of ironstones formed during the Eocene greenhouse

Lower and middle Eocene ironstone sequences of the Naqb and Qazzun formations from the north-east Bahariya Depression, Western Desert, Egypt, represent a proxy for early Palaeogene climate and sea-level changes. These sequences represent the only Palaeogene economic ooidal ironstone record of the Southern Tethys. These ironstone sequences rest unconformably on three structurally controlled Cenomanian palaeohighs (for example, the Gedida, Harra and Ghorabi mines) and formed on the inner ramp of a carbonate platform. These palaeohighs were exposed and subjected to subaerial lateritic weathering from the Cenomanian to early Eocene. The lower and middle Eocene ironstone sequences consist of quiet water ironstone facies overlain by higher energy ironstone facies. The distribution of low-energy ironstone facies is controlled by depositional relief. These deposits consist of lagoonal, burrow-mottled mud-ironstone and laterally equivalent tidal flat, stromatolitic ironstones. The agitated water ironstone facies consist of shallow subtidal–intertidal nummulitic–ooidal–oncoidal and back-barrier storm-generated fossiliferous ironstones. The formation of these marginal marine sequences was associated with major marine transgressive–regressive megacycles that separated by subaerial exposure and lateritic weathering. The formation of lateritic palaeosols with their characteristic dissolution and reprecipitation features, such as colloform texture and alveolar voids, implies periods of humid and warm climate followed major marine regressions. The formation of the lower to middle Eocene ironstone succession and the associated lateritic palaeosols can be linked to the early Palaeogene global warming and eustatic sea-level changes. The reworking of the middle Eocene palaeosol and the deposition of the upper Eocene phosphate-rich glauconitic sandstones of the overlying Hamra Formation may record the initial stages of the palaeoclimatic transition from greenhouse to icehouse conditions.

[1]  A. Hallam,et al.  Bituminous shales and oolitic ironstones as indicators of transgressions and regressions , 1979, Journal of the Geological Society.

[2]  Fabio Florindo,et al.  Coupled Greenhouse Warming and Deep Sea Acidification in the Middle Eocene , 2009 .

[3]  A. Lotter,et al.  Eustatic variations during the Paleocene‐Eocene greenhouse world , 2008 .

[4]  G. Dickens.  Carbon cycle: The blast in the past , 1999, Nature.

[5]  S. Roberts,et al.  Climate change and the formation of nickel laterite deposits , 2012 .

[6]  J. B. Maynard,et al.  Geochemistry of oolitic iron ores, an electron microprobe study , 1986 .

[7]  Caroline H. Lear,et al.  Rapid stepwise onset of Antarctic glaciation and deeper calcite compensation in the Pacific Ocean , 2005, Nature.

[8]  P. Collin,et al.  Depositional environments and iron ooid formation in condensed sections (Callovian–Oxfordian, south‐eastern Paris basin, France) , 2005 .

[9]  M. Purucker,et al.  Glauconitic peloids and chamositic ooids - favorable factors, constraints, and problems , 1984 .

[10]  R. Speijer,et al.  Ostracode turnover and sea-level changes associated with the Paleocene-Eocene thermal maximum , 2002 .

[11]  Gerald R. Dickens,et al.  An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics , 2008, Nature.

[12]  C. Ridder,et al.  Iron Bacterial and fungal mats, Bajocian stratotype (Mid-Jurassic, northern Normandy, France) , 2000 .

[13]  R. Gawthorpe,et al.  Carbonate Cementation in a Sequence-Stratigraphic Framework: Upper Cretaceous Sandstones, Book Cliffs, Utah-Colorado , 2000 .

[14]  U. Sturesson.  Lower Palaeozoic iron oolites and volcanism from a Baltoscandian perspective , 2003 .

[15]  A. Gehring.  The formation of goethitic ooids in condensed Jurassic deposits in northern Switzerland , 1989, Geological Society, London, Special Publications.

[16]  J. Kennett,et al.  Antarctic subtropical humid episode at the Paleocene-Eocene boundary: Clay-mineral evidence , 1994 .

[17]  T. Young.  Eustatically controlled ooidal ironstone deposition: facies relationships of the Ordovician open-shelf ironstones of Western Europe , 1989, Geological Society, London, Special Publications.

[18]  P. Gingerich,et al.  Mammalian generic diversity and turnover in the late Paleocene and early Eocene of the Bighorn and Crazy Mountains Basins, Wyoming and Montana (USA) , 1995 .

[19]  W. Berggren,et al.  The Gebel Owaina and Kilabiya sections in the Idfu-Esna area, Upper Nile Valley (Egypt) , 2003 .

[20]  M. Buxton,et al.  Short Paper: A standardized model for Tethyan Tertiary carbonate ramps , 1989, Journal of the Geological Society.

[21]  U. Sturesson,et al.  Modern and Palaeozoic iron ooids—a similar volcanic origin , 2000 .

[22]  Rushdi Said.  The Geology Of Egypt , 1962 .

[23]  T. Teyssen.  A depositional model for the Liassic Minette ironstones (Luxemburg and France), in comparison with other Phanerozoic oolitic ironstones , 1989, Geological Society, London, Special Publications.

[24]  A. Siehl,et al.  Minette-type ironstones , 1989, Geological Society, London, Special Publications.

[25]  G. Ruffet,et al.  Chemical and physical erosion rhythms of the West African Cenozoic morphogenesis: The 39 Ar- 40 Ar dating of supergene K-Mn oxides , 2008 .

[26]  C. Scheibner,et al.  Late Paleocene early Eocene Tethyan carbonate platform evolution — A response to long- and short-term paleoclimatic change , 2008 .

[27]  W. Krumbein,et al.  Structural diversity of biogenic carbonate particles in microbial mats , 1994 .

[28]  D. Greenwood,et al.  Eocene continental climates and latitudinal temperature gradients , 1995 .

[29]  C. Scheibner,et al.  Turnover of larger foraminifera during the Paleocene-Eocene Thermal Maximum and paleoclimatic control on the evolution of platform ecosystems , 2005 .

[30]  B. Schmitz,et al.  BENTHIC FORAMINIFERAL EXTINCTION AND REPOPULATION IN RESPONSE TO LATEST PALEOCENE TETHYAN ANOXIA , 1997 .

[31]  V. Ciobotă,et al.  Identification of minerals and organic materials in Middle Eocene ironstones from the Bahariya Depression in the Western Desert of Egypt by means of micro‐Raman spectroscopy , 2012 .

[32]  C. Sheppard,et al.  Predicted recurrences of mass coral mortality in the Indian Ocean , 2003, Nature.

[33]  P. Pearson,et al.  Stable warm tropical climate through the Eocene Epoch , 2007 .

[34]  L. Sloan,et al.  Trends, Rhythms, and Aberrations in Global Climate 65 Ma to Present , 2001, Science.

[35]  D. Kelly,et al.  Response of Antarctic (ODP Site 690) planktonic foraminifera to the Paleocene–Eocene thermal maximum: Faunal evidence for ocean/climate change , 2002 .

[36]  G. Retallack.  Lateritization and Bauxitization Events , 2010 .

[37]  M. Chan.  Oolitic Ironstone of the Cretaceous Western Interior Seaway, East-Central Utah , 1992 .

[38]  J. Macquaker,et al.  Sedimentological and geochemical controls on ooidal ironstone and ‘bone-bed’ formation and some comments on their sequence-stratigraphical significance , 1996, Geological Society, London, Special Publications.

[39]  E. Bellosi,et al.  Lateritized tephric palaeosols from Central Patagonia, Argentina: a southern high‐latitude archive of Palaeogene global greenhouse conditions , 2010 .

[40]  J. Chauvel,et al.  Oolitization processes in Palaeozoic ironstones of France, Algeria and Libya , 1989, Geological Society, London, Special Publications.

[41]  B. Schmitz,et al.  Global dinoflagellate event associated with the late Paleocene thermal maximum , 2001 .

[42]  A. Dabous.  Uranium isotopic evidence for the origin of the Bahariya iron deposits, Egypt , 2002 .

[43]  K. Taylor,et al.  Stability and facies association of early diagenetic mineral assemblages; an example from a Jurassic ironstone-mudstone succession, U.K. , 1995 .

[44]  J. Zachos,et al.  Abrupt Climate Change and Transient Climates during the Paleogene: A Marine Perspective , 1993, The Journal of Geology.

[45]  A. Saoudi,et al.  Structural setting and tectonic evolution of the Bahariya Depression, Western Desert, Egypt , 2003, GeoArabia.

[46]  E. El-Hinnawi.  Contributions to the study of Egyptian (UAR) iron ores , 1965 .

[47]  T. Adatte,et al.  Palaeocene- early Eocene climatic evolution in the Tethyan realm: clay mineral evidence , 2001, Clay Minerals.

[48]  C. R. Hughes.  The application of analytical transmission electron microscopy to the study of oolitic ironstones: a preliminary study , 1989, Geological Society, London, Special Publications.

[49]  J. Wagoner.  Sequence Stratigraphy and Marine to Nonmarine Facies Architecture of Foreland Basin Strata, Book Cliffs, Utah, U.S.A. , 1995 .

[50]  R. Gaupp,et al.  Mineral evolution and processes of ferruginous microbialite accretion – an example from the Middle Eocene stromatolitic and ooidal ironstones of the Bahariya Depression, Western Desert, Egypt , 2013, Geobiology.

[51]  W. Kiessling.  Secular Variations in the Phanerozoic Reef Ecosystem , 2002 .

[52]  U. Sturesson,et al.  Lower Ordovician iron ooids and associated oolitic clays in Russia and Estonia: a clue to the origin of iron oolites? , 1999 .

[53]  E. Z. Basta,et al.  El-Gidida iron ores and their origin, Bahariya oases, Western Desert, U.A.R , 1969 .

[54]  J. Heikoop,et al.  Modern iron ooids from a shallow-marine volcanic setting: Mahengetang, Indonesia , 1996 .

[55]  N. Shackleton.  Paleogene stable isotope events , 1986 .

[56]  U. Bayer.  Stratigraphic and environmental patterns of ironstone deposits , 1989, Geological Society, London, Special Publications.

[57]  Michael W. Wara,et al.  A Transient Rise in Tropical Sea Surface Temperature During the Paleocene-Eocene Thermal Maximum , 2003, Science.

[58]  R. Gaupp,et al.  Mineralogical and geochemical investigations of the Middle Eocene ironstones, El Bahariya Depression, Western Desert, Egypt , 2012 .

[59]  D. Schrag,et al.  Beyond methane: Towards a theory for the Paleocene-Eocene Thermal Maximum , 2006 .

[60]  Reto M. Burkhalter.  Ooidal ironstones and ferruginous microbialites: origin and relation to sequence stratigraphy (Aalenian and Bajocian, Swiss Jura mountains) , 1995 .

[61]  J. Serra-Kiel,et al.  Larger Foraminiferal Biostratigraphy of the Tethyan Paleocene and Eocene , 1998 .

[62]  Nageh A. Obaidalla.  Planktonic foraminiferal biostratigraphy and faunal turnover events during the Late Cretaceous-Early Tertiary along the Red Sea Coast, Egypt , 2000 .

[63]  F. B. Houten,et al.  Miocene goethitic and chamositic oolites, northeastern Colombia , 1979 .

[64]  B. Schmitz,et al.  Basaltic explosive volcanism, but no comet impact, at the Paleocene-Eocene boundary: high-resolution chemical and isotopic records from Egypt, Spain and Denmark , 2004 .

[65]  Karen A. Salamy,et al.  High‐resolution (104 years) deep‐sea foraminiferal stable isotope records of the Eocene‐Oligocene climate transition , 1996 .

[66]  A. Racey.  A REVIEW OF EOCENE NUMMULITE ACCUMULATIONS: STRUCTURE, FORMATION AND RESERVOIR POTENTIAL , 2001 .

[67]  F. B. Houten.  Review of cenozoic ooidal ironstones , 1992 .

[68]  Steven M Bohaty,et al.  Significant Southern Ocean warming event in the late middle Eocene , 2003 .

[69]  A. Plint,et al.  Tectonic and eustatic control on deposition and preservation of Upper Cretaceous ooidal ironstone and associated facies: Peace River Arch area, NW Alberta, Canada , 1999 .

[70]  W. Krumbein,et al.  Microbial structures in oolitic iron formations , 1986 .

[71]  H. Harder.  Mineral genesis in ironstones: a model based upon laboratory experiments and petrographic observations , 1989, Geological Society, London, Special Publications.

[72]  C. Dupuis,et al.  Environmental perturbation in the southern Tethys across the Paleocene/Eocene boundary (Dababiya, Egypt): Foraminiferal and clay mineral records , 2006 .

[73]  J. Zachos,et al.  Enhanced terrestrial weathering/runoff and surface ocean carbonate production during the recovery stages of the Paleocene‐Eocene thermal maximum , 2005 .

[74]  A. Pardo,et al.  Climatic evolution on the southeastern margin of the Tethys (Negev, Israel) from the Palaeocene to the early Eocene: focus on the late Palaeocene thermal maximum , 2000, Journal of the Geological Society.

[75]  K. Miller,et al.  The Phanerozoic Record of Global Sea-Level Change , 2005, Science.

[76]  G. Retallack.  Cool-Climate or Warm-Spike Lateritic Bauxites at High Latitudes? , 2008, The Journal of Geology.