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New stratigraphic data on the Lekhwair(ian) and Hawar(ian) regional stages of the Lower Cretaceous in Oman

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Talk given on the occasion of STRATI2010 - the 4th "French" Congress on Stratigraphy (August 30, 2010 – September 2, 2010) in Paris ... that was also the issue #0 of the later International STRATI_s!

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New stratigraphic data on the Lekhwair(ian) and Hawar(ian) regional stages of the Lower Cretaceous in Oman

  1. 1. New stratigraphic data on the Lekhwair(ian) and Hawar(ian) regional stages of the Lower Cretaceous in Oman Bruno Granier Bernard Pittet
  2. 2. IntroductionIntroduction Although the type sections of most stages of the Kahmah series of the Middle-East regional succession were recently revised and the definitions of their upper and lower boundaries were either definitively legitimized or slightly emended, some authors continue to use incorrect information and to make interpretations therefrom that are in conflict with the valid data now to hand.
  3. 3. IntroductionIntroduction We present here new stratigraphic findings concerning the Lekhwair(-ian) and Hawar(-ian) regional stages of the Lower Cretaceous in (the U.A.E. and) Oman.
  4. 4. IntroductionIntroduction We present here new stratigraphic findings concerning the Lekhwair(-ian) and Hawar(- ian) regional stages of the Lower Cretaceous in (the U.A.E. and) Oman.
  5. 5. LekhwairLekhwair In Oman oolitic facies are interfingered in the outer platform to slope facies of the Salil Formation. These shoal facies (yellow) are diachronous for they record the seaward shift of successive progradational wedges (see Lebec, 2004), a migration caused by regular or forced regressions.
  6. 6. LekhwairLekhwair In Oman these oolitic facies are referred to as the "Habshan Formation". This so-called "Habshan Formation" of Oman was mistakenly correlated with the type Habshan of Abu Dhabi (Hassan et alii, 1975; Simmons, 1990...).
  7. 7. LekhwairLekhwair In Oman these oolitic facies are referred to as the "Habshan Formation". This so-called "Habshan Formation" of Oman was mistakenly correlated with the type Habshan of Abu Dhabi (Hassan et alii, 1975; Simmons, 1990...).
  8. 8. Habshan (UAE)Habshan (UAE) In its type locality, well Zakum-1 of the Abu Dhabi offshore, oolitic (grain-supported) facies are rare in the predominantly mud- supported microfacies (characteristic of the innermost parts of the platform)
  9. 9. Habshan (UAE)Habshan (UAE) Microfossil (calcareous algae and foraminifers) assemblages are either of Tithonian and Berriasian age in the Habshan as defined by Hassan et alii (1975) or they are restricted to the Tithonian alone in the Habshan as emended by Granier (2000).
  10. 10. "Habshan" (Oman)"Habshan" (Oman) In Oman (in most outcrops) microfossil assemblages of the so-called "Habshan" are of Hauterivian and Early Barremian age.
  11. 11. "Habshan" (Oman)"Habshan" (Oman)
  12. 12. "Habshan" (Oman)"Habshan" (Oman) In Oman (in most outcrops) microfossil assemblages of the so-called "Habshan" are of Hauterivian and Early Barremian age. Therefore, in Oman the time- span of the so-called "Habshan" is actually within that of the Lekhwair regional stage.
  13. 13. HawarHawar In the ADMA offshore field 'A' (Granier et alii, 2003), the Hawar is a 25' thick depositional sequence: most of it was laid down as a transgressive systems tract, but the uppermost 2.5, a thin shaly interval was deposited during a highstand systems tract.
  14. 14. HawarHawar As stated by Granier (2008): "The upper limit of the Hawar Formation is coincident with an abrupt change in sedimentation from the uppermost shale (...) to very shallow-water carbonates (...). As does the lower boundary, the upper one records a forced regression: the fall in sea level can be estimated to have been 40 meters or more". To date most authors have overlooked this major sequence boundary. - marine +
  15. 15. HawarHawar To date most authors have overlooked this major sequence boundary. But they also did not recognize other key markers. For instance, the occurrence of the foraminifer Choffatella in the upper half of the TST support its use as an index characterizing relatively deeper-water environments.
  16. 16. HawarHawar In Oman, at Wadi Bani Kharus, the Hawar interval attains a thickness of 25 meters (van Buchem et alii, 2002), more than three times that of the time- equivalent section in the Emirian offshore field.
  17. 17. HawarHawar However Choffatella is restricted to the first five meters of this onland unit.
  18. 18. HawarHawar However Choffatella is restricted to the first five meters of this onland unit. This fact contradicts sequential interpretations of authors who consider the Hawar to be either the TST of a higher scale sequence extending into the Shu'aiba or the lower part of this TST. Not there There
  19. 19. Granier et alii (2010) defined the maximum flooding surface of the Hawar sequence to be near the 5 meter mark. With respect to stratonomy, the Hawar sequence is highly asymetrical in Oman. Its pattern is reversed from that of field 'A' (thick TST and thin HST): at Wadi Bani Kharus the TST is thin and the HST is thick. HawarHawar
  20. 20. These new biostratigraphic data: 1) document -- if needed -- the diachronism of the prograding clinoforms (i.e., they allow to « date » them in the Lekhwair time-equivalent) SummarySummary Older H?< shoals Younger H?> - B?< shoals
  21. 21. These new biostratigraphic data: 1) document -- if needed -- the diachronism of the prograding clinoforms (i.e., they allow to « date » them in the Lekhwair time-equivalent) 2) help us to understand the discrete stratal patterns observed in the Hawar (i.e., one third- order depositional sequence) in two localities, one in the UAE and one in Oman. We thank Manu Dujoncquoy and Philippe Razin for providing us some material. SummarySummary Older H?< shoals Younger H?> - B?< shoals

Notizen

  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
  • after the publication of an article by A. Strasser (1986), my former colleague, Robert Boichard (TOTAL), focused his attention on ooid microstructures. He found that at the base of the &amp;quot;Dalle Nacrée&amp;quot; the ooids are radial, grade upward to concentric in the middle and are micritic at the top. This demonstrates a gradual change in the bio-physico-chemical conditions under which they were formed.
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