1) New stratigraphic data shows that oolitic facies in Oman referred to as the "Habshan Formation" are actually of Hauterivian to Early Barremian age, and are thus part of the Lekhwair regional stage rather than correlated to the type Habshan of Abu Dhabi. 2) The Hawar interval in Oman and the UAE represents discrete third-order depositional sequences, with the Oman section showing a thin transgressive systems tract and thick highstand systems tract, reversed from the thick transgressive and thin highstand pattern in the UAE. 3) Key biostratigraphic markers like the foraminifer Choffatella help

1. New stratigraphic data
on the Lekhwair(ian) and Hawar(ian) regional
stages of the
Lower Cretaceous in Oman
Bruno Granier
Bernard Pittet

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. 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. 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. 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. 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. 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. 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. 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. "Habshan" (Oman)"Habshan" (Oman)
In Oman (in most outcrops) microfossil assemblages of the
so-called "Habshan" are of Hauterivian and Early
Barremian age.

11. "Habshan" (Oman)"Habshan" (Oman)

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. 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. 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. 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. 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. HawarHawar
However Choffatella is
restricted to the first
five meters of this
onland unit.

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. 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. 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. 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