Agglutinated Middle-Upper Eocene foraminifera in Jabal Hafit, Al ...

22 H. S. ANAN
The species was recorded from the Paleocene to Middle
Eocene of Italy (PROTO DECIMA & de BIASE, 1975) and
from the Lower Eocene of Norwegian Sea, DSDP Site
338 (HULSBOS et al., 1989).
It occurs in the top Middle Eocene (P14 and P14/15) of
Jabal Hafit.
V. TEMPORAL DISTRIBUTION AROUND M/U
EOCENE BOUNDARY
According to many authors (ex. VAIL et al., 1977 ; HAQ et
al., 1987) a marked fall in the eustatic sea level took place
at the end of the Middle Eocene (39-40 Ma). This global
regression may also has taken place in the Al Ain area. It
may caused the deposition of the phosphatic limestone bed
(bed no. 9, Fig. 2 ; about 25 m thick), which represents the
passage interval between the Middle and Upper Eocene
succession in the study section. Previously, ABUL-NASR
& THUNELL (1987) noted that the concentration of clastic
phosphatic sediment being a function of reworking during
times of lowered sea level.
The temporal distribution of the fifteen identified species
in the Middle-Upper Eocene succession of the study
section is shown in Fig. 3. The following remarks are
presented :
1. The diversity of the identified species gradually
decreases upward throughout the M/U Eocene
succession. About 87 % of the identified species
(13/15 species) are recorded in the Middle Eocene
compared to 53 % (8/15 species) in the Late Eocene.
It is interesting to note that the M/U Eocene boundary
in Egypt (ANAN, 1994b) is also marked by a sudden
fall in abundance and/or diversity of the foraminiferal
assemblage.
2. Seven out of the identified species are recorded only
from the Middle Eocene zones (P14 and P14/15).
These species are : Ammobaculites cubensis,
Bathysiphon saidi, Haplophragmoides walteri,
Miliammina kenawyi, Plectina emiratensis and
Textularia plummerae, T. communis.
3. Two species Tritaxia alpina and Vulvulina jarvisi are
restricted to the Late Eocene (P15 and P16).
4. Six out of thirteen Middle Eocene species continue
into the Late Eocene (P15 and P16). These are :
Bathysiphon eocenicus, Dorothia nacataensis,
Marssonella hafitensis, Orbulinelloides arabicus,
Spiroplectinella nuttalli and Vulvulina haeringensis.
5. Four species B. eocenicus, O. arabicus, M. hafitensis
and D. nacataensis, among other species, have a long
ranged throughout the M/U Eocene horizon, and
represent the Tle5 succession.
VI. PALEOBIOGEOGRAPHY AND
PALEOECOLOGY
The paleogeographic reconstruction maps of MOORE et
al. (1978) and ZACHOS et al. (1993) for the Middle-Late
Eocene show that the Tethyan realm extended to the
southeast and had been connected with the Indo-Pacific
realm via a seaway separating Arabia from Iran-India
region. At that time, the North America and South
America were separated and the Atlantic and Pacific
realms connected by another seaway. On the other
hand, CHERIF & EL DEEB (1984) noted that close to the
end of the Middle Eocene the previously arid climates
became markedly wetter and seems also to have been
accompanied by a cooling of the water temperature.
They also suggested that the climatic changes inferred
from the Hafit area seem to have been widespread, at
least in parts of the Middle East. KELLER et al. (1987)
noted that the Middle/Late Eocene boundary is marked
by expansion of cooler water assemblages and a major
extinction event among warmer water species involving
80 % of the individuals of the population, or 23 % of the
species population.
Table I shows the identified fifteen agglutinated
foraminiferal species in the Middle-Upper Eocene
succession from Jabal Hafit, as well as, the other
recorded species from Egypt, Italy, Caribbean region and
Ecuador by different authors. The following remarks can
be presented :
1. The study section yields 15 agglutinated foraminiferal
species around the M/U Eocene boundary, compared
to 13 species from Egypt, 19 from Italy, 17 from
Caribbean region and 13 species from Ecuador
(Pacific realm).
2. Seven species : Ammobaculites cubensis, Bathysiphon
eocenicus, B. saidi, Haplophragmoides walteri,
Miliammina kenawyi, Spiroplectinella nuttalli and
Textularia communis are recorded from both Jabal
Hafit (UAE) and Egypt in one hand, while only
four species Ammobaculites cubensis, A. subglabra,
Bathysiphon eocenicus and Textularia recta are
recorded from both Egypt and Italy (Tethyan realm)
in the other hand.
3. Eleven species Dorothia colei, D. nipeenis,
Gaudryina pseudocollins, Haplophragmoides
emaciatus, Karreriella hantkeniana, K. subcylindrica,
Lituotuba navetensis, Martinottiella petrosa,
Plectina dalmatina, Pseudoclavulina trinitatensis
and Spiroplectammina trinitatensis are endemic to
Caribbean region.
4. Three species Ammobaculites cubensis, Bathysiphon
eocenicus and Haplophragmoides emaciatus are
recorded in both the Tethyan and Caribbean regions.
5. Two species Ammodiscus incertus and Bathysiphon
eocenicus are recorded from both the Caribbean
region and Ecuador.
6. Only one species Spiroplectinella nuttalli is recorded
in UAE, Egypt and Ecuador.