PALYNO-SEQUENCE
STRATIGRAPHY
OF
CRETACEOUS/PALAEOGENE
SEDIMENTS OFFSHORE EASTERN BENIN BASIN, SOUTHWEST NIGERIA
Adeniran, O.A, Adeonipekun A. P., Nton E.
ABSTRACT
The onshore Eastern Benin Basin is well studied and abundant data with respect to its geology
and mineral resources are well known. However, unavailability of much data on the offshore has
limited exploration efforts in the offshore area. Additional knowledge of its geology will
encourage investing multinationals into this marginal basin. To contribute to this data gathering,
cuttings from a well, X-1, was studied so as to deduce the age, palynostratigraphy and
depositional environment history. Sub-samples of cuttings from Gbenga-1 were subjected to
standard palynological and sedimentological preparation techniques. Palynofacies analysis was
applied to substantiate paleoenvironmental deductions for the palyno-sequence stratigraphic
study. Recovered palynomorphs include: high occurrence of Canningia cf. senonica and
Nelsoniella and presence of Microdinium ornatum (dinoflagellates) and Crybelosporites
pannuceus and Cicatricosisporites spp. spores, and Classopollis spp. and Ephedripites
(sporomorphs) These occurrences suggest a late Cenomanian age while the occurrences of
Lejeunecysta hyaline, Selenopemphix selenoides and Hystrichokolpoma rigudae (dinoflagellates)
and Peregrinipollis nigericus, Retitricolporites irregularis and Ctenolophonidites costatus pollen
and Foveotriletes margaritae spore at the uppermost section indicate an Eocene age.
Paleoclimatic inferences indicate warm humid tropical climate conditions. Lithologically, the
basal sequence is composed of poorly sorted sandstones with variable interbeds of shales and
siltstones overlain by dark grey shales and interbedded limestones with occasional pyrite
occurrence. Overlying this is a glauconitic sequence consisting of shale with little clay and lenses
of limestones. The uppermost part is composed entirely of shales with some glauconitic
materials. Six lithofacies units with characteristic palynofacies assemblages and reflecting
different depositional environments were distinguished. The depositional environments varied
from estuarine through shallow inner neritic (shelf) to middle neritic shelf settings. With the
application of sequence stratigraphy, six sequences between the late Cretaceous and early
Tertiary stratigraphic column were recognized. Three main unconformities were identified with
the loss of lower Santonian, Coniacian and the Turonian.
Keywords ; Palynology, Palynofacies, Sequence stratigraphy, Dahomey basin
INTRODUCTION
The Dahomey basin is one of the sedimentary basins on the continental margin of the Gulf of
Guinea extending from the Southeastern Ghana in the west to the western flank of the Niger
Delta (Jones and Hockey, 1964; Ogbe, 1972; Omatsola and Adegoke, 1981). The eastern half of
1
the basin occurs within the Nigerian territory. Much of the works on Benin Basin were carried
out on onshore sediments and they have been published for quite some time. With the
availability of offshore samples, more precise evaluation can be made possible for better
understanding of this basin. Out of all these previous workers, Bilman (1992) was the only
published work on the offshore part. Bilman (1992) worked on offshore samples from the
Republic of Benin. His work offshore revealed some fundamental differences from what are
generally known about this basin onshore. Sediments representing post-Miocene, Oligocene, late
Eocene, late Senonian and Cenomanian were suspected absent in the Benin offshore area. Also,
four major unconformities were recognized by Bilman (1992). The knowledge revealed by this
effort would not have been made available if he had not studied the offshore.
The present study therefore attempts an integration of sedimentology, palynology and
palynofacies study with sequence stratigraphic principles over the cuttings to gain insight into
the stratigraphy of the basin in the offshore. This integration will enhance the deduction of age,
varying depositional environments, eustatic controls on the depositional sequences as well as the
paleoclimatic changes as documented in the Gbenga -1 well area
MATERIALS AND METHODS
The study area lies within latitude 0070381N- 0070401N and longitude 0030341E- 0030371E,
within the offshore eastern Benin Basin. It is located in water depths of between 325 feet and c.
3,000 feet and is 15 miles offshore being some 40 miles southwest of Lagos. It lies 24 km from
the coast in western Nigeria, on the border with Benin. It is situated 64 km from Lagos and close
to the West Africa Gas Pipeline (12 km away). Cutting were supplied by courtesy of Yinka
Folawiyo Ltd, Lagos.
A total of 210 ditch cuttings composited at an average of 18m (60ft.) from the studied well were used.
The ditch cuttings were examined under binocular microscope and analyzed to gather data on the
stratigraphic succession, textural and lithologic variations. The data was subsequently used to identify the
lithofacies associations. The ditch cutting samples, were processed to generate data for
palynostratigraphic and palynofacies interpretations. Extraction procedures relied on the acid resistant
nature of the recovered palynomorphs to remove the silicate and carbonate sediment matrix in which they
are embedded. The palynomorphs were qualitatively and quantitatively analyzed. The works of Jan du
Chene et al. (1978), Germeraad et al. (1968), Salard-Cheboldaeff (1991), Salami (1990) guided the
palynostratigraphy. Palynological Marine Index (PMI) Helenes et al. (1998), and the Peridinoids to
Gonyaulacoids ratio (P/G ratio) Harland (1973) were employed together with palynofacies study and
sedimentology in deducing the depositional environments. High values of PMI are interpreted as
indicative of normal marine depositional conditions. Low values of PMI are interpreted as brackish water
settings while zero value is interpreted as freshwater / terrestrial settings. The Peridinoid to
Gonyaulacoids ratio (P/G) introduced by Harland (1973) has been used to recognize paleosalinity
variations and proximity to shorelines. A peridinoid-dominated assemblage reflects low salinity and
nutrient-rich conditions (Jaminsky, 1995) and is related to near shore environments (Lagoonal, brackish
2
water). In contrast, low values of the ratio, i.e. Gonyaulacoids-dominated assemblages indicate open
marine environments.
Paleoclimatic reconstructions are based on the few species that survived to the present and on
those extinct species that are closely related to the extant ones. The paleoclimatic investigations
were based on selected palynomorphs that are well known indicators of Tertiary-Cretaceous
times. Moreover, investigations were also based on abundance of the pollen grains of the genus
Classopollis and fern spores. High abundance of Classopollis has been found to be related to arid
environments (Srivastava, 1976; Vakhrameev, 1981; Doyle et al., 1982; Lima, 1983).
Vakhrameev (1981) proposed climatic belts based on the abundance of Classopollis, where a low
abundance (1-10%) of the genus indicates a temperate climate, 20-50% warm subtropical, and
60-100% semi arid to arid conditions. In contrast, high abundance of fern spores reflects near
shore environments under humid conditions. This hypothesis is directly related to the importance
of humidity on the reproductive-cycle of modern pteridophytes (Doyle et al., 1982; Lima, 1983)
For palynofacies analysis, the kerogen (palynodebris) categories (Palynomaceral 1, 2, 3 and 4 as
well as amorphous organic matter - AOM) according to Oyede (1992) were counted and their
distribution trends and parameters were applied, based on percentages. Size variation of these
palynomacerals was also considered. The dispersed organic matter and palynomorph groups
identified include spores and pollen, fungal remains, freshwater algae, marine palynomorphs
(dinoflagellates and microforaminifera inner linings), structured phytoclasts (brown woody
materials and cuticles), unstructured phytoclasts (humic gel-like materials) black debris, and
amorphous organic matter.
RESULTS AND DISCUSSIONS
(A)
PALYNOLOGICAL DATA ANALYSIS
The succession studied yielded a rich palynomorphs assemblage, particularly the dinoflagellates
which are marine components forming 50.2% of the total palynomorphs assemblage in the well.
The second most abundant group is the pollen with 27.8%). The spores record 7.4% while the
fresh-water algae, Botryococccus records 13%. Foraminifera test linings are rare (1.6%).
PALYNOSTRATIGRAPHY
Dinoflagellates were mainly utilized for the biozonation of the studied interval because of their
short stratigraphic ranges and cosmopolitan nature. Sporomorphs (pollen and spores) were also
employed for better age resolution and boundary recognition. Six biozones informally designated
as AB 1 – AB 6 are defined. The zones are from bottom to top:
Biozone AB1
Interval: 2441m – 2204m
Age: ?Late Cenomanian
Definition: The top of this zone is defined by the base occurrences of Canningia cf.
senonicus and Dinogymnium spp. The base occurrence is most likely deeper than the base
3
of analysed interval (2441m). Also coinciding with the top of this interval is the top
occurrences of Classopollis spp. (pollen) and Cicatricosisporites spp. (spore). These
sporomorphs do not range beyond the Cenomanian.
Characteristic dinoflagellates recovered include Microdinium ornatum, Trithyrodinium
suspectum, and Ovoidinium spp., while that of sporomorphs include Gnetaceapollenites
bottenhagenii, Cretaceasporites scabratus, C. cf. polygonalis, Proteacidites signali and
Crybelosporites pannuceus as well as Leptolepidites verrucosus.
Since the top occurrence of spore C. pannuceus (top Cenomanian) coincides with the
base occurrence of dinoflagellate Dinogymnium spp. (base Santonian), it may be argued
that the Turonian is missing. Similarly, the non-recovery of Droseridites senonicus and
Syncolporites subtilis Lawal and Moullude (1982) also indicates the absence of
Coniacian. These observations mean that the top of Cenomanian is close to an
unconformity.
Biozone AB 2
Interval: 2204m – 2072m
Age: Santonian
Definition: The top of this zone is defined by the top occurrence of Canningia cf.
senonica at 2072m. Its base was recognized at 2204m by the base occurrences of
Dinogymnium spp. and Canningia cf. senonica. Characteristics dinoflagellates of this
zone include Dinogymnium gluminatrum, D. acuminata, Canningia cf. senonicus,
Nelsoniella spp., Deflandrea spp., and Trithyrodinium spp. Diagnostic sporomorphs and
their features include Buttinia andreevi, Ephedripites strigatus, abundant
Gnetaceapollenites boltenhageni, G. jansonii and abundant Syncolporites spp.
Biozone AB 3
Interval: 2072m - 1945m
Age: Campanian
The top of this zone is defined by the top occurrence of Dinogymnium cf. heterocostatus
at 1945m while the base is marked by the top occurrence of Canningia cf. senonica at
2072m. Characteristic dinoflagellates include D. acuminata, Chantagiella tripartite,
Ascodinium spp., Pterospermopsiss sp. Other important forms include Cyclopsiella
elliptica, Dioxya villosa, Cyclonephelium cf. chabaca, Batiacosphaera sp.
Characteristic sporomorphs include Buttinia andreevi, Leptolepidites verrucosus,
Foveotriletes spp. and Ephedripites spp as well as Deltoidosporites spp.
Biozone AB 4
Interval: 1945m – 1853m
Age: Maastrichtian
Definition: The top of this zone is marked by top occurrence of D. acuminata at 1853m
while the base was recognized at 1945m by the top ocurrence of Dinogymnium cf.
heterocostatum. Abundant occurrence of D. acuminata and occurrences of other species
4
such as Pterospermopsis sp., Trithyrodinium evitti, Wilsodinium sp. Deflandrea sp., and
Cyclonephelium spp. were recorded for this interval.
Characteristic sporomorphs include Proxapertites cursus, Longapertites spp. and
Foveotriletes margaritae, Deltoidosporites spp.
Dictyophillidites harrisii,
Auriculopollenites simplex and Rugulatisporites spp
Biozone AB 5
Interval: 1853m – 1645m
Age: Paleocene
Definition: The top of this zone is defined by the base of Lejeunecysta hyalina at 1645m
while the base was recognized by the top occurrence of D. acuminatum at 1853m.
The occurrences of Phelodinum sp. Polysphaeridium subtile, Spiniferites spp.,
Nematosphaeropsis
sp.,
Cordosphaeridium
callosum,
C.
microstriana,
Cordosphaeridium spp, Cleistosphaeridium sp, Gonyaulacacysta sp., Kallosphaeridium
spp. and Cyclonephelium spp. are characteristic of this age assignment. Other important
dinoflagellates are Deflandrea sp., Spiniferites ramosus, and Trithyrodinium evitti.
Characteristic sporomorphs within this zone include Longapertites retipilatus, L. psilatus,
Croton type, Psilatricolporites crassus (1750m), Gemmamonocolpites sp.
Brevitricolporites guineetii.
Biozone AB 6
Interval: 1645m – 1417m
Age: Late Eocene-Oligocene
Definition: The top of this zone is most likely shallower than the top of the analysed
interval at 1417m. Its base is marked by the base occurrence of Lejeunecysta hyalina and
top occurrence of Phelodinium sp. at 1645m.
Characteristic dinoflagellates recovered include Hystrichokolpoma rigaudae,
Protoperidinium spp, Peridinium spp, Impagidinium cf. sphaericum, Kallosphaeridium
spp, and Leiosphaeridim spp. Spiniferites spp. were also found in this zone.
Characteristic sporomorphs recovered include Retitricolporites irregularis,
Ctenolophonidites costatus, Longapertites marginatus, Proteacidites cooksonia,
Monoporites annulatus, Proteacidites cooksoni and Polypodiaceiosporites spp. (Pteris)
as well as Laevigatosporites spp.
The recovery of Peregrinipollis nigericus at 1463m however suggests the presence of a younger
age of probable Oligocene in the topmost part. The topmost interval 1463m – 1417m is however
rather too short to record other supportive features. Also Polypodiaceiosporites spp. and
Retibrevitricolporites sp. occur within this interval. The non-recovery of typical middle Eocene
pollen – Doualaidites laevigatus and the base occurrence of Verrucatosporites usmensis (late
5
Eocene to Recent) at 1615m may indicate that middle Eocene is missing. A finer biostratigraphic
sampling resolution at 10m may be needed to unravel this suspected loss.
(B)
PALEOECOLOGY AND PALEOCLIMATE
The palynomorph assemblages of the studied well, present diverse paleoecological
interpretations that reveal a progressive increase in marine influence in the area.
Classopollis makes about 20% of the pollen grains in the samples within the lowermost
section, although the relative abundance decreases markedly upwards of the section, the
proportion of ferns however increases upwardly to the top of analyzed interval. These
trends reflect the progressive increase of humid conditions as also seen in the occurrence
of some pollen like Longapertites, Spinizocolpites, Echitriporites, Syncolpites,
Clavatipollenites rotundus, Steveepollenites spp. Psilatricolporites crassus,
Caryapollenites spp., and Eucomidites spp. This scenario is indicative of warm humid
tropical climate in the study area as generally known for the late Cretaceous.
The PMI curves for the well shows very strong fluctuations. The PMI values indicate progressive
marine influence in the area. However terrestrial input into this environment is indicated through
major peaks of the P/G ratio. The general trend of values is such that the ratios approach the
value of 1.0 which indicates the predominance of the Peridinoids. The Peridinoid dominated
assemblage made up mainly of Protoperidinium, Leiosphaeridia spp, Nelsoniella sp,
Lejeunecysta hyalina, Kallosphaeridium spp. and Cyclonephelium spp, reflects low salinity and
nutrient-rich conditions related to near shore environments (Lagoonal, brackish water).
(C)
DEPOSITIONAL ENVIRONMENTS
In deducing the environments of deposition for the studied stratigraphic column, data from
palynofacies study, sporomorphs and marine indices (dinoflagellates and microforaminiferal wall
linings) were integrated with lithology. The palynofacies study as applied by Oyede, (1992) was
employed. The humic gel-like substances are referred to as Palynomaceral-1 (P1), Brown-orange
coloured woody materials are referred to as Palynomaceral-2 (P2), bouyant cuticular materials
are referred to as Palynomaceral-3 (P3), while black equidimentional, blade or niddle shaped
woody materials are referred as Palynomaceral-4 (P4). The structureless amorphous organic
matter is referred to as Amorphous Organic Matter - AOM. On the basis of sedimentological
parameters, five lithological units were recognized. The integration of palynological,
palynofacies and lithological data however led to the delineation of six environments of
deposition. (Figures ?, ? and ?) These depositional environments are briefly discussed below.
LITHOFACIES - 6 (2441-2313m)
6
This unit is made up of a sand:shale:silt ratio of 10:30:60. The sands are white, off-white to light
grey, very fine to fine grained, sub-angular to sub-rounded, moderately sorted, micromicaceous
and pyritic. The shales are light grey, sub blocky, soft to firm, very sticky and slightly
calcareous. Its silt contents are light grey, very soft to soft, sticky, firm to amorphous, slightly
calcareous, micromicaceous with traces of pyrites. Palynologically, the PMI value is low while
the Peridinoid/Gonyaulacoid ratio is high. These indices suggest a proximal marine setting.
However, the high amorphous organic matter (AOM), low humic debris (P1) and high
proportion of brown woods (P2) as well as the medium sized rounded to sub-angular
palynofacies are indicative of a proximal shallow marine setting in the upper shoreface.
LITHOFACIES – 5 (2313 -2277m)
Lithologic component of this unit is made up of a silt:sand ratio of 70:30. The sands are light
grey to off-white, very fine grained to fine grained, medium grained in part, subangular to
subrounded, moderately sorted, micromicaceous, and pyritic. The siltstones are light grey to grey
brown, very soft to soft, sticky, slightly calcareous and micromicaceous. Minor traces of shales
are present. PMI value is extremely low while P/G value is high. These indices combined with
high proportion of large-sized, rounded to angular humic debris, and low values of AOM
indicate a proximal fluvio-marine setting/nearshore estuarine setting.
LITHOFACIES -4 (2277-2112m)
This unit is characterized with the abundant proportions of sandstones in the range of 60 to 80%
while the siltstones vary between 20 and 40%. The sands are light grey brown, very fine to fine
grained, subangular to sub rounded with micromica. Siltstones here are light grey, medium,very
soft, sticky, and slightly calcareous. PMI values, sporomorph and gonyaulacoids proportions
improved tremendously over the underlying. Two fluvio-marine settings are recognizable on the
basis of the palynodebris. The lower section (2277 – 2170m) is proximal fluvio-marine as a
result of high values of angular P1 and P2 palynodebris as well as low values of AOM. Distal
fluvio-marine is indicated for the upper section as inferred from the extremely low humic debris
(P1) and P2 with characteristic high proportions of AOM.
.
LITHOFACIES – 3 (2112 – 1975m)
This unit is monolithic with 100% shale content. The shale is medium grey, light grey brown,
blocky to sub blocky, sub fissile, moderately firm to hard, earthly texture becoming very silty in
part, slightly calcareous with traces of pyrites. The PMI value in this unit is unprecedentedly
high, with progressive decrease in the proportion of humic debris < 19 while Amorphous organic
debris remained high > 65%. Continentally sourced sporomorphs (pollen and spores) and
freshwater Botryococcus are poorly represented. These indices together with the domination by
peridinoid dinoflagellates and the round-angular shaped palynodebris indicate a proximal
shallow marine setting possibly extending occasionally to the middle neritic.
7
LITHOFACIES – 2 (1975 – 1706m)
This unit is similar to the underlying in having wholly shaly except the presence of traces of
limestones. The shale varies from light through medium to very dark, blocky to sub blocky, sub
fissile, firm to moderately hard, earthy texture, slightly calcareous and silty. PMI values though
high, nosedived relative to underlying while Peridinoids/Gonyaulacoids ratio progressively
become reduced. These indices together with the lower proportion of well rounded humic debris
and correspondingly high AOM values indicate a distal to proximal shallow marine setting. The
palynodebris allowed the demarcation of lower (1975-1835m) and upper (1835-1706m) sections.
The lower is distal shallow while the upper is proximal in having improved recovery of brown
woody (P2) and humic (P1) materials with sub rounded to angular shape.
LITHOFACIES -1 (1706 – 1417m)
The light to medium grey shale with traces of pyrites in this unit is characterized by a
predominance of the terrestrial palynomorphs over the marine indices. The AOM content is high
with an average of 76%. The color of the organic matter ranges from brown to ash and are sub
angular to angular. Groundmass ranges between 20% and 35%. Proximal setting indicator,
cuticular debris (P3) occurred within this section. All debris groups are well represented. PMI
values are low with high Peridinoids/Gonyaulacoids ratio. These indices indicate a proximal
setting possibly a nearshore estuarine.
(D) Sequence Stratigraphy
In the application of sequence stratigraphic techniques to the studied section of the Aje-X
well, the work of Vail and Wornardt (1990) was adopted except that wire-line logs and
seismic lines as well as foraminiferal/nannofossils data were not available. However, the
available lithology/sedimentological parameters, sporomorphs and marine palynomorphs,
palynofacies and PMI values were employed. Due to non availability of electronic logs and
the generally more or less monotonous lithology, the variations in the values of AOM,
Palynomaceral-1(PM-1), and the PMI were relied upon based on the works of Tyson
(1995). Tyson and Follows (2000) reported that palynofacies data allowed distinguishing
landward from basin ward depositional shifts. From Tyson (1995), values of Humic gellike debris (PM-1) are directly proportional to AOM and inversely proportional to that of
PMI. See Fig. -? This relationship was adopted in the interpretation of this well.
8
Schematic relationship between organic matter abundance throughout a stratigraphic sequence
(Tyson, 1995)
The sequence stratigraphic analysis of this well led to the recognition of six sequences beginning
in the late Cretaceous with an HST and ending in the Tertiary with a TST.
Each Lowstand systems tract (LST) characteristically has abundant humic gel-like
Palynomaceral -1 (Ph), very low values of PMI and AOM. The Transgressive systems tract
(TST) has increasingly high values of PMI and AOM, while Palynomaceral-1 values are
decreasingly low. Within the Highstand systems trac (HST), AOM and PMI decrease from a high
to the lowest point while humic gel-like P1 (Ph) increases from the lowest value to the highest.
Maximum Flooding Surfaces were recognized at the lowest values of Palynomaceral -1 (Ph) and
highest values of PMI and AOM. Sequence Boundaries were picked at the lowest values of AOM
and PMI as well as highest values of humic gel-like Palynomaceral -1. See Fig.-?
A significant observation is the rounded shapes of the debris at virtually all the maximum
flooding surfaces.
Below are the recognized sequences with their candidate maximum flooding surfaces and
sequence boundaries as well as their equivalent ages according to Haq et al. (1987).
Sequence -1:
Sequence -2:
Sequence -3:
Sequence -4:
Sequence -5:
Sequence -6:
2414 – 2405m HST1
2405 – 2332m LST2, 2332 – 2259m TST2, 2259 – 2222m HST2
2222 – 2128m LST3, 2128 – 2109m TST3, 2109 - 2072m HST3
2072 - 2054m LST4, 2054 – 1999m TST4, 1999 - 1835m HST4
1835 – 1767m LST5, 1767 – 1676m TST5, 1675 – 1583m HST5
1583 – 1523m LST6, 1523 – 1414m TST6
9
Maximum flooding Surfaces
1. MFS2 2259m
2. MFS3 2109m
3. MFS4 1999m
4. MFS5 1676m
5. ?MFS6 1414m
Sequence Boundaries
1. SB2 2405m
2. SB3 2222m
3. SB4 2072m
4. SB5 1835m
5. SB6 1583m
Absolute Age
…93.5 Ma…
…86.0 Ma…
…84.0 Ma…
..?53.5 Ma…
..?52.5Ma….
Absolute Age
…94.0 Ma… sequence boundary
…93.0 Ma… main seq. boundary (unconformity 1)
…85.0 Ma… sequence boundary
…83.0 Ma.... main seq. boundary ( unconformity 2)
…53.0 Ma… main seq. boundary (unconformity 3)
From the sequence stratigraphic interpretation of the sediments of this well, the suspected loss of
the lower Santonian, Coniacian and the Turonian sediments from the biostratigraphic data
inferences has been confirmed. Likewise, the absence of the upper and middle Maestricthtian is
also confirmed. This is one of the important values of sequence stratigraphy not only in oil
exploration and production but also in paleoclimatic and paleobotanical studies. For a missing
section in a sedimentary column may represent an important paleoclimatic regime, and when not
recorded due to erosional activity or faulting, wrong interpretation and conclusion may be made
and reached respectively. Billman (1992) suspected the absence of Cenomanian and late
Senonian in the offshore Badagry sediments he studied. This suspicion may be restricted to the
immediate locality of the well. This is because in this present well, the Cenomanian is present
and also the late Senonian represented by early Campanian, while the early Senonian and even
the whole of Turonian are absent based on inferences from well preserved and abundant
sporomorphs and dinogflagellates. The observed absence of these sections led to the recognition
of three major unconformities, two in the late Cretaceous and one in the early Tertiary.
SUMMARY AND CONCLUSIONS
The palynological, palynofacies and sequence stratigraphic analyses of studied
Cretaceous/Paleogene sediments of Benin Basin allowed the detailed palyno-sequence
stratigraphy and reconstruction depositional of the succession studied. The offshore sediments
straddle the late Cenomanian / early Eocene age. Loss of the lower Santonian, Coniacian and the
Turonian is evident from this work. Upper and middle Maestritchtian are absent from the locality
of the studied stratigraphic column. The sequence stratigraphic interpretation complemented the
10
palynostratigraphy in recognizing these features. The depositional environments changed from
marginal marine (estuarine) through shallow inner neritic to middle neritic shelf settings
LITHOSECTION OF AJE-X
11
PALYNOMORPHS ZONATION AND AGE OF WELL
12
PMI AND P/G VARIATIONS ALONG THE SAMPLE DEPTH INTERVALS
13
PALYNOFACIES PROFILE OF AJE-X WELL
14
SEA LEVEL INTERPRETATION OF AJE-X WELL
15
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