‫ميحرلا نمحرلا هللا‬ ‫بسم‬

Omdurman Islamic University

Faculty Of Science And Technology
Geology Department
Dissertation submitted partial fulfillment for the
Requirements of B.sc
Titled:
Study of the ancient sedimentary environments of the
Rawat field with applications of palynology
Prepared by:
Abdelazim Mohamed zakaria Thabit
Altayeb Alsaddig Mansour Altayeb
Bashir Muddathir Bashir Abdallah
Mohammed Yousuf Ali Abd elgadder
Osman Abdelfattah siddig Ahmed
Osman Elsserag Ahmed Abdelrahman

Supervised by:
Dr.Saddam Hassan Mohammed Ahmed

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 ‫اآلية‬
‫[ يأيها الذيه ءامىىا اتقىا هللا وءامىىا بزسىله يؤتكم كفليه مه رحمته‬
‫ويجعل لكم وىرآ تمشىن به ويغفز لكم وهللا غفىر رحيم ]‬
‫صدق هللا العظيم‬
‫سىرة الحديد (‪)82‬‬

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 ‫الخالصة‬
‫مىطمخ انذساعخ ًٌ حُض انشاَاد األخذَدي انزي ٌمع فً انجضء انجىُثً‬
‫نهغُدان ‪ٌ ,‬زي انذساعخ مشكضح عهى رحذٌذ انجٍئخ انزشعٍجٍخ انمذٌمخ نمعشفخ‬
‫انجٍئبد انغبئذح فً األصمىخ انجٍُنُجٍخ انغبثمخ َرحذٌذ إحزمبنٍخ رُاجذ‬
‫انىفظ‪.‬‬
‫رم انزعشف عهى ثمبوٍخ ركبٌَه سعُثٍخ ثحُض انشاَاد ًٌَ ربخز وفظ‬
‫أعمبء انزكبٌَه انشعُثٍخ ثحُض مهُط انشمبنً ‪ َ .‬انزكبٌَه ًٌ مه‬
‫األعفم نألعهى (جهحبن‪ ،‬مهُط‪ٌ ،‬بثُط‪ ،‬عذاس‪ ،‬جٍمٍذي‪ ،‬مٍبدَل‪ ،‬دالب‪،‬‬
‫الُس) ‪.‬‬
‫َعهى حغت رفغٍش معهُمبد مجغبد اَثبس انزً أعزخذمذ فً انذساعخ‬
‫َجذ أن انحُض امزأل ثشعُثٍبد رزشعت أغهجٍب عه طشٌك االوٍبس َ‬
‫انجحٍشاد ‪.‬‬
‫َرم إجشاء دساعخ مجٍشٌخ نعٍىبد األثُاغ َ حجُة انهمبح نهجئش َانزً رم‬
‫جمع عٍىبرٍب ثُاعطخ ششكخ انشاَاد نهجزشَل َرمذ انذساعخ َ انزحهٍم فً‬
‫مخزجشاد انىفظ انمشكضٌخ َأثجزذ انذساعخ أن وُع انكٍشَجٍه فً انجئش مه‬
‫انىُع انثبوً ‪.‬‬

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 Acknowledgement
Firstly, we would like to thank Allah to help us to make this thesis.
Then, we thank Dr. Saddam Hassan Mohammed Ahmed for this
kindsupervision and valuable guidance.
Sincere thanks and gratitude to:
Dr.Omer Elniemaa Arbab , and all staff members of Geology
Department and faculty of Science, Omdurrman University. Also my
thanks extend to Dr. Ali Eisawi, all the staff member of the
Biostratigraphylab at PLRS ; Mr. Abdalbagi, Shaa-Eldin, Ammar, Dr.
Hussein Bashir the head of the Geology Department of PLRS -Ministry
of Petroleum and Gas. we send all the Thanks, Sincerity, and Respect for
all of them and to any Person who helped us.

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CHAPTER ONE ……………………………………………….. )9)
INTRODUCTION ………………………………………….……. (10)
Location…………………………………………………………… (10)
Accessibility………………………………………………………. (11)
Statement of the Problem………………………………………….. (12)
Objectives of the study…………………………………………….. (13)
CHAPTER TWO…………………………………………….…… (15)

STRATIGRAPHY OF THE RAWAT SUB BASIN

General……………………………………………………………… (16)
Rawat Formation (Campanian or older-? Late Maastrichtian).……. (17)
Yale Formation……………………………………………………… (21)
Adar Formation………………………………………………...…… (22)
Jimidi Formation…………………………………………..……….. (23)
Miadol Formation…………………………………………………… (23)
Daga Formation……………………………………...……………… (24)
Agor Formation………………………………………...…………… (25)
Stratigraphic subdivisions of the southern Rawat Sub Basin……… (25)
Garjak Formation…………………………………………………… (26)

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Nuer Formation………………………………………………...…… (27)
Tectonic setting…………………………………………………….. (28)
CHAPTER THREE……………………………...………………. (31)
PREPARATION TECHNIQUES AND METHOD OF STUDY
Technique……………………………………………..…………... (32)
Pre-chemical Treatment……………………………..……………. (32)
Crushing………………………………………………..…………. (33)
Chemical Treatment…………………………….………………… (34)
Removal of Carbonate……………………………….…………… (34)
Removal of Silicate……………………………….………………. (35)
Oxidation of Organic Matter………………………….…………... (35)
Alkali Treatment………………………………………….……….. (36)
Post-chemical Treatment……………………………….…………. (36)
Ultrasonic Treatment…………………………………….………... (36)
Concentration of Palynomorphs………………….……………….. (37)
Staining of Palynomorphs……………………………………....… (38)
Slide Preparation………………………………………….………. (39)
Method of Study and Image Processing………………….……..… (40)
Palynomorph Identification and Counting…………………....…… (41)
Image Processing………………………………………………..… (41)
CHAPTER FOURE………………………………………..…….. (42)
MATERIAL AND PALYNOLOGICAL METHOD
CHAPTER FIVE……………………………………………..…... (57)
PALAEOENVIRONMENTAL INTERPRETATIONS

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RAWAT WEST-1 PALEOENVIRONMENTS………..………….. (58)
MUGUD-1 WELL PALEOENVIRONMENTS………….………... (60)
WATEESH-1 WELL PALEOENVIRONMENTS………..……… (62)
DURRA-1 WELL PALEOENVIRONMENTS……………..……. (64)
SHAWA-1 WELL PALEOENVIRONMENTS………….………. (65)
TAKA-1 WELL PALEOENVIRONMENTS……………….……. (67)
EAST ANGARA-1 WELL PALEOENVIRONMENTS…….…… (68)
CHAPTER SIX…………………………………………...……… (71)
CONCLUTION

Summary ……………………………………………………….… (72)

Conclusion…………………………………………………….….. (73)

Recommendations………………………………………………… (74)

References………………………………………………………..... (75)

List of Figures
Fig. 1.1: showing the location of Rawat basin……………………... (10)

Fig. 1.2: showing the drainage system of the study area…………... (12)

Fig 2.1: lithological log of the studied boreholes…………………… (19)

Fig. 2.2: regional strtigraphic correlation………………………........ (29)

Fig. 2.3: Structural map showing the major rift basin………………. (30)

Fig. 3.1: ditch cutting sample at 1617 m……………………………. (32)

Fig. 3.2: showing the sample before chemical treatment…………… (33)

Fig. 3.3: the Beaker…………………………………………………. (33)

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Fig. 3.4: the Ultrasonic……………………………………………… (37)

Fig. 3.5: showing Centerfuge ………………………………………. (38)

Fig. 3.6: the Heater………………………………………………… (40)

Fig. 3.7: showing the slide after preparation……………………… (40)

Fig. 4.1: sample of spores and pollen grain……………………….. (56)

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CHAPTER ONE

INTRODUCTION

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1.1 Introduction:
The geology of the Sudan is extremely diverse with a variety of
metamorphic, igneous and sedimentary rocks. The oldest sedimentary
basins encountered sofar in Sudan are of Cambro-Ordovician age. These
occur within narrowgrabens formed by rifting, which preceded
consolidation of Pan African structures in north and northwestern Sudan
(Whiteman, 1971). Much attentionhas been given to an already explored
Mesozoic and Cenozoic rift related basins, in the south and central
Sudan.
1.2 Location:
The Rawat sub Basin lies in the northern part of Block 25 in Sudan,
around 350 km south of Khartoum City between latitudes 11.6 – 12.8 N
and longitudes 31.6– 32.9 E (Figs. 1.1 & 1.2). It is located around 400
km to the southeast of the CASZ and represents the northern extension
of the Rawat sub Basin. It is up to 175km long and 50 km wide and
locally contains up to 6000 m of Upper Cretaceous to Neogene
Sediments.

Fig: 1-1 showing the location of the Study area

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1.3Accessibility:
The Study area can be accessed by a variety of transportation means
depending on the weather conditions, and season. Vehicles and trucks
are suitable during the arid seasons, but in autumn air crafts are used.
The White Nile remains the traditional waterway for streams from
Rabak to Rawat.

1.4 Statement of the Problem

Two oil fields were discovered in the Rawat basin but were not
developed. Thereservoir geometry and continuity adopted in the study is
not well understoodin this basin. Sequence stratigraphic approach will
help understanding the basincharacterization and reservoir properties
which have the advantages inassessing and adopting suitable production
technology.The present study is an integration of the evolution of the
sedimentaryenvironments with age deduced from the palynological
evidence, lithology, andelectrofacies analysis all guided by seismic. This
study will be focusing in thesubsurface facies analysis including
sedimentological and palynologicalinterpretations which are
incorporated in a stratigraphic framework. Theintegration of
sedimentological model and stratigraphy will allow betterunderstanding
of sediment architecture and facies mapping and correlation.This in turn
helps in answering many questions related to development
andmanagement of reservoir rocks.
isolated sandstone outcrops east of Muglad town, the Rawat sub basin
and the surrounding areas are essentially flat land coverd by superficial
deposits of Quarternary age the area has a mean ground elevation of
about 395 m above sea level and the difference between the highest and
the lowest places is less than 15 m. the drainage system is generally
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towards the northwest, of which the White Nile and its tributaries
represent the main drainage system

Fig: 1-2 showing drainage system of the study area

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1.5 Objectives of the study:
The majority of exploration activities in Sudan were focused on three
main rift systems: the Muglad, Melut and Blue Nile basins, which show
an overall NW-SE and NS striking direction nearly perpendicular to the
Central African Shear Zone (CASZ). Most of the geological works
carried out around the Rawat Basin were focused on exploration for
minerals. Whiteman (1971) and Vail (1978) described the geology of
the study area and the adjacent territories in the general context of the
geology of the Sudan. The southern Blue Nile and adjacent areas
received considerable attention in1980s by GRAS in collaboration with
the University of Portsmouth, UK and the University of Hannover,
Germany because rocks bearing gold, chromite and other minerals of
economic values crop out there. Kabeh, (1961: in Bakr, 1995) reported
on the geology of the Ingessana hills and economic minerals potential.
Several papers have provided information about the general
configuration of the various grabens in Sudan (e.g. Salama, 1985; Prasad
et al., 1986; Schull,1988; Bosworth, 1992; Mohamed et al., 1999).
Schull (1988) and McHargue et al. (1992) have recognized three major
episodes of rifting, concomitant subsidence and non-marine/non
volcanic sedimentation. These three rifting periods are (140 to 95 Ma
(F1), 95 to 65 Ma(F2), and 65 to 30 Ma (F3)
Sedimentological investigation of the Kurdofan group of the Rawat sub
basin wascarried out by El-Tayeb (1993) while Bakr (1995) studied the
Mesozoic andCenozoic sedimentary facies of the Muglad, Melut and
Blue Nile basins. According to Kaska (1989) a five spore and pollen
zonation was established for the Muglad, Melut and Blue Nile basins.
The Upper Cretaceous to Neogene non-marine sequence of the Rawat
Rift sub Basin in the southeastern Sudan was palynologically
investigated by Eisawi B(2007). Based on seismic and well log

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interpretations carried out by RRI(1991) seven formations have been
proposed for the Northern Rawat sub Basin. Lithostratigraphic
subdivisions, biostratigraphic dating and palaeoenvironmental
interpretation for the various sedimentary units of the Northern Rawat
sub Basin have been established. Age assignments and
palaeoenvironmental interpretations are mainly based on
spores/pollenassemblages.

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 CHAPTER TWO

STRATIGRAPHY OF THE RAWAT SUB

BASIN

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2.1 General
During the last few years, Petrodar has conducted new drilling in the
Rawat sub basin but the acquired data ire considered confidential. Such
information would help considerably in better understanding the
itratigraphy of the basin and could provide a guide for correlation not
only within the Rawat sub Basin but also over a regional scale.
None of the five wells drilled by Chevron in the study area has reached
basement. However, recently drilled well at the flank of the Rawat sub
Basin has penetrated marble at approximately 1360 m depth (Tamarat,
personal communication). The marble is unconformably overlain by
Late Cretaceous sediments. According to Schull (1988), the area
occupied by the Central Sudanese Rift Basins including the study area,
was an extensive continental platform from the Cambrian to the
Mesozoic, which had become a consolidated and stabilized platform by
the end of the Pan-African episode (approximately 550 Ma). Schull's
interpretation may explain the absence of Paleozoic and Early Mesozoic
sediments within the sequence of the Sudanese rift basins.
Until now, nothing has been published on the detailed lithostratigraphic
subdivisions of the sedimentary strata in the study area. Informal
lithostratigraphic nomenclature for the sequence of the RAwat sub
Basin was first proposed by Chevron Overseas Petroleum Inc (1982).
Two major sedimentary groups were introduced: The Kordofan Group
spanning the Quaternary and Tertiary times and the Samaa Formation
(Upper Cretaceous).
Robertson Research International (R.R.I) and the Geological Research
Authority of the Sudan (GRAS), in an unpublished report (1991), re-
evaluated Chevron's work and introduced more subdivisions for the
sedimentary sequence in the Rawat sub Basin. As a result, a broad
lithostratigraphic correlation proved possible between wells in the
northern Rawat sub basin (AY-1, AY-2 and AY-3). However, the AY-4
well in the south shows unique lithological subdivisions; hence, a
different lithostratigraphic framework has to be introduced.
Consequently, the northern part of the basin was subdivided into seven
formations, while eight formations were introduced for the southern part.
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In the following sections, reference should be made to Figure 6 for
lithology and formation boundaries. The above-mentioned stratigraphic
schemes for the northern and southern parts of the Rawat sub Basin will
be discussed in the following sections.

2.2 Stratigraphic subdivisions of the northern Rawat Sub Basin

Out of five wells drilled by Chevron in the Rawat sub Basin, four wells
(encrypted herein as AY-0, AY-1, AY-2 and AY-3) are located in the
northern part of the basin; the fifth well (AY-4) is located in the south
(Fig. 1).
Based on seismic and well log interpretations (RRI & GRAS, 1991)
seven formations have been proposed for the northern Melut Basin
(Table 1). In the following section, a brief account will be given
regarding lithostratigraphic subdivisions, biostratigraphic dating and
palaeoenvironmental interpretation for the various sedimentary units of
the northern Melut Basin. Lithostratigraphic nomenclatures, type and
reference sections are those introduced by RRI & GRAS (unpublished
reports, 1991). Age assignments and palaeoenvironmental
interpretations are based on spores/pollen and other palynomorphs
identified in the present work.
2.3 Rawat Formation (Campanian or older-? Late Maastrichtian)
Type and reference section: well AY-1, 1534-4544.6 m (RRI & GRAS,
1991)
The formation is identified in the three wells in the northern Rawat sub
Basin. It is of variable thickness, ranging from 3010.5 m in AY-1 to 450
m in Yale-1 (Fig. 6). Lithologically, the Rawat Formation consists of
interbedded sandstones and clay stones with occasional thin siltstones.
Claystones are soft to hard, massive to sub-fissile, predominantly light-
to medium-grey and greyish-red and non calcareous. Sandstones are
white to yellowish-grey, showing variable grain size, generally
decreasing downhole in well AY-1. Approximately 60' thick andesitic
tuffs occur within the formation and dated as Campanian (RRI & GRAS,

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1991). Traces of carbonaceous material occur throughout the formation
and occasional ironstone nodules are recorded in well AY-3.
The upper boundary of the formation is highlighted on logs by an
upward increase in sonic interval transit time and decrease in gamma ray
response (Fig. 6). The lower boundary is not identified since the three
studied wells in the northern Rawat sub Basin reached total depth within
the formation. The Rawat Formation is subdivided herein into three
informal units based on lithological character inferred from log pattern.
The identified units (designated I, II & III) are discussed in an ascending
order from old to young as follows:

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Fig 2.1 Lithological logs of the studied boreholes based on composite
logs interpretation (R R I & GRAS,1991) and position of palynological
samples.

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Table 2.1 previous palynological dating versus present work ,northern
Rawat sub Basin
Formation RRI GRAS 1991 Present work
Agor Neogene – Quaternary Plestocene – Recent
Daga Upper Miocene – Late Miocene – Pliocene
Quaternary
Miadol Basal Lower Miocene – Oligocene\Miocene
Basal Mid.Miocene
Jimidi Basal Lower Miocene Oligocene\Miocene
Adar Lower-Mid Eocene Early –Mid Eocene
Yale Paleocene Mid Paleocene – Early
Eocene
Unit Late Maastrchtain
Rawat III Lower Campanian- Lower
Unit Maastrichtain (campanian\Masstrichtian
II –Early Maastrichtain
Unit I Campanain or older

2.3.1.1 Unit I
Type section: well AY-1 (3224.8-4544.6 m)
Sandstones (medium- to coarse-grained) with minor claystone interbeds
are the dominant lithology of this unit. The basal part consists of fine-
grained sandstones and minor interbeds of claystones.
Suggested age: Campanian or older (Assemblage Zone I).
Depositional environment: The palynofacies assemblage is
dominated by coarse particles of plant tissues, abundant dark
brown to black degraded debris, and little amorphous material. The
abundant coarse organic matter and the absence of freshwater algae

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suggest deposition under high-energy fluvial conditions (proximal
facies) near the vegetation source.
2.3.1.2 Unit II
Type section: well AY-1 (2268-3224.8 m)
This unit represents a generally coarsening-upward sequence, dominated
by claystones at the base of the unit with minor sandstone intercalations.
The top of the unit consists mainly of medium- to coarsegrained
sandstones.
Suggested age: Campanian/Masstrichtian-Early Maastrichtian (top
Assemblage Zone 1 to base Assemblage Zone III).
Depositional environment: A proximal setting of fluvial system is
inferred from the abundant dark brown to black degraded debris,
the small amount of amorphous material and the absence of
freshwater algae.
2.3.1.3 Unit III
Type section: well AY-1 (1534-2268 m)
Consists mainly of claystones with minor interbeds of fine to medium-
grained sandstones at the base, which merge into claystones with
medium to coarse-grained sandstones interbeds towards the top of the
unit.
Suggested age: Late Maastrichtian (top Assemblage Zone III).
Depositional environment: Palynofacies assemblage is dominated by
coarse particles of dark brown to black degraded debris. The abundant
coarse particles and the absence of freshwater algae suggest deposition
under fluvial conditions near the vegetation source.
2.3.2 Yale Formation
Type and reference section: well AY-2, 1082.6-1531.3 m (RRI &
GRAS, 1991) The Yale Formation is identified in AY-1, AY-3 and AY-
2 wells. Its thickness ranges from 232.3 m in AY-3 to 448.7 m in the
type well (Fig. 6). Lithologically, this unit is composed of interbedded
sand/sandstones and claystones. The sands and sandstones are usually

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light grey or yellowish brown and dominantly medium- to coarse-
grained. They are subangular to subrounded, poorly to moderately
sorted. The claystones are usually light to medium grey and greyish red,
often silty and noncalcareous.
Whereas the lower boundary of Yale Formation coincides with the top
of the Rawat Formation, its upper boundary is highlighted by a change
from a predominantly arenaceous to a more clayey composition typical
of the Adrar Formation.
Suggested age: Mid-Late Paleocene/ Early Eocene (Assemblage Zone
IV/ Assemblage Zone V). Depositional environment: The association of
degraded dark brown to black debris and extremely degraded amorphous
organic matter together with the absence of freshwater algae point
towards deposition under distal facies of a fluvial setting.
2.3.3 Adar Formation
Type and reference section: well AY-1, 765-1095.7 m (RRI & GRAS,
1991)
The formation is identified in the three studied wells in the north of the
Rawat sub basin and range in thickness from 330.7 m in AY-1 to 317.6
m in AY-2 (Fig. 6). The Adar Formation overlies Yale Formation and
underlies Jimidi Formation. It is dominated by light to medium grey and
greyish red claystones locally silty and non-calcareous. Thin interbeds of
greyish brown siltstones and medium to coarse-grained sands often
yellowish brown occur throughout the formation.
The base of the Adar Formation corresponds to the top of the Yale
Formation, marking a shift from a predominantly sand-rich interval to a
more clayey section. The top represents a stratigraphic hiatus where
Early Oligocene and Late Eocene sediments are missing.
Suggested age: Early-Mid Eocene (Assemblage Zone V)
Depositional environment: Palynofacies assemblage noted within
this formation is characterized by abundant degraded amorphous
organic matter with variable amounts of structured and degraded
debris. The presence of some miospores and freshwater algae at the

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base of the formation indicates an onset of lacustrine setting later
shifted to fluvial conditions towards the top of the formation.
2.3.4 Jimidi Formation
Type and reference section: well AY-2, 654.7-765 m (RRI & GRAS,
1991)
The formation is identified in all three wells in the northern Melut Basin
and ranges in thickness from 67 m in AY-3 to 111 m in AY-1, the
section in the type well is 110.3 m thick (Fig. 6).
The Jimidi Formation consists of an interbedded sequence of
approximately equal amounts of sands/sandstones and claystones. Sands
are predominantly medium- to coarse-grained, white, light grey and pale
yellow, whereas sandstones are hard, usually medium-grained, well
sorted with kaolinitic or siliceous cement. Claystones are often light- to
medium-grey and greyish red, locally silty and sandy and non-
calcareous. In AY-2 well, trace amounts of chlorite are noted throughout
the formation. The upper boundary of the formation is depicted on
wireline logs by an increase in gamma ray values, indicating an upward
transition to a sequence rich in claystones assigned to the Miadol
Formation.
Suggested age: Oligocene/ Miocene (Assemblage Zone VI)
Depositional environment: Palynofacies assemblage is dominated by
fern spores, amorphous organic matter with black specks and low
amounts of plant tissues. The presence of scolecodonts, together
with fern spores and freshwater algae, suggests deposition of the Jimidi
Formation in a hyposaline condition during a possible short marine
incursion within a predominantly fluvio/lacustrine setting.
2.3.5 Miadol Formation
Type and reference section: well AY-1, 510.5-654.1 m (RRI & GRAS,
1991)
The Miadol Formation was reported in the three wells in the northern
Rawat sub Basin and ranges in thickness from 175.2 m in AY-3 to 143.6
m thick in the reference well, AY-1 (Fig. 6). Lithologically, this unit

Page | 23
consists predominantly of claystones with occasional thin interbeds of
siltstone and sandstone. The claystone is dominantly light- to dark-grey
and greyish-red in colour. Locally, it becomes very silty and sandy,
grading into siltstone and very fine-grained sandstone. Thin interbeds of
coarse-grained sand/sandstone were seen in AY-3 and AY-2 wells.
The upper boundary of the formation is highlighted on wireline logs by a
marked upward decrease in gamma ray values and sonic interval transit
time. This matches a lithological change from the claystones of the
Miadol Formation to the dominantly arenaceous sequence at the base of
the Daga Formation.
Suggested age: Early Miocene (Assemblage Zone VII)
Depositional environment: Palynofacies assemblage is characterized by
occurrence of some scolecodonts, abundant amorphous organic matter
with black specks, freshwater algae and few plant tissues. The presence
of scolecodonts might indicate a short-time marine incursion in a
predominantly lacustrine setting inferred from the abundance of fern
spores and fresh water algae.
2.3.6 Daga Formation
Type and reference section: well AY-1, 154.0- 510.5 m (RRI & GRAS,
1991)
The formation is identified in the three studied wells in the northern
Rawat sub Basin. Its thicknesses range from 316.5 m in AY-2 to 356.5
m in AY-1 (Fig. 6). The Daga Formation is informally subdivided by
RRI & GRAS (1991) into three units: a lower arenaceous unit, a middle
clay/claystone unit and an upper unit of interbedded clays and sands.
The formation consists of interbedded sands and claystones. The sands
are generally medium to coarse-grained; sub-angular to sub-round. The
claystone is dominantly white to light grey in colour.
The upper boundary of the Daga Formation is marked by an upward
passage into a monotonous sand sequence of the overlying Agor
Formation. The lower boundary of this formation is indicated by a
sudden change from the arenaceous basal section of this formation to a
more clayey interval on the top of Miadol Formation.
Page | 24
Suggested age: Late Miocene-? Pliocene (Assemblage Zone VIII)
Depositional environment: The presence of some fern spores, fresh
water algae and abundant amorphous organic matter at the base of the
formation suggests deposition in lacustrine setting. Towards the top of
the formation, the palynofacies assemblage becomes enriched in coarse-
grained, degraded palynodebris, which may indicate a shift to fluvial
environment.
2.3.7 Agor Formation
Type and reference section: well AY-2, 180.4 m- top not seen (RRI
& GRAS, 1991)
The formation is identified in AY-1 and AY-2 wells in the north of the
Rawat sub Basin with a maximum thickness of ± 180 m in the reference
well, AY-2 (Fig. 6). The thickness of the formation cannot be calculated
since the top of the formation is not identified in any of the studied
wells.
The Agor Formation consists of a predominantly medium- to coarse-
grained, monotonous sand sequence. Its grains are occasionally very
coarse (some pebbles were noted) and dominantly subangular to
subrounded. The base corresponds to thick sand sequence at the bottom
of the formation. Suggested age: Quaternary (based on regional
correlation and stratigraphic position).
Depositional environment: Palynological recovery is generally poor
throughout the Agor Formation. However, lithofacies interpretation
(Bakr, 1995) suggests a fluviatile to lacustrine environment for this unit.
2.3 Stratigraphic subdivisions of the southern Rawat Sub Basin
In 1982 Chevron drilled a single well (code AY-4 in Fig. 6) with a total
depth of 12000 feet (approximately 3657.6 m) in the southern Melut
Basin. Oil and gas shows were reported but not tested and the well was
abandoned (Chevron unpublished report, 1982). Based on well log
interpretation, eight formations were proposed for the subdivision of the
sedimentary sequence in the drilled hole. Correlation of the present
palynological results with the previous dating proposed by RRI &
GRAS (1991) is summarized in Table 2.
Page | 25
In the following sections a brief review regarding the lithostratigraphic
description (RRI & GRAS, 1991), palynostratigraphic and
palaeoenvironmental interpretation (based on the present results) will be
given.

Table 2.2 Previous palyonological datibg versus present work, southern

Melut Basin.
Formation RRI GRAS 1991 Present work
Biyut Neogene – Quaternary Plestocene – Recent
Dulyat Neogene – Quaternary Late Miocene –
Pliocene
Jokau Basal Lower Miocene Oligocene\Miocene
Lau Oligocene Oligocene\Miocene
Sobat Lower-Mid Eocene Early –Mid Eocene
Nasir Upper Paleocene – Eocene Late Paleocene

Nuer Paleocene Late Maastrichtan \

Early Paleocene
Garjak Upper Cretaceous and \ or older Maastrchtain

2.3.1 Garjak Formation

Type and reference section: well AY-4, 2168.7-3657.6m (RRI & GRAS,
1991)
This unit consists of interbedded sandstones and claystones, the latter
show steady upward increase. Sandstones are friable, light-grey and
predominantly fine- to medium-grained, subordinate coarsegrained
sandstone occurs (Fig. 6). Claystones are greyish-red and dark-grey,
micaceous, noncalcareous, locally silty and sandy.

Page | 26
The upper boundary coincides with slight upwards increase in sands and
sandstones content which corresponds to slight increase in sonic interval
transit time.
Suggested age: Late Maastrichtian and older (Assemblage Zone III).
Depositional environment: The palynofacies assemblage is dominated
by black debris few plant tissues and amorphous matter. The presence of
abundant black debris together with miospores and fresh water algae
suggests deposition in a fresh water fluviatile/ lacustrine setting. This
assumption is further supported by lithofacies interpretation (Bakr,
1995).
2.3.2 Nuer Formation
Type and reference section: well AY-4, 1490.5-2168.7m (RRI & GRAS,
1991)
This unit is composed mainly of interbedded sandstones and claystones
and minor intercalations of siltstones (Fig. 6). The sands are
predominantly fine-grained, angular to sub-angular, moderately sorted
with occasional traces of mica and carbonaceous debris. Claystones are
generally blocky, greyish-red and dark-grey, locally sandy and non-
calcareous.
2.4 Tectonic setting:

The major structural features of the Rawat Basin and the surrounding
areas are reviewed in this section and illustrated in Figure 5. A detailed,
illustrated account on the subsurface structure of the southern Sudanese
basins can be found in Schull (1988).

The Rawat and Muglad Basins represent the largest interior rift basins of
Sudan; they appear as a northwestward continuation of the Anza Rift in
Kenya (Fig. 5). In the east-central Sudan, two major basins, mainly the
Khartoum and the Blue Nile Basins, are recognized.

Regional studies (Fairhead, 1988; Bosworth, 1992) relate the initial rift
basin development in central and West Africa to the early break-up
phase of the South Atlantic and the separation of Gondwana during
Page | 27
Jurassic (?)-Early Cretaceous. This incident created extensive shear and
extensional forces, which resulted in a number of graben and half graben
structures in Africa, including in Sudan .

A major fault zone, the Central African Shear Zone (CASZ), appears to
terminate the NW continuation of some of these rift basins. However,
interpretation of gravity data (Ibrahim et al., 1996) suggested the
presence of at least ten sedimentary basins northwest of the CASZ. The
gravity models proposed by Osman (1998) indicate approximately 3000
m thickness of sediments in the Bagbag Basin about 150 km west of
Khartoum .

According to Browne et al. (1985) and Bosworth (1992), the tectonic

evolution of the Sudanese interior rift basins is related to the effects of
Mesozoic-Tertiary movements reactivating the weak lineaments inherent
in the fabric of the Pan-African mobile belts.

The tectonic evolution of the Interior Rift Basins in Sudan can be

divided into a pre-rifting phase, three rifting phases, and a sag phase
(Schull, 1988). The first phase of rifting started in the Late Jurassic (?) to
Early Cretaceous (130-160 Ma) and terminated near the end of the
Albian. The second rifting phase took place during the Turonian to Late
Senonian, accompanied by minor volcanic activity and deposition of
lacustrine, floodplain claystones and siltstones. Andesitic basalt
encountered within the Rawat Formation in well AY-1 dated as
Campanian (RRI & GRAS, 1991) may be related to this phase of rifting.
The end of this phase is marked by the deposition of an increasingly
sand-rich sequence that concluded with the thick Paleocene sandstone
sequence of the Yale Formation. The final rifting phase began in the
Late Eocene to Oligocene. This phase is reflected in the thick sequence
of lacustrine and floodplain claystones and siltstones of the Adar
Formation .Since Mid-Miocene, the area has undergone gentle subsidence with
little or no faulting (Browne et al., 1985).

Page | 28
Fig 2.2 Regional stratigraphic correlation of the phanerozoic strata from
NW sudan to SE Ethiopia via the study area.
Page | 29
Fig 2.3 strctuaral map showing the major rift basins of Sudan and
adjacent Countries ( modified after pudlo et.. 1997)

Page | 30
 CHAPTER THREE

PREPARATION TECHNIQUES AND

METHOD OF STUDY

Page | 31
Cuttings and sidewall core samples were provided by Rawat Petroleum
company. for palynological investigations. The samples were initially
described lithologically before they were subjected to the chemical
treatment. The lithologies are mainly clay stones, shale, siltstones and
sandstones.
3. 1. Techniques
The samples were prepared to extract the palynomorphs and associated
materials using the standard maceration procedures of the Centre for
Palynological Studies Central Petroleum Laboratory This involved pre-
chemical treatment, chemical treatment, post chemical treatment, slide
making and image processing.

Fig 3.1 show ditch cutting sample at 1617 m from the rawat by Rawat
Petroleum Operating CO.

3.2Pre-chemical Treatment
This comprises the cleaning and the crushing of rock samples. Cleaning
The objective here is to ensure that all samples are clean and free from
surface contamination before chemical treatment. Sidewall core samples
were washed under running water and were scrubbed with a clean brush
until all surficial drilling muds were removed. The cleaned samples were

Page | 32
left on sheets of paper towel to dry. The number of each sample was
written on its paper towel to avoid mixing-up the samples. Cutting
samples were washed under running water allowing them to pass
through a 1.70 μm metal sieve to isolate the large pieces which are
probably caved. Five to ten grams of the small cuttings of each sample
were placed in a polythene beaker and washed with water repeatedly
using settling and decanting methods, until supernatant was clear and
they were left to dry for chemical treatment.

Fig 3.2 showing the sample befor Chemical Treatment

3.3Crushing
This applied only to the rock sidewall samples. Two to five grams of
each sample were broken up physically to pea-sized lumps and then
transferred to teflon beakers for chemical treatment. All beakers were
labelled with the numbers and the depths of sample and with (SWC) for
sidewall cores and (CUT) for cutting samples.

Page | 33
 Fig 3.3 showing a beaker made of teflon

3.4 Chemical Treatment

Chemical treatment involved the removal of carbonates, removal of
silicates, oxidation of organic matter and alkali treatment. All chemical
treatments (except alkali treatment) were done in a fume cupboard to
prevent atomising the vapours and releasing them into the laboratory.
3.5 Removal of Carbonates
Carbonates within the sidewall core and cutting samples were removed
by treatment with hydrochloric acid (HCL). 35% HCL was added to
each sample and left for several hours, being stirred occasionally with a
clean glass rod. More acid was added to some samples whenever
necessary to dissolve the remaining carbonates. The contents were then
left until the reaction died out and completed, the excess acid was
decanted. The samples were washed (clean of acid) by water repeatedly
using settling and decanting methods, until they became neutral.

Page | 34
Removal of carbonates was necessary in order to avoid reaction of
calcium with hydrofluoric acid in the next stage, which might lead to the
formation of calcium fluoride gel. It can be only removed by washing in
a boiling hydrochloric acid.
3.6 Removal of Silicates
In order to remove silica, silicates, or metal oxides and to release the
organic material, 40% hydrofluoric acid (HF) was added to each sample.
The samples were left in a fume cupboard for several days, being stirred
twice daily. The time to dissolve the samples in HF varied from 1 to 5
days. Samples with high contents of sand and silt were allowed to stay
longer in the acid, while sample with clay and shale lasted shorter. More
fresh HF was added to the samples with silt and/or sand lithologies to
increase the reaction and dissolve the silicates effectively. After the
digestive disaggregation of the samples and the release of the organic
material, the excess acid was decanted. Each sample was then washed
thoroughly with water in 10 um nylon sieve until the residue was
neutralized. The residue was then divided into two parts, one has been
kept in a small polythene tube labelled (P-HF) which means post HF and
the other half transferred to a 100 ml glass beaker for oxidation.
HF should be handled with great care. The acid's fumes are lethal and
aqueous HF, if spilt on the skin can produce excruciatingly painful and
disfiguring effects (progressive tissue damage that may result in serious
injury and disability) (Phipps & Playford 1984)
3.7 Oxidation of Organic Matter
Oxidation is performed in order to transform at least partially
decomposed organic debris into alkali-soluble "humic acids", thereby
deleting unwanted organic matter and producing ultimately (with alkali
treatment) a palynomorph-rich residue (Phipps & Playford 1984). It is a
delicate, irreversible and crucial step in as much as the palynomorphs
are themselves oxidisable and will be eliminated, along with organic
matter, if they are allowed to stay longer than it should be in an oxidant.
The residue of each sample was first examined under the microscope
and the amount and condition of the organic matter, whether it engulfs

Page | 35
the palynomorphs and the color of the loose palynomorphs were
assessed. Accordingly the appropriate oxidant was chosen. Schulze
solution (KCIO3 + conc. HNO3) was found to be the suitable oxidant
for the samples. The oxidation of the residue in Schulze solution took
time which varied from one sample to another (half to four hours). After
the oxidation was completed, the residue of each sample was neutralised
by washing with water, using 10 um nylon sieve. Each residue was then
examined under the microscope at different stages of oxidation to see if
the best oxidation treatment is reached (usually by applying
KOH to see if the oxidised organic matter was ready to dissolve).
3.8 Alkali Treatment
The alkali treatment was applied in order to dissolve the unwanted,
oxidised organic matter (humic compounds). 2% potassium hydroxide
(KOH) solution was added to the residue of each sample, in 100 ml glass
beaker and left for a few seconds. When the colour of the solution turned
brown, the residue was then washed with water in 10 um nylon sieve,
ready for the next treatment.
Post-chemical Treatment
3.9 Ultrasonic Treatment
Ultrasonic treatment was applied for a few minutes, whenever necessary,
if there were still clumps of organic matter engulfing the palynomorphs,
after the residue was treated by an alkali.

Page | 36
 Fig 3.4 showing Ultrasonic

3.10 Concentration of Palynomorphs

The palynomorphs of each residue were concentrated by applying the
following: Sieving: Large organic particles were removed from the
residue of each sample by sieving, using a clean metal sieve having a
mesh size of 150 μm. Fine particles were removed by washing each
residue thoroughly in 10 um nylon sieve, allowing these fine particles to
pass through it.
Swirling: Small quantities of mineral and/or organic debris were
removed by swirling the residue on 12" watch glass, placed on a stable
surface. The buoyant palynomorphs were gently poured off in a clean
beaker leaving the heavier unwanted particles concentrated mainly in the
lower central part of the watch glass. The process was repeated
whenever necessary if there were still some heavier unwanted particles,
which can be detected by microscopic examination.

Page | 37
Heavy Liquid: Considerable quantities of heavy minerals and/or sand
particles were removed by applying the heavy liquid separation, using
zinc bromide ( ) as a separative medium. Each residue subjected
to this treatment was placed in a clean 50 ml polythene centrifuge tube
and few drops of HCl were added to it, before adding( ), to inhibit
the precipitation of ) ). The contents were then centrifuged at
2200 r.p.m. for about 10 minutes. The floating palynomorphs were
gently pipetted out into a clean beaker using a clean pipette. A few drops
of HCI were added and each residue was washed with water in a 10 μm
nylon sieve until being neutralised.

Fig 3.5 sowing centerfouge used to Concentration of Palynomorph

3.11 Staining of Palynomorphs

The gymnosperm and angiosperm pollen in most of the samples were
found to be pale in colour, which make difficulties in examining or
photographing them. To obtain a good colour and details, staining was
applied. The final cleaned residue of each sample was divided into two
parts, one kept in a clean small polythene tube and labelled, the other

Page | 38
part was stained using "Bismark Brown R". The staining was done in an
alkaline medium to ensure even and permanent staining. Each residue
was washed thoroughly in a 10 μm nylon sieve. Polyvinyl alcohol (1%
solution) was added to each stained residue in a clean small polythene
tube, to inhibit clumping effects and acting as dispersing agent. At this
stage each residue for slide mounting.
3.12 Slide Preparation
was ready Some of the stained residue of each sample was dispersed
evenly and lightly (using clean plastic pipette) on clean cover slips (22 x
32mm, No. 1 grade) placed on a dust protected warm plate and left for
about one hour to dry. A label for each group of cover slips (from one
residue) was placed, to prevent any mix-up. Clean and permanently
labelled slides (by using a diamond tipped pencil) were placed on a pre-
heated hot plate (about 125° F) to warm for a few seconds. Then a drop
of "Petropoxy 154" resin was gently placed on the central portion of
each slide and left for 10 seconds, to get rid of any bubbles which may
have formed in the resin. Each cover slip was angled over the resin on
the slide (the top of the cover slip down) and with the aid of a needle the
cover slip was gently lowered, allowing the resin to flow to all edges of
the cover slip, at the same time avoiding any bubbles to be trapped. The
slides were then left on the hot plate for 15 minutes to dry. Six slides per
each sample were made and labelled, using a paper sticker, showing
depth of the sample and the number of the slide.

Page | 39
 Fig 3.6 showing the Heater

Fig 3.7 Showing the slides after Preparation

Page | 40
3.13 Method of Study and Image Processing
Palynomorph Identification and Counting
All the slides were briefly examined under the microscope to see which
sample has the highest diversity. The slides of the samples having the
highest diversity were examined first, and as many as possible
palynomorphs were identified, before carrying out the counting
Counting has proved to be extremely useful in providing evidence of the
dominant taxa, which may reflect climatic or edaphic changes. The
overall palynomorph representation is affected by the domination of the
highly abundant few species, especially in a very diverse sample. Some
of the samples in this study showed a high diversity and few species
with high abundances. A target of 29 specimens per sample was set for
total count to allow the representation of the very low abundant species.
The remainder of the slides were scanned for the species not included in
the quantitative tally, which were added to the range chart, and not being
included in the quantitative count. Any broken or badly preserved
specimens were excluded from the count. Algae like Scenedesmus and
Botryococcus and reworked material were excluded. Frequency charts
were created to help in identifying the assemblages and associations of
microflora. As
well as statistical graphs for selected species or groups, to aid the
interpretation of the palaeoclimatic environments.
3.14 Image Processing
Selected specimens were chosen for image processing to be presented as
plates. The pictures contained in the plates were sourced using a JVC 3-
CCD colour video camera which was mounted on an Olympus BHT
microscope. Images were previewed using a high resolution Sony PVM-
1444QM colour video monitor. The selected images were captured in
memory before being output (in an array of four or nine) to Sony
UP5250MDP colour video printer. Pairs of the A5 prints produced by
the printer were

Page | 41
 CHAPTER FOURE

MATERIAL AND PALYNOLOGICAL

METHOD

Page | 42
Depth number Palynomorphs Palyndeberice Kerogen tybe
1530 - 1540 spore Plantissus Kerogen type
23 x 150 darkbrown (2)

Spore Plantissus ‫ـــــــــــ‬

23 x 147 brown
Pollen grain Black wood ‫ـــــــــــ‬
23 x 142 remain
Spore Cutical dark ‫ـــــــــــ‬
23 x 143 brown
Spore ‫ـــــــــــ‬
23 x 145
Spore ‫ـــــــــــ‬
23 x 148
Fungal spore ‫ـــــــــــ‬
23 x 144
Spore ‫ـــــــــــ‬
23 x 133
Pollen grain ‫ـــــــــــ‬
23 x 132
Pollen grain ‫ـــــــــــ‬
22 x 126
Spore ‫ـــــــــــ‬
22 x 126
Spore ‫ـــــــــــ‬
22 x 126

Page | 43
 ‫‪Spore‬‬ ‫ـــــــــــ‬
‫‪12 x 124‬‬
‫‪Spore‬‬ ‫ـــــــــــ‬
‫‪11 x 125‬‬
‫‪Spore‬‬ ‫ـــــــــــ‬
‫‪10 x 144‬‬
‫‪Pollen grain‬‬ ‫ـــــــــــ‬
‫‪20 x 125‬‬
‫‪spore‬‬ ‫ـــــــــــ‬

‫‪16 x 151‬‬
‫‪Spore‬‬ ‫ـــــــــــ‬

‫‪201 x 26‬‬
‫‪Pollen grain‬‬ ‫ـــــــــــ‬

‫‪20 x 126‬‬
‫‪Spore‬‬ ‫ـــــــــــ‬

‫‪16 x 128‬‬
‫‪Fungal spore‬‬ ‫ـــــــــــ‬

‫‪12 x 121‬‬
‫‪Spore‬‬ ‫ـــــــــــ‬

‫‪12 x 145‬‬
‫‪Spore‬‬ ‫ـــــــــــ‬

‫‪12 x 131‬‬
‫‪Fungal spore‬‬ ‫ـــــــــــ‬

‫‪20 x 143‬‬
‫)‪Table 4.1 Result of smaple no (1‬‬

‫‪Page | 44‬‬
Depth number Palynomorph Palynodebrice Kerogen type
1660 – 1670 Spore Plantissus dark Kerogen type
3 x 127 brown (2)
Pollen grain Plantissus brown ‫ـــــــــــ‬
4 x 128
Spore Amorphas dark ‫ـــــــــــ‬
4 x 128 brown
Pollen grain Black wood ‫ـــــــــــ‬
3 x 133 remain
Pollen grain Cutical dark ‫ـــــــــــ‬
3 x 133 brown
Spore ‫ـــــــــــ‬
4 x 128
Spore ‫ـــــــــــ‬
4 x 136
Spore ‫ـــــــــــ‬

4 x 140
Spore ‫ـــــــــــ‬
4 x 141
Pollen grain ‫ـــــــــــ‬
7 x 147
Spore ‫ـــــــــــ‬
7 x 131
Pollen grain ‫ـــــــــــ‬
8 x 139
Spore ‫ـــــــــــ‬

Page | 45
 10 x 144
Spore ‫ـــــــــــ‬
10 x 151
Pollen grain ‫ـــــــــــ‬
9 x 145
Pollen grain ‫ـــــــــــ‬
10 x 146
Spore ‫ـــــــــــ‬

12 x 140
Spore ‫ـــــــــــ‬
12 x 134
Pollen grain ‫ـــــــــــ‬
12 x 132
Pollen grain ‫ـــــــــــ‬
13 x 125
Pollen grain ‫ـــــــــــ‬
13 x 134
Spore ‫ـــــــــــ‬
13 x 134
Pollen grain ‫ـــــــــــ‬
13 x 132
Spore ‫ـــــــــــ‬
13 x 131
Table 4.2 Result of smaple no (2)

Page | 46
Depth number palynomorph Palynodeberice Kerogen type
3050 - 3060 Spore Amorphas Kerogen type
23 x 126 d.brown (2)
Pollen grain Amorphas brown ‫ـــــــــــ‬
22 x 126
Fungal spore Plantissus ‫ـــــــــــ‬
22 x 133 d.brown
Pollen grain Plantissus brown ‫ـــــــــــ‬
15 x 137
Pollen grain Cutical d.brown ‫ـــــــــــ‬
15 x 145 Cutical brown
Pollen grain Black wood ‫ـــــــــــ‬
19 x 148 remain
Pollen grain Brown wood ‫ـــــــــــ‬
18 x 138 remain

Pollen grain ‫ـــــــــــ‬

12 x 144
Pollen grain ‫ـــــــــــ‬
5 x 132
Pollen grain ‫ـــــــــــ‬
4 x 140

Table 4.3 Result of smaple No (3)

Page | 47
Depth number Palynomorph palynodebrise Kerogen type

2255-2260 Spore Amorphas dark Kerogen type

23 x 130 brown (2)
Pollen grain Plantissus dark ‫ـــــــــــ‬
20 x 142 brown
Pollen grain Cuticle brown ‫ـــــــــــ‬
19 x 149
Spore Cuticle dark ‫ـــــــــــ‬
19 x 139 brown
Pollen grain ‫ـــــــــــ‬
17 x 148
Pollen grain ‫ـــــــــــ‬
14 x 142
Spore ‫ـــــــــــ‬
12 x 131
Pollen grain ‫ـــــــــــ‬
11 x 145
Spore ‫ـــــــــــ‬
9 x 147
Pollen grain ‫ـــــــــــ‬
4 x 124
Pollen grain ‫ـــــــــــ‬
3 x 139
Table 4.4 Result of smaple no (3)

Page | 48
Depth number palynomorph palynodebrise Kerogen type

2265 - 2270 Pollen grain Kerogen type

9 x 135 (2)
Pollen grain ‫ـــــــــــ‬
9 x 135
Fungal spore ‫ـــــــــــ‬

Table 4.5 Result of smaple no (4)

Depth number Palynomorphs Palynodebrise Kerogen type

4422 - 4422 Pollen graine Planttissus Kerogen type (2)
9x147 (dark brown_)
Sopre Plantissus ( ‫ـــــــــــ‬
1x130 browm)
Pollen graine Black wood ‫ـــــــــــ‬
11x137
Spore Brown wood ‫ـــــــــــ‬
11x138
Pollen graine Amorphas ‫ـــــــــــ‬
11x138 (dark brown)
Pollen graine Cuticale (dark ‫ـــــــــــ‬
11x140 brown)
Pollen graine Cuticale ( ‫ـــــــــــ‬
11x145 browm)
Pollen graine ‫ـــــــــــ‬
11x146
Page | 49
Pollen graine ‫ـــــــــــ‬
11x147
Spore ‫ـــــــــــ‬
11x147
Pollen graine ‫ـــــــــــ‬
Plate(13) No(4)
11x150
Spore ‫ـــــــــــ‬
Plate(14) No(7)
13x155
Spore ‫ـــــــــــ‬
Plate (10) No(3)
13x152
Spore ‫ـــــــــــ‬
Plate (4) No(16)
14x142
Pollen graine ‫ـــــــــــ‬
15x134
Pollen graine ‫ـــــــــــ‬
Plate(12)No(14)
15x137
Pollen graine ‫ـــــــــــ‬
Plate (10)
No(10)
15x140
Pollen graine ‫ـــــــــــ‬
Plate (3)No(8)
15x140
Spore ‫ـــــــــــ‬
Plate
(20)No(13)
17x154

Page | 50
 Pollen graine ‫ـــــــــــ‬
Plate (6) NO(6)
19x128
Pollen graine ‫ـــــــــــ‬
Plate(6) no(5)
21x136
Pollen graine ‫ـــــــــــ‬
Plate(11)
No(23)
21x152
Table 4.6 Result of smaple No (5)

Sample depth Palynomorphs Palynodebrise Kerogen type

Pollen graine Planttissus Kerogen type (2)
20x154 (dark brown_)
Fungal spores Plantissus ( ‫ـــــــــــ‬
25x131 browm)
Pollen graine Black wood ‫ـــــــــــ‬
24x134
Pollen graine Brown wood ‫ـــــــــــ‬
23x128
Pollen graine Amorphas ‫ـــــــــــ‬
23x151 (dark brown)
Fungal Cuticale (dark ‫ـــــــــــ‬
19x137 brown)
Fungal Cuticale ( ‫ـــــــــــ‬
18x132 browm)

Page | 51
Spore ‫ـــــــــــ‬
18x132
Fungal spores ‫ـــــــــــ‬
18x147
Spore ‫ـــــــــــ‬
17x150
Fungal spore ‫ـــــــــــ‬
17x133
Pollen graine ‫ـــــــــــ‬
16x132
Pollen graine ‫ـــــــــــ‬
16x141
Pollen graine ‫ـــــــــــ‬
15x128
Pollen graine ‫ـــــــــــ‬
15x152
Pollen graine ‫ـــــــــــ‬
15X152
Fungal spore ‫ـــــــــــ‬
14x120
Fungal spore ‫ـــــــــــ‬
14x132
Fungal spore ‫ـــــــــــ‬
14x137
Spore ‫ـــــــــــ‬
14x137
Pollen graine ‫ـــــــــــ‬
14x145
Pollen graine ‫ـــــــــــ‬
13x139
Fungal spore ‫ـــــــــــ‬
12x138

Page | 52
 Fungal spore ‫ـــــــــــ‬
11x139
Fungal spore ‫ـــــــــــ‬
10x149
Table 4.7 Result of smaple no (6)

Sample depth Palynomorphs Palynodebrise Kerogen type

3730-3740 m Pollen graine Planttissus Kerogen type (2)
2x120 (dark brown_)
Pollen graine Plantissus ( ‫ـــــــــــ‬
7x121 browm)
Pollen graine Black wood ‫ـــــــــــ‬
15x121
Pollen graine Brown wood ‫ـــــــــــ‬
15x121
Pollen graine Amorphas ‫ـــــــــــ‬
19x121 (dark brown)
Pollen graine Cuticale (dark ‫ـــــــــــ‬
19x120 brown)
Pollen graine Cuticale ( ‫ـــــــــــ‬
3x120 browm)
Pollen graine ‫ـــــــــــ‬
9x144
Spore ‫ـــــــــــ‬
7x145
Table 4.8 Result of smaple no (7)

Page | 53
Sample depth Palynomorphs Palynodebrise Kyrogen type
3360-3370 Pollen graine Planttissus Kerogen type (2)
23x147 (dark brown_)
Pollen graine Plantissus ( ‫ـــــــــــ‬
16x148 browm)
Pollen graine Black wood ‫ـــــــــــ‬
16x145
Pollen graine Brown wood ‫ـــــــــــ‬
9x148
Pollen graine Amorphas ‫ـــــــــــ‬
9x141 (dark brown)
Pollen graine Cuticale (dark ‫ـــــــــــ‬
8x140 brown)
Pollen graine Cuticale ( ‫ـــــــــــ‬
8x127 browm)
Pollen graine Planttissus ‫ـــــــــــ‬
7x129 (dark brown_)
Spore Plantissus ( ‫ـــــــــــ‬
7X150 browm)
Pollen graine Black wood ‫ـــــــــــ‬
7x127
Pollen grane Brown wood ‫ـــــــــــ‬
4x145
Pollen graine Amorphas ‫ـــــــــــ‬
6x153 (dark brown)
Pollen graine Cuticale (dark ‫ـــــــــــ‬
5x144 brown)

Page | 54
 Polen grane Cuticale ( ‫ـــــــــــ‬
4x153 browm)
Table 4.9 Result of smaple no (8)

Depth number Palynomorph Palynodebrise Kerogen type

3360-3370 Pollen grain Amorphas(dark Kerogen type
23 x 135 brown) (2)
Pollen grain Cuticale(dark ‫ـــــــــــ‬
20 x 131 brown)
Pollen grain Plantissus ‫ـــــــــــ‬
20 x148 (brown)
Pollen grain Wood remain ‫ـــــــــــ‬
18 x134 (brown)
Pollen grain Wood remain ‫ـــــــــــ‬
15 x139 (black)
Pollen grain Cuticale(brown) ‫ـــــــــــ‬
10 x1139
Pollen grain Plantissus(dark ‫ـــــــــــ‬
8 x132 brown)
Table 4.10 Result of smaple no (9)

Page | 55
This Fig 4.1 showing samples of spore and pollen grain from
the microscopic study

Page | 56
 CHAPTER FIVE
PALAEOENVIRONMENTAL
INTERPRETATIONS

Page | 57
Sedimentological and palynological criteria were integrated in
deducing the paleoenvironments of deposition of the sedimentary
succession penetrated in all the nine (9) wells provided for study.
The sedimentological criteria included gross lithology, composition,
textural characteristics and Gamma Ray log motifs while the
palynological attributes were occurrences of paleoenvironmentally
significant palynomorphs (e.g. freshwater algae like species of
Pediastrum and Concentricytes, brackish water alga Botryococcus
braunii, marine indices such as dinoflagellate cysts and
microforaminiferal test linings), relative abundance and diversity of
pollen and spores as well as distribution, types and abundance of
palynomacerals.
On the basis of the above criteria, paleoenvironmental inferences for
each of the nine wells are discussed below:
Do Biostratigraphic Studies of Rawat Area

5.1 RAWAT WEST-1 PALEOENVIRONMENTS

The Gamma Ray log provided indicates that the sedimentary
succession penetrated in the Rawat West-1 well over the studied
interval (80 1140m) is composed mainly of claystones with rare
occurrences of thin units of sandstones. The average
sandstone/claystone ratio over the well section is approximately
25:75. The sandstones are, generally, transparent to translucent,
pale yellow, unconsolidated to poorly consolidated, fine to coarse-
grained, sub-rounded to rounded and well sorted. The claystones
are dusky yellow, light olive brown, grayish brown to grayish red,
occasionally medium to light grey and light grey to off white, firm to
moderately hard and sub-blocky to blocky. Carbonaceous detritus
and mica flakes.
The palynofacies assemblages of this well section are, generally,
dominated by pteridophyte spores like species of Laevigatosporites
and Verrucatosporites, Cyathidites minor, as well as few fungal

Page | 58
spores and brackish water alga, Botryococcus braunii. Abundant
Amorphous Organic Matter (AOM), charcoal with black and brown
woody elements constitute the dominant palynodebris contents of
the interval.
The dominance of the gross lithology over this interval by
shales/mudstones (>70%) and the high abundance of Amorphous
Organic Matter (AOM) throughout the interval suggest that low-
energy regimes generally prevailed during the deposition of the
sediment over this interval. The low-energy regimes were only
interrupted occasionally by short-lived moderate to high-energy
bursts when some sands were deposited. In addition, the
palynomorph assemblages and vertical distribution of the various
palynodebris contents suggest a fluvio-lacustrine facies succession
at the Rawat West-1 well. This proposition, combined with
variations in sand/shale ratios, thicknesses of sand bodies, textural
characteristics of sands and Gamma Ray log signatures, has enabled
the Biostratigraphic Studies of Rawat Area
Deductions of deposition environments over the entire studied
interval as follows:
Interval Possible depositional environment of rawatb w-1
(Metre)
49-280 Deep Lacustrine
280-362 Fluvial (overbank/flood plain system)
362-413 Deep Lacustrine
413-475 Shallow Lacustrine/flood plain facies
475-505 Fluvial (meandering channel/overbank complex)
505-562 Shallow Lacustrine/flood plain facies
562-703 Deep Lacustrine
703-734 Shallow Lacustrine/flood plain facies
734-765 Fluvial (meandering channel/overbank complex)

Page | 59
765-828 Shallow Lacustrine/flood plain facies
828-879 Deep Lacustrine
879-923 Fluvial (meandering channel/overbank complex)
923-981 Shallow Lacustrine/flood plain facies
981-1012 Deep Lacustrine
1012-1140 Fluvial(overbank/ flood plain facies)

5.2 MUGUD-1 WELL PALEOENVIRONMENTS

The Gamma Ray log provided shows that the sedimentary
succession penetrated in the Mugud-1 well over the studied interval
(380 1280m) is composed of an upper section (380906m)
dominated by claystones with a low average sandstone/claystone
ratio of approximately 35:65. The lower interval (906 1280m),
however, exhibits thick development of sands/sandstones with only
thin interbeds of claystones. The sandstone/claystone ratio over the
lower interval is approximately 80:20. Although, the
sands/sandstones of the lower interval are generally thicker than
those of the upper interval, they nevertheless share similar textural
and some other physical characteristics. The sandstones are
transparent to translucent, pale yellow, off white, unconsolidated,
occasionally poorly consolidated, dominantly medium to coarse-
grained, occasionally fine and very coarse-grained, dominantly sub-
rounded, occasionally sub-angular and moderately sorted. The
claystones are dark grey to greyish black, greenish grey, dusky
brown, dark reddish brown to moderate brown, light grey,
moderately hard to hard, sub- blocky to blocky and slightly
calcareous to non-calcareous. Trace amounts of mica flakes and
pyrite are occasionally associated with the sediments.
The environmentally significant palynomorphs recorded over the
studied Mugud-1 well section include pteridophyte spores like
Page | 60
Laevigatosporites sp., Verrucatosporites usmensis and Cyathidites
minor with backishwater alga, Botryococcus braunii. Abundant
Amorphous Organic Matter, charcoal with black and brown woods
constitute the dominant palynodebris contents of the well section.
The change-over from a lower section of sand dominance to an
upper section of clay dominance is interpreted to reflect changes in
depositional energy regime from a higher energy regime over the
basal section to a lesser energy regime over the upper part. This
decreasing-upward depositional energy regime is further displayed
in the thicknesses of
Food Biostratigraphic Studies of Rawat Area
VIKING ENERGY
the sand bodies which change from thick amalgamated units over
the lower section to thinner single units over the upper section. In
addition, the palynomorph assemblages and vertical distribution of
the various palynodebris contents suggest a fluvio-lacustrine facies
succession at the Mugud-1 well. This proposition, combined with
variations in sand/shale ratios, thicknesses of sand bodies, textural
characteristics of sands and Gamma Ray log signatures, has enabled
the deductions of depositional environments over the entire studied
interval as follows:
Interval (Metre) Possible Depositional Environment of Mugud-1
380-456 Deep Lacustrine
456-620 Fluvial (meandering channel/overbank
complex)
620-725 Deep Lacustrine
725-800 Shallow Lacustrine
800-866 Deep Lacustrine
866-906 Fluvial (overbank facies)
906-954 Fluvial (meandering channel/overbank

Page | 61
 complex)
954-985 Fluvial (overbank facies)
985-1224 Fluvial (meandering channel/overbank
complex)
1224-1280 Fluvial (Braided channel complex)

5.3 WATEESH-1 WELL PALEOENVIRONMENTS

The available Gamma Ray log indicates that the sedimentary
succession penetrated in the Wateesh-1 well over the studied
interval (230-2990 m) is made up of an upper section (2302346m)
dominated by claystones with a low average sandstone/claystone
ratio of approximately 25:75. The lower interval (2345 2990m),
however, shows frequent alternations of sands/sandstones and
claystones with the sands/sandstones, however,
being more prominent. Over this interval, the sandstone/claystone
ratio is approximately 60:40. Texturally and physically, the
sands/sandstones of this well section show similarity just as the
claystones are similar. The sandstones are, generally, transparent to
translucent, unconsolidated, occasionally poorly consolidated, fine
to medium-grained, occasionally coarse-grained, sub-angular to
rounded and moderately sorted. The claystones are reddish brown,
brownish grey, dark greenish grey to greenish grey, grayish red,
occasionally off white, moderately hard to hard, sub-blocky to
blocky. Carbonaceous detritus, mica flakes and ferruginous stains
are the accessory minerals recorded in this well section.
Abundant Amorphous Organic Matter, common Monoporites
annulatus, Striatopollis catatumbus, fungal spore, charcoal and
woody elements; few fern spores and Botryococcus braunii make up
the significant palynodebris elements recorded over the studied
well section.

Page | 62
The sedimentary column penetrated in the Wateesh-1 well is
interpreted to represent a generally decreasing-upward
depositional energy profile based on the decrease of the average
sandstone/claystone ratio from ~60:40 over the lower section to
~25:75 over the upper section. In addition, the palynomorph
assemblages and vertical distribution of the various palynodebris
contents suggest a fluvio-lacustrine facies succession at the
200 Biostratigraphic Studies of Rawat Area
VIKING ENERGY
Wateesh-1 well. This proposition, combined with variations in
sand/shale ratios, thicknesses of sand bodies, textural
characteristics of sands and Gamma Ray log signatures, has enabled
the deductions of depositional environments over the entire studied
well section as follows:
Interval Possible Depositional Environment of wateesh-1
(Metre)
230-565 Deep Lacustrine
565-754 Fluvial (meandering channel/overbank complex)
754-910 Shallow Lacustrine with shoreface sands
910-1237 Deep Lacustrine
1237-1600 Fluvial (meandering channel/overbank complex)
1600-1757 Shallow Lacustrine with shoreface sands
1757-2140 Deep Lacustrine
2140-2346 Shallow Lacustrine with shoreface sands
2346-2990 Fluvial (meandering channel/overbank complex)

5.4 DURRA-1 WELL PALEOENVIRONMENTS

The studied section (1670 650m) of the Durra-1 well is
predominantly made up of claystones. Significant sandy intervals

Page | 63
are, however, present as indicated by the Gamma Ray log provided.
The average sandstone/claystone ratio over the studied well section
is approximately 30:70. The sandstones are, generally, transparent
to translucent, unconsolidated to poorly consolidated, very fine to
medium-grained, occasionally coarse- grained, sub-angular to
rounded and moderately sorted. The claystones are dark grey,
occasionally dark greenish grey and yellowish red, moderately hard
to hard, sub-blocky to blocky, non-calcareous to slightly calcareous.
Trace amounts of carbonaceous detritus and mica flakes form the
suite of accessory minerals over the section.
Pteridophyte spores especially Cyathidites minor, Verrucatosporites
spp., Laevigatosporites spp.; and abundant Amorphous Organic
Matter (AOM), charcoal with black and brown woody elements,
epidermal cuticles and resin/gelified constitute the palynodebris
assemblage recorded over the well section.
Depositional energy over the studied section of the Durra-1 well is
interpreted to increase marginally from its averagely lowest state
over the lower section (1670 1310m) to a slightly more agitated
state over the upper section (1310 650m). based on
sandstone/shale distribution over the entire section. In addition, the
palynomorph assemblages and vertical distribution of the various
palynodebris contents suggest a fluvio-lacustrine facies succession
at the Durra-1 well. This proposition, combined with variations in
sand/shale ratios, thicknesses of sand bodies, textural
characteristics of sands and Gamma Ray log signatures, has enabled
the deductions of depositional environments over the entire studied
well section as follows:

Interval Possible Depositional Environment of Durra-1

(Metre)
560-960 Shallow Lacustrine with shoreface/deltic sands

Page | 64
 fluvial (flood plain/ overbank facies)
960-1103 Deep Lacustrine
1103-1220 Fluvial (meandering channel/overbank complex)
1220-1489 Shallow Lacustrine with shoreface sands
1489-1670 Deep Lacustrine

5.5 SHAWA-1 WELL PALEOENVIRONMENTS

The Gamma Ray log provided shows that the studied section (905-
450m) of the Shawa- 1 well is made up of approximately 40%
sand/sandstone and +60% claystones. Frequent alternations of
sands and claystones occur over this section with the claystones
being generally thicker. The sandstones are transparent to
translucent, pale yellow,
unconsolidated, occasionally moderately consolidated, dominantly
coarse-grained, occasionally fine to medium-grained, dominantly
sub-angular, occasionally sub-rounded to rounded and moderately
sorted. The claystones are grayish red, medium, occasionally
brownish grey, pale yellow, moderately hard to hard, sub-blocky to
blocky, occasionally silty and slightly calcareous. Mica flakes and
carbonaceous detritus occur over this well section.
The palynofacies assemblage over this interval is dominated by
common pteridophyte spores like Cyathidites minor
Laevigatosporites spp. and Verrucatosporites usmensis; Amorphous
Organic Matter (AOM) with few black and brown wood and
charcoal.
The frequent alternations of sandstones and claystones over the
studied section of the Shawa-1 well, suggests that depositional axis
had frequently shifted during the deposition of this section. In
addition, the palynomorph assemblages and vertical distribution of
the various palynodebris contents suggest a fluvio-lacustrine facies
succession at the Shawa- 1 well. This proposition, combined with
Page | 65
variations in sand/shale ratios, thicknesses of sand bodies, textural
characteristics of sands/sandstones and Gamma Ray log signatures,
has enabled the deductions of depositional environments over the
entire studied interval as follows:
Interval Possible Depositional Environment of Shawa-1
(Metre)
450- Deep Lacustrine
504
504- Fluvial (meandering channel/overbank complex)
643
643- Deep Lacustrine
665
665- Shallow Lacustrine with shoreface/deltaic sands
697
697- Deep Lacustrine
737
737- Shallow Lacustrine/flood plain facies
775
775- Shallow Lacustrine with shoreface/deltaic sands
850
850- Deep Lacustrine
874
874- Fluvial (meandering channel/overbank complex)
905

Page | 66
5.6 TAKA-1 WELL PALEOENVIRONMENTS
The Gamma Ray log shows that the sedimentary succession
penetrated in the Taka-1 well over the studied interval (260 2355m)
is made up of an upper section (260 - 1302m) comprising
alternating sand-dominated intervals and claystone-dominated
intervals and a lower section predominantly composed of claystones
with minor occurrences of thin sand bodies. Over the upper section,
the sandstone/claystone ratio is approximately 45:55 but becomes
5:95 over the lower section. Texturally and physically, the
sands/sandstones of this well section show similarity just as the
claystones are similar. The sandstones are pale reddish brown, light
grey to off white, poorly to moderately consolidated, occasionally
well consolidated, fine to coarse-grained but predominantly
medium to fine- grained, sub-angular to sub-rounded, occasionally
rounded, moderately sorted and occasionally well sorted. The
claystones are reddish brown, light grey to off white, brownish grey,
moderately hard to hard, and sub-blocky to blocky, occasionally
silty, non-calcareous to slightly calcareous. Trace amounts of mica
flakes and pyrite are present over this well section.
The dominant forms recorded over this interval include
pteridophyte spores, Monoporites annulatus, Striatopollis
catatumbus and Botryococcus braunii. Amorphous Organic Matter,
charcoal and black and brown woody elements dominate the
palynodebris assemblage.
The sandstone/claystone ratio which changes from 5:95 over the
lower section to 45:55 over the upper section reflects a more
intense overall energy of deposition over the upper section in
comparison to the lower section which appears to have been laid
down under quiet conditions. In addition, the palynomorph
assemblages and vertical distribution of the various palynodebris
contents suggest a fluvio-lacustrine facies succession at the Taka-1
well. These propositions, combined with variations in sand/shale
ratios,

Page | 67
Po Biostratigraphic Studies of Rawat Area
thicknesses of sand bodies, textural characteristics of sands and
Gamma Ray log signatures, has enabled the delineation of
depositional environments over the entire studied well section as
follows:
Interval Possible Depositional Environment of Taka-1
(Metre)
260-470 Fluvial (meandering channel/overbank complex)
470-577 Deep Lacustrine
577-634 Shallow Lacustrine with shoreface/deltaic sands
634-764 Fluvial (meandering channel/overbank complex)
764-875 Deep Lacustrine
875-1164 Shallow Lacustrine with shoreface/deltaic sands
1164-1240 Fluvial (meandering channel/overbank complex)
1240-1306 Shallow Lacustrine with shoreface/deltaic sands
1306-1500 Deep Lacustrine
1500-1575 Shallow Lacustrine with shoreface/deltaic sands
1575-1853 Deep Lacustrine
1853-2095 Shallow Lacustrine with shoreface/deltaic sands
2095-2355 Deep Lacustrine

5.7 EAST ANGARA-1 WELL PALEOENVIRONMENTS

The Gamma Ray log indicates that the sedimentary column
penetrated in the East Angara-1 well over the studied interval
(1803185m) is predominantly sandy with a sand percentage of
approximately 65%. The claystones which constitute the remaining
35% occur in comparatively thin to moderately thick beds
interlayered with the sands. The claystones, however, become

Page | 68
thicker towards the upper part of the well section. The sandstones
are transparent to translucent, occasionally pale yellowish, light
brown, off white, unconsolidated, occasionally poorly to moderately
consolidated, fine to coarse- grained, occasionally very coarse-
grained, sub-angular to sub-rounded and moderately sorted. The
claystones are light grey to dark grey, brown, greenish grey, firm to
moderately hard, occasionally hard, sub-blocky to blocky and
occasionally silty. Trace amounts of carbonaceous detritus,
ferruginous stains and mica flakes constitute the accessory minerals
suite over this section.
The palynomorphs recorded over this section include Botryococcus
braunii, fungal spore, diatom frustules. The palynofacies contents is
dominated by Amorphous Organic Matter and charcoal with few
woody elements and resin/gelified matter.
The high proportion of sands over this well section suggests that the
depositional energy was high for much of the time during the
deposition of this sedimentary succession. The periods when the
depositional energy waned are represented by the claystones. In
addition, the palynomorph assemblages and vertical distribution of
the various palynodebris contents suggest a fluvio-lacustrine facies
succession at the East Angara-1 well. These propositions, combined
with variations in sand/shale ratios, thicknesses of sand bodies,
textural characteristics of sands and Gamma Ray log signatures, has
enabled the delineation of depositional environments over the
entire studied well section as:
Interval Possible Depositional Environment of east
(Metre) Angara -1
180-320 Deep Lacustrine
320-406 Fluvial (meandering channel/overbank complex)
406-529 Deep Lacustrine
529-730 Fluvial (meandering channel/overbank complex)

Page | 69
730-922 Shallow Lacustrine with shoreface/deltaic sands
922-1223 Fluvial (meandering channel/overbank complex)
1223-1276 Shallow Lacustrine with shoreface/deltaic sands
1276-1982 Fluvial (Braided channel/overbank complex)
1982-2078 Fluvial (overbank facies)
2078-2164 Fluvial (meandering channel/overbank complex)
2164-2245 Deep Lacustrine
2245-2364 Fluvial (meandering channel/overbank complex)
2364-2398 fluvial (flood plain facies)
2398-2496 Fluvial (meandering channel/overbank complex)
2496-2682 Fluvial (Braided channel/overbank complex)
2682-2880 Fluvial (meandering channel/overbank complex)
2880-3185 Fluvial (Braided channel/overbank complex)

Page | 70
CHAPTER SIX
CONCLUTION

Page | 71
1.1 Summary and Conclusion

The study area lies in the Rawat Basin, which is located in the southern part of
the Sudan. The Rawat sub Basin is located north eastward of the Northern
Melut Basin and shares global sedimentary and architectural features. The
Rawat sub Basin shares the common history and lithofacies pattern with the
Northern Melut Basin.

Until now, nothing has been published on the detailed lithostratigraphic

subdivisions of the sedimentary strata in the study area. The present study
focuses on the subsurface facies analysis including sedimentological and
palynological interpretation to characterize the sedimentary facies units,
depositional paleoenvironments and establish aspores/pollen zonation in
Rawat sub Basin.

Eight formations have been identified for the Rawat sub Basin and then
omenclature is the same with those formations of Melut basin. These
formations; from older to younger are Gelhak, Melut, Yabus, Adar,
Jimidi,Miadol, Daga and Agor.

According to electrofacies interpretation of wireline logs the sedimentary

infill of the basin is dominated by fluvial and lacustrine environments.

Lower and Upper Gelhak formations have deposited during Campanian with
itsmaximum thickness recorded closer to the boarder fault. Fluvial
environments were prevailing; ranging from braided to anastomosing
system.An extension occurred during Maastrichtian, the amount of
sedimentation varies from one sub-basin to another; the sedimentary unit
that was formed during this period is referred to as Melut Formation which
deposited in lacustrine to deltaic environment .In the period of Paleocene
there was a break in the deposition (Hiatus) and nothing has been reported
from the entire wells understudy in Rawat sub Basin.The period of Eocene
corresponds to a phase of relative tectonic quietude recorded during this
period which resulted in deposition of Yabus Formation. This formation is
most probably deposited in a According to electrofacies interpretation of
wireline logs the sedimentary infillof the basin is dominated by fluvial and
lacustrine environments.

Page | 72
 Lower and Upper Gelhak formations have deposited during Campanian with
its maximum thickness recorded closer to the boarder fault. Fluvial
environments were prevailing; ranging from braided to anastomosing
system. An extension occurred during Maastrichtian, the amount of
sedimentation varies from one sub-basin to another; the sedimentary unit
that was formed during this period is referred to as Rawat sub Basin
Formation which deposited in lacustrine to deltaic environment. In the period
of Paleocene there was a break in the deposition (Hiatus) and nothing has
been reported from the entire wells understudy in Rawat sub Basin. The
period of Eocene corresponds to a phase of relative tectonic quietude
recorded during this period which resulted in deposition of Yabus Formation
.This formation is most probably deposited in a meander/flood paleo
environment. The maximum extension which occurred during the period of
Oligocene coincided with the deposition of Adar Formation in lacustrine
.Jimidi Formation which is interpreted to be deposited in braided
toanastomosing system marks the beginning of the sag phase. It is followed by
the deposition of Miadol, Daga and Agor formations in fluvio-lacustrine
environments . Lower Gelhak, Upper Gelhak, Melut, Yabus and Adar
formations weredeposited during the syn-rift phase in the period from
Campanian - Oligocene.Jimidi, Miadol, Daga and Agor formations were
deposited during the sag phasein the period from Oligocene - Pliocene. Seven
palynofloral assemblage zones for the interval spanning the LateCretaceous
(Campanian) to Neogene (Miocene/Pliocene) have been proposedfor the
sedimentary units in Rawat sub Basin.

sag phasein the period from Oligocene – Pliocene .Seven palynofloral

assemblage zones for the interval spanning the Late Cretaceous (Campanian)
to Neogene (Miocene/Pliocene) have been proposed for the sedimentary units
in Rawat sub Basin.

Page | 73
 ‫انزُصٍبد‬
‫‪ -1‬تىصيات عامة‬
‫‪ -‬انمطبنجخ ثبنزُعع فً انذساعبد انىفطٍخ‬
‫‪ -‬رذسٌت َرأٌٍم انطالة َانجٍُنُجٍٍه َانمٍىذعٍه انعبمهٍه فً مخزهف لطبعبد انىفظ نضٌبدح‬
‫انمعشفخ َانخجشح‬
‫‪ -‬رُفٍش األجٍضح َانمعذاد انحذٌثخ انمغزخذمخ فً انذساعبد انىفطٍخ َاإلعزكشبف انىفطً‬
‫‪ -‬عمم ششاكخ مع انمؤعغبد راد انصهخ ثمجبالد انىفظ انمخزهفخ نضٌبدح انمعشفخ نهطالة‬
‫َسثظ انجبوت األكبدٌمً ثبنجبوت انعمهً َانزأٌم نغُق انعمم‬
‫‪ -‬رغٍٍم اإلجشاءاد انحكُمٍخ نهجبحثٍه َانمخزصٍه َانطالة مه لجم انُصاسح َفك انجشَركُل‬
‫انمعمُل ثً عبنمٍب نزجبدل انمعهُمبد ‪.‬‬
‫‪ -2‬تىصيات خاصة‬
‫‪ -‬رُفٍش معمم خبص ثعهم انمغزحبثبد انذلٍمخ نزمكٍه انطالة مه انزعشف عهى جمٍع أوُاع‬
‫انمغزحبثبد َمعشفخ انجٍئبد انزشعٍجٍخ انمذٌمخ َاوُاع انكبئىبد انجحشٌخ انزً كبوذ رعٍش فً‬
‫األصمىخ انجٍُنُجٍخ انغبثمخ‬
‫‪ -‬رعٍٍه أعبرزح َمزخصصٍه جذد فً لغم جٍُنُجٍب انجزشَل فً انكهٍخ وغجخ ألٌمٍزً انكجٍشح فً‬
‫عهم انجٍُنُجٍب َثبنكبد ٌفزمش لغم جٍُنُجٍب انجزشَل نهكبدس انجششي فً انكهٍخ‪.‬‬
‫‪ -‬انعمم عهى مشاجعخ َرحذٌث انكُسعبد َإضبفخ كُسعبد جذٌذح فً لغم جٍُنُجٍب انجزشَل‬
‫مثم انجٍُكٍمٍبء انعضٌُخ َعجش اَثبس حزى ٌغزطٍع انطالة مُاكجخ انزطُس فً انصىبعبد‬
‫َانذساعبد انىفطٍخ ‪.‬‬

‫‪Page | 74‬‬
 References

AWAD, M. Z. (1994): Stratigraphic, palynological and

paleoecological studies in the East-Central sudan (Khartoum and
kosti basin), Late Jurassic to Mid_Tertiary .
ESAWI, A.A. (2007): Palynological and paleoenviromental
Interpretation of the late Certaceous to Tertiary strata of the Melut
Basin (southeast sudan). Unpuplished PHD thesis.
P.O.C (2012): Biostratigraphic Study of Rawat Area. Unpuplished
report
E A R (2015): Petroleum Geology and Resources of the Sudan .
HASSAN, M. Z (2016): Sedimentary Facies and Tectono-
Stratigraphy of the late Cretaceous _ Neogene, of Rawat Basin White
Nile State, Sudan. Master thesis .

Page | 75
Page | 76