lithostratigraphic, biostratigraphic, chronostratigraphic analysis of Tanga,Ruvu and Mandawa basin in tanzania

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1. INTRODUCTION
Sedimentary basins are region of prolonged subsidence of the earth’s Surface. In that region there
are accumulation of sediment either actively or inactively. The driving Mechanism of subsidence
are related to the process within earths which are the relatively rigidly, cooled thermal boundary
layer of the earth’s known as Lithosphere. Lithosphere is composed of number of plates which are
in Motion with respect to each other. Sedimentary basins exist as motion of plate tectonics. There
are two type of lithosphere
Continental lithosphere; this is a plate which is able to store elastic stresses over long time
referred as elastic lithosphere. It has strength profile with depth and thin and denser.
Oceanic lithosphere; these are thick and light hence lack low strength layer, its strength increases
with depth to brittle-ductile transition in upper mantle
Relative motion produces deformation, vulcanicity, and seismicity and concentrated along their
boundaries. These boundaries are classified into
 Divergent boundaries mid ocean ridge spreading center of the ocean basin
 Convergent boundaries associated with large amount of shortening such as continental
collision
 Transform boundaries associated with strike-slip deformation
Plate tectonic has the premise that deformation is concentrated along plate boundaries, the
continental lithosphere deform far from plate boundaries and appear to behave at geological time
scale.
Formative mechanism of sedimentary basin fall into small number of categories. These categories
are
 Isostatic consequences of changes in crustal/lithospheric thickness
 Loading of the lithospheres causes a deflection or flexural deformation
 Viscous flow of the mantle causes non- permanent subsidence/uplift

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Tanzanian basin are classified into inland basin, coastal basin, shallow water basin and deep
offshore basin. During the field we conducted coastal basin analysis which categorized into Tanga
basin, Ruvu basin and Mandawa basin. Tanga basin is analyzed from basement, Karoo, Jurassic
and cretaceous and at Ruvu basin we analyzed lithologies from cretaceous and Jurassic and ruvu
river as the boundary between Tanga basin and Ruvu basin. Lastly Mandawa basin which
categorized into groups and formation. Rufiji River as the boundary between Mandawa basin and
Ruvu basin. Coastal basin formed pemian to peasic.
Figure 1. Tanzania Basins
1.2 Location
Coastal basin is the basin which is found at the coastal of Tanzania and it separated by Indian
Ocean an East and metamorphic basement in west. It start from Somalia basin to Ruvuma basin in
south Tanzania. It extends from Tanga region in Northern part and Lindi/Mtwara in southern part
and at central it cross Coast region. Dar es Salaam platform is one of the basin found in Tanzania.

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1.3 Accessibility
Coastal basin is not well accessible by buses but it will be easy to reach the location of outcrop
once land cruiser car is used and in some area it is required to walk in order to reach the place
where outcrop is located. Mostly of the field site can be easily accessed by walk traverse and that
will make to hit the targeted location.
1.4 METHODOLOGY
These are methods involved in our field work in order to gather information during our field route
in all three basins through the equipment’s used to collect data during the basin analysis based on
structure and stratigraphic sequence of surface lithology. The methods that were used during the
field works were;
Data collected through tools such as
 Compass
 GPS and hand lens
 Magnetic compass,
 Geological hummer and sample bags
 Field note book
 Pen and digital camera
Description
 Geological Compass –specifically for structural measurement of strike, dip and dip
direction of the outcrop exposed. Basically, geologists uses geological compass to measure
orientation of geological structures, as they map in the field to analyze (and document) the
geometry of bedding planes, joints and / or metamorphic foliation and lineation. The type
of compass used during mapping was known as Brunton compass and suunto compass.
 Global Positioning System (GPS), for taking coordinate of the area in Universal
Transversal Mercator (UTM) format. Used to know the locality of lithologies in specific
basin
 Geological hammer for splitting and breaking rocks. In field geology, they are used to
obtain a fresh surface of a rock in order to determine its composition, nature, mineralogy,
history and also to estimate of rock strength. Geological hammer also, they are employed

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to break rocks with the aim of revealing fossils inside. Geologist's hammers sometimes
used for scale in a photograph. Fresh surface of a rock from the fields, can be easily
obtained in order to determine its mineralogical composition, nature, and history and field
estimation of the rocks strength. In fossil collecting, and mineral collecting. They are
employed to break rocks with the aim of revealing fossils inside.
 Hydrochloric acid (HCL) for testing the presence of carbonate in a particular lithology’s
 Color pencils, trace papers used for cross section and stratigraphy map construction to
analyses lithologies information
 Field notebook It is of a great significance in the field, we used for booking every piece
of information we came across with along the way. We recorded details about mineralogy,
degree of weathering and specific coordinates of outcrops as well as geological features
like joints, sedimentary structures and so forth.
 Hand lens
 This came into application whenever we wanted to magnify a rock sample for a closer and
precise investigation of mineral composition of the specimens and the true colour.
 Sample bag
 This was used for carrying different rock samples from the field area for the purposes of
doing further analysis or observations of those samples.
 Magnetic pencils
 These were used to taste rocks with iron contents or magnetic properties. Example
Hematite and magnetite
 Marker pens
 Marker pens were used for labeling samples before they are put into the sample bags.
Marker pens were of different colors such as red, blue and black.
 Field camera was used for taking photographs of lithologies and strucuters observed as
well as video clips of all interesting features and outcrops which will be used in the field
report attachment
 Safety clothing were used for ensuring one’s safety or safety involved. They included hard
boots, preferably jeans, helmets, reflectors and safety goggles.
 Tape measure was used during the field for measuring estimation of lithology length and
size

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1.5 Objectives of field study
Objectives of field study in Tanga, Ruvu and Mandawa basin are the following
 To study sequence stratigraphy of coastal basin
 To know the lithologies which are dominant
 To understand petroleum system of coastal basin
 To understand well and enable to differentiate or indicate observable petro physical
parameters
 To analyze the rock lithologies found in term of color, grains size,
 To study the paleontology of coastal basin and its depositions environments

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CHAPTER TWO
2 GEOLOGICAL SETTING OF COASTAL BASIN
Geological setting of coastal basin of Tanzania is associated with tectonic activity. Broadly, the
major features are the northeasterly trending Selous / Ruvu rift basins separated from a north-
south string of embayment collectively termed the Jurassic Rift Basins. A Tertiary sag basin
dominates the offshore Coastal Basin making underlying structure inherited from offshore
extensions of the rift basins. Basin configuration reflects the interaction of structural elements
derived firstly from rifting and secondly from major basement lineaments which fan from
southwest to northwest and may be related to thermal doming in the early Jurassic between
Madagascar and Tanzania.
The main tectonic series which have influenced the structural evolution of the sedimentary basins
of Tanzania are as follows:
 Extensional rifting beginning in the late Carboniferous and extending through the Permo-
Triassic into the early Jurassic.
 Early Jurassic thermal doming between Tanzania and Madagascar leading to enhanced
differential subsidence of the Jurassic Rift Basins on the eastern flank of the Masasi
Basement Spur.
 Bajocian onset of sea-floor spreading in the Somalia Basin along the northern arm of a rift-
rift-transform triple junction resulting in the southward movement of Madagascar along
the transform (Davie Fracture Zone) thereby abandoning the Selous/Ruvu rift as a failed
arm.
 Cessation of sea-floor spreading in the Somalia Basin in the late Cretaceous and
lithospheric cooling causing major subsidence in eastern Tanzania.
 Development of the Modern Rift Basins in the late Tertiary related to a period of major
thermal doming, uplift and erosion in East Africa accompanied by extensional faulting and
subsidence in the offshore area and the formation of the Tertiary sag basin.
The stratigraphic evolution of the sedimentary basins of Tanzania is described below in terms of
four stages in continental rifting, namely pre-rift, syn-rift, transitional and post-rift:

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 Pre-rift Gondwanaland was made up of a series of stable cratonic nuclei separated by
zones of structural weakness later to develop into the rift zones which fragmented the
supercontinent. Basement in the area of the Tanzanian coastal basins comprises high grade
metamorphics, mainly gneisses, of the Mozambique orogenic belt.
 Syn-rift sedimentation began in the late Carboniferous and continued throughout the
Permo-Triassic into the early Jurassic during which time the major Karoo basins rifting
and fault movement initiated erosion and generated fluvial systems which deposited
sequences and fining-upward megacycles of coarse proximal, high and low energy fluvial,
floodplain, deltaic and lacustrine deposits with occasional marine incursions. Each
megacycle corresponds broadly to the Permian and Triassic (Rufiji / Tanga Series).
 Transitional stage during the early Jurassic encompassed the last pulses of major rifting;
it is particularly associated with differential subsidence leading to the formation of a series
of semi-enclosed basins around the flanks of the Masasi Basement Spur and the Dar-es-
Salaam Platform. A widespread transgression resulted in the development of restricted
marine conditions in the subsidizing basins leading to the possible extensive deposition of
evaporites - the Nondwa formation found in the Mandawa basin. On the flanks of the
basins, continental conditions persisted with Lower Jurassic sediments (Ngerengere Beds)
demonstrating similar lithofacies to the underlying megacycles in the Older Karoo,
particularly the widespread distribution of fluvial sandstones.
 Post-rift stage lasted from the Middle Jurassic to the Recent. It began in the Bajocian with
the onset of sea-floor spreading in the Somalia Basin which stranded the Ruvu Selous rift
as a failed arm of a triple junction. This event is marked by a regional unconformity and
the start of a major marine incursion which transgressed a basin topography inherited from
earlier rifting. Renewed conditions of restricted circulation may have resulted in the
widespread accumulation of the Makarawe shale - a potentially good oil-prone source rock.
By the Bathonian, the open marine transgression had reached the boundaries of the rift
basins depositing limestones (Amboni, Kidugallo and Mtumbei) over much of the area.
Callovian extends onwards the coastal basins of Tanzania evolved as a passive continental margin
on a subsiding, northeasterly tilting substratum on which sedimentation was controlled by
intermittent tectonic activity and changes in sea-level. In the deeper parts of Ruvu Basin and Rufiji

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Trough, the mid-Jurassic transgression continued into the late Jurassic depositing argillaceous
sediments of the Bagamoyo formation which forms an effective regional seal in these areas.
Elsewhere, the late Jurassic and early Cretaceous is a regressive phase with the accumulation of
thick continental, deltaic and marginal marine deposits of the predominantly sandy Kipatimu Beds.
A regional mid-Cretaceous unconformity and the deposition of platform carbonates mark the end
of the regressive phase and the onset of a major marine transgression in the late Cretaceous. Local
regressive sedimentation persists in the Cenomanian but generally the Upper Cretaceous comprises
shelf and slope clay stones of the Ruaruke formation. Subsidence continued into the Paleocene in
the coastal and offshore areas, although regression set in as sedimentation rates began to exceed
subsidence and remained until the present. Several phases of uplift occurred in the late Tertiary
resulting in regional unconformities at the base of the Middle Eocene and at the base of the
Miocene. Middle Eocene, Neogene and recent sediments are strongly regressive and comprise
continental, deltaic and marine facies.

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CHAPTER THREE
3.0 Geology and Structures
3.1 Geology
In the field study area we uncounted different lithology’s and structures which indicated that the
basin geology or rock and deformation are differently. Geology of both three basins starting from
Tanga, Ruvu and Mandawa basins are influenced with tectonic activities which lead to formation
of different structures. Mostly dominants rock from the basements are metamorphic rock and at
basins we met with sedimentary rocks.
3.1.2 Lithology
These are observed outcrop/rock from the field site. Those outcrop were firstly described in terms
of name of rocks, grain size, color, hardness, angularity, sphericity, visible porosity, sorting,
carbonate contents and hydrocarbon elements. Through these details the rocks were named
accordingly. The following below are Lithological name as it arranged according to the basins
TANGA BASIN
Mostly dominant lithology in Tanga basin is whitish fine grained dolomitic marble, which reacted
with hydrochloric acid with strike 359 and 021NE at 0494747E, 9495852N at Mbuta quarry at
basement.

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Figure 2. Dolomitic marble of Tanga basement
Sandstone which clastic sedimentary rock which varied in size from fine, medium to course. Some
of those sandstone were calcareous and sand limestone and non-calcareous sandstone. Dominant
minerals are quartz, k-feldspar, mica and iron. Calcareous sandstone found at 0505055E,
9442039N and non-calcareous sandstone found at 0509669E, 9456991N. The difference between
calcareous and non-calcareous is on reactivity or response to hydrochloric acid reaction, calcareous
respond to acid while non calcareous does not. Sand limestone is a sandstone with many sand.
Also there were interbedded layers of mudstone and siltstone and claystones observed.

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Figure 3; Calcareous Sandstone of Lower Karoo
Shale lithology with plant imprints observed at 0489900E, 9450102N which is black in color, hard,
very compacted with hematite, muscovite minerals, poor porosity with finely grained. It is layered
in thin laminated beds with 186 strike 010SE Dip amount. Outcrops was also encountered in
shallow drilled well Kakindu 1 sample.

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Figure 4; Black shale of Kakindu River
Limestone outcrop found in massive layer with fine grained, whitish to grey in color with calcite
mineral, react with hydrochloric acid. Also limestone with different size of grains observed which
termed as oolitic limestone(less than 1 cm) at 0505050E, 9441993N and pizolitic limestone
(greater than 1 cm) at 0504976E, 9442045N with bivalves, echinoids and sponge.

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Figure 5. Limestone of Kiomon Quarry
RUVU BASIN
Gneiss with whitish and black color with foliation is observed at the basement. This lithology
formed a sharp contact with Jurassic sediments at Mkwizu quarry. This metamorphic rock
dominated with hornblende minerals is found at 0429531E, 9296105N and at Kikumbi cha Mkulu
where inferred contact between limestone and gneiss observed windward side
Sandstone which is calcite whitish grey found with course to medium grains. Since contains calcite
minerals it react with hydrochloric acid which is massively and thick bedded at 04118881E,
9249619N with strike 273 and dip 011SE and fine thin layers of sandstone at 0443848E,
9297429N,

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Figure 6; Calcareous sandstone of Kigudalo
Fossiliferous limestone which is grey in color with fine grains is dominant in different location.
Those limestone are massive bedded and some locality are thick with fossils like pectin,
gastropods, echinoids, bivalves and coral at 0418484E, 9267486N. Also oolitic limestone with
many fossil content found at 0426792E, 9284502N and pizolitic limestone at 0411764E,
9249657N. Some layers of mudstone, clay stone and siltstone are found but were not well exposed
at the surface but we observed through drainage and at gullies like at 0433268E, 9265826N

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Figure 7. Fossiferous Limestone of Tonga Hill
MANDAWA BASIN
Chemical sedimentary rock observed at Mandawa basin as gysum, carbonates and salt dome and
Pindilo shale’s which showed salt dispirism due buoyance effect of salt. Pindilo shales are blackish
in color which is very light and found at 0534516E, 8952191N. Gypsum at 0542050E, 8970501N.
This is common in Pindilo group at Nondwa formation

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Figure 8; Pindilo shale of Makangaga Quarry and gypsum
Most limestone is dominated in this basin but the difference between this limestone and limestone
from Tanga, Ruvu basin is in the content of fossils. Fossil content in Mandawa is higher and some
fossils dominated in one location which lead naming rock by using the dominant fossils like
Numulitic limestone at 0552463E, 8973486N and gastropods, sponge fossils present. Coral reef
limestone 0514517E, 9056019N and other limestone like oolites with coral fossils and bioclastic
limestone at 0489470E, 9055729N with strike 201 dip 007. Limestone found at Mandawa group
in Mtumbei formation, Mavuji group in Mitole, Narwehe Kihuluhulu formation

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Figure 9; Nummulitic Limestone with other fossils like bivalves
Ammonitic sandstone found at Mandawa basin with fine to medium grain but yellowish in colour
due to oxidizing environment at 0533434E, 9032093N. Massive and thick bedded sandstone with
fine grains found at 0543393E, 8978992N. Sandstone lithology act as a member in Mtumbei,
Kipatimu, Mitole, Narwehe Kihuruhuru and Nangurukuru formation.
Claystone intercalated at 0493683E, 9057284N with sandstone and observed at contact with
limestone 514311E, 9056227N b.ut this reacted with hydrochloric acid. Fossilized claystone with
belemnites and ammonids which intercalated with sandstone at 0539532E, 8989290N. These
lithologies some intercalated with mudstone, siltstone and claystone. Some interbedded with other
lithologies.
3.2 Structures
Different structures observed within those lithologies. These structures associated with human
activities and others are naturally occurred or we can term those structures as primary structures
and secondary structures. Primary structures are those structures formed during deposition of
sediments while secondary structures are those associated or formed after deposition. These

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structures has got its usual meaning in geology or petroleum geology. We can use those symbols
to know something during our basin analysis. During the field routes we countered a lot of
structures which are the following bellow
Bedding Primary layering in a sedimentary rock, formed during deposition, manifested by changes
in texture, color, and/or composition; may be emphasized in outcrop by the presence of parting
 Bedding plane a distinct surface of contact between two sedimentary rock layers. It
represents mechanical zones of weakness and they form when there is a compositional or
textural difference is exist between two beds. It has been observed in all basins but mostly
in Tanga basin at 0489900E, 9450102N
 Plants imprints these are remains of plant which left on the surface of beds. These are
good indicators of deposition environment and area for hydrocarbon exploration. These
plants imprints are secondary depositional structure. Found at 0490026E, 9450043N
 Joints A fracture in rock along which there has been no displacement. Joints are associated
with tectonic activities and joint may result a fault formation. Fractures are observed in all
three basin due to human and tectonic activities
 Cross beds are surfaces within a bed that are oblique to the overall bounding surfaces of
the bed. Cross beds are observed in all basin especially in Tanga basin at Ndoyo bridge,
kidugalo in Ruvu basin and Ngole in Mandawa Basin
Figure 10; Cross beds

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 Fault is a discrete fracture between blocks of rock that have been displaced relative to each
other, in a direction parallel to the fracture plane.It has been observed at 0431076E,
9297461N
Figure 11; Fault and joints structures
 A fracture or fracture zone in rock along which movement has occurred.
 Burrows the traces of worms or other burrowing organisms that live in unconsolidated
sediment. They stand out because of slight textural and color contrasts with the burrowed
rock.
 Ripple marks Ridges and valleys on the surface of a bed formed as a consequence of fluid
flow. If the current flows back and forth, as along a beach, the ripples are symmetric, but
if they form in a uniformly flowing current, they are asymmetric. The crests of symmetric
ripples tend to be pointed, whereas the troughs tend to be smooth curves. Thus, symmetric
ripples are good facing indicators. Asymmetric ripples are not good facing indicators, but
do provide current directions.
 Graded beds display progressive fining of clast/grain size from the base to the top, and
are a consequence of deposition from turbidity flows.
 Pinch out

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Figure 12; Pinch out structures at River Mringi bridge
 Contact any surface between two geologic units.
 Unconformity If there is an interruption in sedimentation, such that there is a measurable
gap in time between the base of the sedimentary unit and what lies beneath it
 Fold A bend or flexure in a rock unit or series of rock units that has been caused by crustal
movements. Fold structure is encountered at 0534516 E, 8952191N.
Figure 13; one of the observed fold structure

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 Flute casts Asymmetric troughs formed by vortices (mini tornadoes) within the fluid that
dig into the unconsolidated substrate. The troughs are deeper at the upstream end, where
the vortex was stronger. They get shallower and wider at the downstream end, because the
vortex dies out. Flute casts can be used as facing indicators. Found at 0531378 E, 9033810
N

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CHAPTER FOUR
4 STRATIGRAPHY OF EACH BASIN
4.1 TANGA BASIN
Tanga basin has two main boulder faults which are Karoo fault and Cenozoic fault both of which
tend from North East (NE) to South West (SW) where fault divided into two group. Synthetic faul
which lie in the same direction of boulder fault is the one, and the secondly is the ant-synthetic
fault which lies in different direction to the boulder fault. And due to fault then lead to sediments
to be deposited on footwall while some at hangingwall.
Basement composed of dolomitic marble, quarzite, and gneiss at footwall of Karoo that encounter
at Kijenge village where Mbuta abandoned quary found which consist of massive bedded
dolomitic marble of high fracture paraller to bedding plane while other are perpendicular to the
bedding plane of about 10cm to 15cm. Tanga basin mainly based on Karoo age which mainly due
to rifting that pocced upto drift during jurrassic period.
Karoo divided into three part which are lower karoo, middle karoo and upper karoo.
 Lower Karoo consist of coarse to medium grains size and some of fine grain size. At
Umba river there are various litology encounter of coarse grain in texture with some
amount of quartz and soft wall which cuted by water, also boulder which are elongated and
round in shape of yellow brown colour termed as conglomeratic sandstone and arkosic
sandstones that contain feldspar with gneiss boulder. Also in other place there is reddish
brown to dark grey for weathered sample due to iron content as also quartz and feldspar
observed which probabbly carbonecious shale, sandstone, and the interbedded of shale and
sandstone layer
 Middle Karoo start from transition of gradual change in lithology for convolution shape
with some lithic sand which are hard compose of calcite and mud with implits. Middle of
karoo at pangarawe abandoned quarry consist of fissile of fine grained laminated which
are black ion colour with water ring structuers, also cross cutting and paraller cutting beds
are found the lithology was carbonecious shale of moderate to high weathered. For
Kakindu river channel consist of dark gray of fine grain size contain calcite mineral of
strike 140°/ dip 18°/ dip direction 50° (NE) which was shale containing plant imprints, at
0489605E/ 9450319N/ Altitude of 124m.
Upper Karoo divide into lower division of upper and upper division of upper

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 Lower division of upper Karoo is the period when difting occur as intercalated of fine to
medium grain size. At Ndoyo bridge 0511341E/ 9459964N there was fine grain material
to medium with lithic and massive bed of 55° strike05° dip/145° dip direction wich
composed of sandstone bed. At a coordinate 0510761E/ 9459048N there was ripple mark
of fine to medium grain where claystone found inlarger content than sandstone
Figure 14; fine sandstone outcrop
 Upper division of upper Karoo is the one contain very coarse reddish brown colour
sandstone. Near Ngole bridge of 0509454E,9450761N there is arkosic with silica at highly
deformed area which consist of massive sandstone bed, and shale. Also ther was a major
continous fault and rollover truncation
Jurrassic period where the ocean start to open during drifting like Amboni kast as marine
environment contains calcareous in form of limestone which mainly contains oolites and pisiolitic
properties as silica structures with mineals like quartz, calcite and aragonite as light and grey colour
obtained. Ambani bridge is the jurasic where transition from upper karoo as calcareous sandstone
and massiv bedding with some fault due to drifting. For Amboni quarry there is fine to medium
grainsize with some silica contents of massive bedded limestones and at Kimoni lithology found
are mud limestone and limestone.

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Figure 15. ZB limestone
4.2 RUVU BASIN
In ruvu basin drifting is the main process where water overstep Karoo whith maga ccoss bedding.
This basin composed of basement, jurrassic, Karoo, and cretaceous period, where jurassic divided
into three categories which are lower jurrassic, middle jurrassic and upper jurrassic while
cretaceous divided into lower cretaceous and upper cretaceous.
Basement in ruvu basin dominated by gneiss, dolomitic marble, and quarzite which are ductile
materials while basin are of brittle material. Basement make contact with middle jurassic when
overstep karoo at Mkwazu quarry, Kikumbi cha nkuru, and Tonga hills 1,2 and 3.
For jurassic divided into three categories which are lower jurrassic, middle jurrassic and upper
jurrassic
 Lower jurrassic is mainly composed of medium to coarse grain. At kidugalo various
lithology observed like calcareous sandstone, congomeratic sandstone, and siltstone. Also
graded bedded of bed which are of fining upward and of coarse upward. Cross bedding
layer of sandstone found and soft sediment structures which are less compacted of
sandstone with compacted layer which is hard. Oolitic limestone found due to ooids and
cross stratification.

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Figure 16; Oolitic limestone of Kidugalo
 Middle jurrassic mainly composed of sandlimestone, siltstone, and shale as at Msolwa
quarry where there is quartz, mafic grains, calcite, and feldspar with bedded layer of about
. Also coraliferrous limestone and bilvalvia as fossilferous limestone observed as the grain
size of the rocks ranged from fine to medium size. As the middle jurassic overlay the
Basement.
 Upper jurasic is mainly composed of marine environments. At Pera there is intercaleted
between upper jurasic and lower cretaceous, where the grainsize are of fine which are light
brown of calcite, illite and smertite mineral. Also mainly place of upper jurasic composed
of coral species, bilvalvia as imprints and boulder of siltstone between claystone, so the
litology are calcareous siltstone and calcareous claystone
And cretaceous divided into two parts which are lower cretaceous and upper cretaceous.
 Lower cretaceous is the period where regration took place as it compose of medium to
coarse grain size. In Mwetemo abandoned quarry composed of red, light, brown, yellow
and black coroul while quartz and feldspar observed and lithology obtained are
congomeratic sandstone.
 Upper cretaceous is of the transgration period composed of fine to medium grain size at
region scale. At pera abandoned quarry where light green, and redishbrown to pink/red??
colour and minerals like feldspar, k-feldspar, and calcite as it fizz when reacting with

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hydrochloric acid, and lithology observed are calcareous siltstone, calcareous sandstone,
siltstones and mudstone.
4.3 MANDAWA BASIN
It has been classifield into groups and formation. There are five groups such as
PINDIRO GROUP
Oldest group with one observed formation which is Nondwa formation which dominated with
evaporates. It has been formed during triasic and comprises Claystone, gypsum, carbonates and
salt and black shales termed as Pindilo Shales. Salt diapirism occured due to bouyance effect
MANDAWA GROUP
It has three observed formation with different members in each formation. These formation are the
following
Mtumbei formation it is formed during mid jurasic and has limestone member which varies from
down with oolitic limestone and up with bioclastic limestone and sand limestone with calcite
minerals. It is fine grained limestone which fizzy when reacted with greyish in color.sand
limestone also reacted with hydrocloric acid
Kipatimu formation is the formation formed during upper Jurassic with two members such as
lower kipatimu with fine grained sandstone and intercalation of claystone. And at upper kipatimu
with course grained sandstone, claystone and kaolinite.
MAVUJI GROUP
Mitole formation it is upper crateous kimedian to belycian with two members. Lower Mitole has
oolitic limestone with fossils such as bivalves and Upper Mitole is dominated with sandstone
lithology which is finely grained
Nalwehe formation dominated with limeston on top or at lower elevation and sanstone lithology
at upper height. Both has fossil contents such as corals and bivalves.
Kihuluhulu formation is formation with dominant reef limestone, calcareous limestone and fine
grained sanstone with some fossils such as ammonites, belemnites.
KILWA GROUP
Nangurukuru formation is the formation formed during santonian to missipian at Upper
crateceous dominated with fine greyish claystone which is bloke and calcareous and some
calcareous sandstone and structures like flute carst, joints and fossils. Also limmonitic yellowish

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sandstone observed and it is yellow in color due to environment depostion wwhich led to iron
presence. Neretic erchno facies used to distringuish Nangurukuru claystone and Kivinje claystone.
Kivinje formation it is dominated with fine grained greyish claystone which is covered with
mudstone on top of it. It does not react with hydrochloric acid and is highly tectonically desturbed.
In geological time scale is found formed during paleocene to lower miocene
Masoko Formation it is mid eocene formation with whitish nummulitic limestone which react
with acid. Found to have many fossils like corals, bivalves, gastropods and Nummulites thats why
it is termed as nummulitic limestone

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CHAPTER FIVE
5.0 PETROLEUM SYSTEM RELATION TO BASIN
Petroleum systerm it compises reservoir, seal( cap rock), source rock, trap as the elements of
sedimentary basin. The process involved are maturation and migration that related to events about
space for accomodation and timing in case of geological time.
 The source rock should compose organic matter in the shale or limestone.
 The reservoir rock must be porous enough for hydrocarbon to be preserved which is due to
diagnesis for primary porosity while secondary porosity due to chemical reaction example
 sandstone. Also reservoir must be permeable enough. But for the case of claystone have
high porosity but no interconected pore while sandstone have low porosity but high
interconected pores because of the way sediments compacted.
 Migration of hdrocarbon is the process of oil/gas to shift from one place to another which
can be primary migration as the hydrocarbon from the source to the reservoir and secondary
migration is about from the resrvoir to the caprock. The good caprock can be salt and
anhydrite/claystone due to more plastic formation.
 Trap is the element which can be of structure, stratigraphic or combination. As structural
trap is due to tectonic activities example fold to make anticline, and fault for deposition.
While stratigraphic is about cyncline like salt domes.
5.1 Tanga basin
In Tanga basin the source rock found at middle karoo where at Kakindu River composed of shale
which contain plants remain. The reservoir due to migration can be at lower division of upper
karoo which consist of sandstones while cap rock can be at upper division of upper karoo, and the
seal can be jurasic period at Amboni which consist limestone.
5.2 Ruvu basin
For Ruvu basin the source rock can be at middle jurasic which compose of most of fossils, the
reservoir rock can be lower cretaceous due to composition of medium to coarse grain size while
trap can be at upper cretaceous.
5.3 Mandawa basin

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Since Mandawa basin is dominated with sandstone, limestone and intercalation of mudstone and
clay stone it is very potential in hydrocarbon exploration due to being a good source rock and good
reservoir. Also there are many fossils content in different formation like Mtumbei, Mitole,
Kihuruhulu and Nangurukuru formation.
On comparison of those basin Mandawa basin seem to be potential because there are some drilled
exploration well which shows high percentage of hydrocarbon richness and some formation
characters relates for example Songosongo relates to Mtumbei. Tanga basin is very potential due
to observed lithology characters such as porosity, permeability and source rock and reservoir rock.
Ruvu basin follows and does not have much fossils content as Mandawa or Tanga basins
5.4 Paleontology
Is the study of remains of living things such as plants and animals who lived in ancient time. These
fossils become deposited when sediments deposits of after the sediments become deposited. In
petroleum it can be used to study the area and correlate to petroleum system. During the field work
we counted a lot of fossils in all basin but its content differs. Such countered fossils are important
for deposition environment, direction of fossils, maturity of hydrocarbon, indication of reservoir,
age of the rock, dominant fossils presents. Mostly fossils found in Tanga basin are plant imprints
on a shale which used to indicates as fluvial deposition environment, coals, gastropods, Bivalves,
burrows, pizolite and oolites and at Ruvu basin are coal, gastropods, Bivalves, belemnites, corals,
pectens, and at Mandawa basin the same fossils observed but others found fossils are nummulitesa
t 0552463E, 8973486N ammonites, reef corals, skoliptus and thallathinoids, trace fossils and
neretic facies at 0531378E, 9033810N.

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CHAPTER SIX
FIELD EXECUTION AND RECOMMENDATION
6.1 Field execution
There are shallow bore which were drilled by TPDC and others are in process of drilling. So we
visited there for more study and explanation about stratigraphic of the drilled well and the aim of
the drilling. Their main aim is to know the karoo beds stratigraphy in order to correlate and to test
source rock. Drilling operation was done by STAMICO and the sample which obtained were
analyzed preliminarily and then properly packed and sent to Dar es salaam where they stored and
other analyzed in the Laboratry.
6.2 Recommendation
Basin analysis and sequence stratigraphy field is very interesting and enjoyable field for the
students who took petroleum because it bring understanding of mostly basin lithologies and
structures and leaves them with many question which will them to do their final year research or a
scientific research about basin and hydrocarbon potentiality. Also it bring the students awareness
about deposition information and petroleum system in general. But this field has some difficulties
to accomplish it effectively and when it will be once again conducted needs some improvements.
These are
 Transport facilities such will have the student to reach all desired localities
 Increase number of equipment so that it will be easy to study many things for example
magnetometer and gravimeter
 Communication or information should be sent early as possible to the local administrative
 Enough fund or finance to the students which will help them to do field work effectively
 Lastly more expose to other related basin like Ruvuma basin, Malagalasi basin so that they
can observe the difference which exist and make other basin to be more potential and other
not

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CHAPTER SEVEN
7.0 CONCLUSION
Coastal basins are result of tectonic activity which lead to rock fragmentation due to rifting and
drifting extension. The sediments become deposited at the low land area through water bodies like
fluvial during Karoo rifting, marine during Jurassic and transition and terrestrial. These lead to
formation of clastic, bioclastic and chemical sedimentary rock. Metamorphic rock acted the source
of sediments in coastal basins. Observed lithologies are good source rock and reservoir and their
petrophyisical parameters are indication of good location for oil and gas investigation, also fossils
which are seen like bivalves, gastropods, sponge, reef coral, are the good indicators. These gives
an evidence and and attraction for more detailed investigation of oil and gas
Field work based on investigation and observation of surface outcrop were conducted from Tanga basin in
north upto ruvu basin and Mandawa basin. Exposure are along quarry, roads, rairway cut, river stream
which based on lithological and paleontological differences where by tectonic and stratigraphical frame
work obtained.