Fig 1:Outline geological map of the Benue Trough and adjacent areas (after Zaborski, 1998). LBT, Lower Benue Trough; MBT. Middle Benue Trough; UBT Upper Benue Trough. 1. Precambrian. 2. Jurassic “Younger Granites”. 3. Cretaceous.

4. Post-Cretaceous sediments. 5. Cenozoic Recent basalts including those of Cameroon Line.

Journal of Mining and Geology Vol. 47(2) 2011, pp. 147–165 © Nigerian Mining and Geosciences Society (NMGS) - Printed in Nigeria

1116-2775

147

IntroductionCretaceous tectonic evolution and sedimentation along the Benue Trough was not uniform. This has led to the conventional sub-division of the trough into

three parts (Fig. 1). The study area (Gboko area) lies within the Federal Survey of Nigeria 1: 100,000 Gboko Sheet 271, at the extreme northeastern end of

Depositional framework and Cretaceous stratigraphy of the Gboko Area Lower Benue Trough, Nigeria

Tavershima NajimeDepartment of Geology, Ahmadu Bello University, Zaria. Email; tnajime@yahoo.com

Abstract

Detailed geological mapping of the Gboko area in the extreme northern part of the Lower Benue Trough has revealed that the stratigraphy of the area cannot be understood purely on extrapolation from other parts of the Benue Trough. Based on this study, new stratigraphic units ("Akpagher”, “Mayange" and "Ikumbur" formations) are proposed in addition to the Gboko Formation as sub-units of the Asu River Group.

The regressive units overlying the Asu River Group have been sub-divided into the Gbemacha, Nienga and Tse-Agberagba sandstones as sub-units of the previously non-divided "Konshisha Group" of Shell B-P or the presently proposed "Konshisha River Group".

The Ezeaku and Makurdi formations along with the newly named Lessel Sandstone overlie the regressive units. They and the Awgu Formations collectively make up the Cross-River Group.

the Lower Benue Trough, transitional into the Middle Benue Trough (Fig. 2). The area has been given less attention with regards to geological studies than the other parts of the Lower Benue Trough or the Middle Benue Trough. The geology of the Lower Benue Trough has been documented through the tectono-sedimentary studies of Murat (1972), Nwachukwu (1972), Olade (1975) and Agagu and Adighije (1983) and for the Anambra Basin by Agagu et al. (1985) and

Allix (1987). Reyment (1965), Reyment and Mörner (1977) and Zaborski (2000) described the transgressive and regressive cycles related to marine sedimentation in the area. Previous accounts of the stratigraphy of the Lower Benue Trough such as those of Reyment (1965), Murat (1972) Petters and Ekweozor (1982) and Ojoh (1990) (Fig. 3) do not fully account for the local stratigraphic setting of the Gboko area.

Fig. 2:Geological map of the Lower Benue Trough regions and adjoining areas. (after Zaborski, 1998). 1. Cenozoic basalts; 2. Nsukka Formation; 3. Ajali Sandstone; 4. Mamu Formation; 5.

Otobi/Ekeh Sandstone; 6. Enugu Shale; 7. Owelli Sandstone; 8. Afikpo Sandstone; 9. Nkporo Shale; 10, Agbani Sandstone; 11. Awgu Formation; 12. Makurdi Formation; 13. Agala Sandstone; 14.

Amaseri Sandstone; 15. Ezeaku Formation; 16.

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The major geological study covering the Gboko area still remains the work of Shell-BP geologists who produced a map on a scale of 1: 250,000. Other studies with data from parts of the area were by Reyment (1965), Petters (1982), Petters and Ekweozor (1982), Ramanathan and Nair (1984), Nair and Ramanathan (1984), Halidu (1978), Ahmed (1978), Dandume (1978), Adekeye and Akande (2000); (2002) and Adekeye (2003).

The present study has examined the geological setting outcropping basement rocks and the overlying sedimentary rocks of the Gboko area. The study has added new information based on the regional and local

depositional framework and new names for stratigraphic units are proposed.

Sedimentation in the area started with the clastic continental deposits of the Agyaku Sandstone (new name) from Aptian to Middle Albian. Tectonic subsidence and South Atlantic sea-level rise caused the first transgression (mid-Late Albian) when the Gboko Formation, Akpagher Formation (new name), Ikumbur Limestone (new name) and Mayange Limestone (new name) were deposited.

The transgression was followed by a regressive phase (Middle Cenomanian) during which the Gbemacha Sandstone (new name) were deposited in

149

Fig. 3: The Stratigraphy of The Lower Benue Trough region ( After Simpson, 1954; Rayment, 1965; Murat, 1972, Petters and Ekweozor, 1982; and Ojoh, 1990)

the northern part of the area and the Nienga Sandstone (new name) in the southeastern part. The regressive phase was followed by a second transgressive phase (Late Cenomanian to Turonian) when the Ezeaku Formation was deposited in the southwestern part of the area. During the same interval, the Makurdi Formation was deposited in its northern part, the Tse-Agberagba Sandstone (new name) in the mid-southern part and to the east the Lessel Sandstone (new name) was deposited. The third marine transgression in the area (Late Turonian to Coniacian) deposited the Awgu Shale in the western part.

Method of StudyAn aerial photo interpretation of the area was followed by systematic geological mapping on a scale of 1: 50,000. A geological map on the scale of 1: 100,000 was produced and digitized. Traverses were undertaken along water courses and sections were

mapped and logged. Other sections logged were those of hand dug wells, road sections, the quarry section at the Benue Cement quarry near Tse-Kucha and an exploratory borehole near Akpagher.

Surface samples, as well as those obtained from boreholes and roads, rivers and well sections were analyzed by various laboratory methods. Dating of some of the formations were based on stratigraphic positions and the ammonites recovered from some of the sediments.

Depositional Framework And Stratigraphy of The Gboko AreaThe geology of the study area is presented on a scale of 1: 100,000 (Fig. 4). Lithological units in the area were mapped and subdivided into formal stratigraphic units. The stratigraphic succession in the area is shown in Fig. 5 and summarized in Table 1. while lateral and vertical relationships are shown in Fig. 6. These units were correlated with the pre-

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Fig. 5: Generalized stratigraphic subdivisions of the Gboko area in the Lower Benue Trough (This study)

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Fig. 6: Fence diagram showing correlation in the Gboko area

BC: Basement Complex; AK: Agyaku Sandstone; GF: Gboko Formation; AF: Akpagher Formation; KL = Ikumbur Limestone; ML: Mayange Limestone, GS: Gbemacha Sandstone; NS: Nienga

Sandstone; TS = Tse-Agberagba Sandstone; EZ: Ezeaku Formation; MK: Makurdi Formation, LS: Lessel Sandstone and AW: Awgu Formation

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existing regional and local stratigraphy and new names were proposed for those units not previously recognized.

Table 1. LITHOSTRATIGRAPHIC UNITS IN THE GBOKO AREA

Group Formation Classification status of termCross River Awgu Shale OldGroup Lessel Sandstone New

Makurdi Formation OldEzeaku Formation Old

--------------------------------------------------------------------------------------------------------Konshisha River Tse-Agberagba Sandstone NewGroup (modified) Nienga Sandstone New

Gbemacha Sandstone New--------------------------------------------------------------------------------------------------------

Asu Mayange Limestone NewRiver Ikumbur Limestone NewGroup Akpagher Formation New

Gboko Formation Old----------------------------------------------------------------------------------------------

Agyaku Sandstone New---------------------------------------------------------------------------------------------Nigerian Migmatite-gneiss complex OldBasement Complex Older Granites suites Old

Crystalline Basement Rocks (Pre-Cambrian to Cambrian)The outcropping crystalline basement rocks in the Gboko area occupy the east-central part of the study area and comprise a migmatite-gneiss complex, coarse, medium and fine-grained biotite granites and biotite-muscovite granites belonging to the “Older Granites' suites (Falconer, 1911).

Agyaku Sandstone (Basal Unit) (Neocomian to

Middle Albian)

In the Gboko area the name “Agyaku Sandstone” is

proposed for all the clastic sedimentary deposits

directly overlying the basement rocks and ranging in

age from Neocomian to Middle Albian. The type

section of the Agyaku Sandstone is the section exposed

along the Agyaku stream near the Gboko market (Fig.

7). The 8 m thick section consists of fine- grained

sandstones lying below coarse-grained sandstone with

clasts of basement rocks and fine-grained sandstones.

The sandstones outcrop intermittently within Gboko

town with exposed thicknesses varying between 2 and

8 m. Along the Gboko to Akpagher road NE-SW

trending ferruginous sandstone ridges overlying the

basement rocks occur at intervals. The deposits lie in

continuity with micaceous arkosic and micaceous sub-

arkosic sandstones described by Benkhelil et al. (1989)

near Ambigher. These deposits are all part of the

Agyaku Sandstone. The base of the Cretaceous

sediments in most parts of the Lower Benue Trough

has not been observed but the continental arkosic

sandstones seen at the flanks of the basin and in

association with NE-SW faults and graben structures

probably characterize the deposits directly overlying

the basement complex.

ASU River Group

The Asu River Group in the Gboko area comprises the

Gboko Formation and the newly proposed

stratigraphic units of the Akpagher Formation,

Ikumbur Limestone and Mayange Limestone.

Gboko Formation

Reyment (1964) described the limestone deposits

along the Makurdi-Gboko road near Tse-Kucha and

named them the “Gboko Limestone.” Petters (1982)

later described the 80 m - thick quarry section at the

type locality and named it the “Gboko Formation.”

At present the Gboko Formation exposed at the

Benue Cement Company quarry comprises about 120

m (Fig. 8) (Najime et al; 2006) of alternating layers of

limestones, shales and clays. It outcrops over an area 2

of 64 km .

Akpagher Formation

The name “Akpagher Formation” is formally

proposed for limestones, shales and clays exposed

along the banks of the River Kontein and its

tributaries, four kilometers south of Akpagher town. 2

The deposits outcrop over an area of 260 km . The

type section is an exploratory borehole drilled to a

depth of 100 m close to the bank of the River Kontein

(Fig. 9) (the cuttings being kept at the Benue State

Water Board Stores, Makurdi). The deposit overlies

the Agyaku Sandstone though the contact was not

mapped.

Ikumbur Limestone

The name “Ikumbur Limestone” is proposed for

alternating shales/clays and limestones exposed

along a road section about 250 m west of Ikumbur

town close to a bridge along the Gboko-Aliede road. 2The unit is exposed over an area of about 3000 m and

the type section is the road section about 250 m west of

Ikumbur town close to a bridge along the Gboko

Aliede road. The exposure, which is about 10 m thick

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Fig. 7: Type section of Agyaku Sandstone along Agyaku stream south of Gboko 0 0market (N 07 18 .950´ E 08 59.996´)

154

Fi g. 8: Lithostratigraphy of the Gboko Formation at the Benue Cement Quarry

(Type Section) at Tse-Kucha.

Fig. 9: Lithostratigraphy of the Akpagher Formation(exploratory borehole section and Type

Section) near Akpagher

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outcrops on the western limb of an anticline.

The type section (Fig. 10) consists of;

1. 7 m limestones alternating with grey shales;

2. 0.3 m grey shale;

3. 1.2 m dark brownish clay;

4. 1.5 m red clay

Mayange Limestone The name “Mayange Limestone” is proposed for shales and limestones outcropping along a hill beside the River Ategba about one kilometer west of Mayange Village and westward along stream sections of the rivers Ategba and Konshisha. The formation

2has an estimated outcrop area of about 52 km . The 15 m-thick hill section (Fig. 11) beside the River Ategba is designated as the type locality. The hill section consists of weathered blue shales and whitish limestone.Part of the section exposed along the River Ategba beside the hill shows that the Agyaku

0Sandstone, dipping about 60 southwestwards

underlies the shales and limestones of the Mayange Limestone; a similar setting is recorded west of Lobi-Kartyo where a layer of basaltic lava occurs between the Mayange Limestone and the Agyaku Sandstone.

Konshisha River Group

Thick sandstones overlie the Asu River Group in the

southeastern part of the study area and are here

referred to as the Konshisha River Group [=

Konshisha Group of Reyment (1956), (after Shell-B

P)]. According to Reyment (1956), the Konshisha

River Group includes late Albian beds but in part also

corresponds with the Ezeaku Formation. No

subdivisions of this group into formations have

previously been attempted. In the present study, three

distinctive lithostratigraphical units within the group

are distinguished and the names “Nienga

Sandstone”, “Tse-Agberagba Sandstone” and

“Gbemacha Sandstone” are formally proposed for

them. The Nienga and Gbemacha sandstones

represent regressive units deposited from the Late

Albian to Cenomanian in the southern and northern

parts of the Gboko area respectively. The deltaic Tse-

Agberagba Sandstone overlies the Nienga and

Gbemacha sandstones.

Gbemacha SandstoneThe name “Gbemacha Sandstone” is proposed for the regressive facies overlying the Gboko and Akpagher

Fig. 10: The type section of Ikumbur Limestone, 0 0near Ikumbur Town (N7 17.88΄ E8 38.34΄)

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Fig.11: The type section of Mayange Limestone exposed along the River Atebga west of Mayange

0 0(N7 09.65´ E8 56.99´)

formations. The deposits consist of bluish shale, mudstones, siltstones and sandstones outcropping

2over an area of 230 km and with an overall estimated thickness of 1900 m. The deposits are laterally continuous with the lower part of the Makurdi Formation to the north. The type locality is along the River Gbemacha near Gbemacha town. The base of the formation is placed at the topmost limestone layers within the Gboko and Akpagher formations and a thin ferruginous sandstone layer (unconformity) marks the top. The unconformity separates the Gbemacha Sandstone and the Makurdi Formation around Gbemacha.

Nienga SandstoneThe name Nienga Sandstone is proposed for fine to medium-grained sandstones and siltstones alternating with mudstones and shales and unconformably overlying the Mayange Limestone. The type area of this formation is the rivers Ategba and Nienga. The type section is designated at the stream section under the Nienga Bridge (Fig. 12). It consists of well-bedded fine to medium-grained sandstones and dark grey coloured mudstones intercalated with bluish to dark

0 blue friable and fissile shales. The beds dip between 26

0and 45 south to southwest. Exposures of the Nienga Sandstone occur intermittently along the River Nienga up to the confluence with the River Konshisha and continue westward until the unit dips and disappears below the Tse-Agberagba Sandstone. The estimated overall thickness of the deposits is 600 m

2with an outcrop area of about 50 Km .

TSE-Agberagba SandstoneLight to dark grey or brownish fine to medium-grained and thinly to thickly bedded sandstones intercalated with mudstones and clays overlie the Nienga Sandstone. The top of the Nienga Sandstone is marked by the disappearance of the shale/clay alternations with sandstone. Thickly bedded sandstone, which overlies a dark grey shale layer, marks the base of the newly proposed Tse-Agberagba Sandstone. At the Tse-Agberagba Bridge, about 20 m of thinly bedded micaceous sandstones outcrop (Fig. 13). This is designated as the type section. The deposits extend southwards and lie in lateral continuity with the Ezeaku Formation as seen in ex p o s u r e s a l o n g t h e R ive r Ko n s h i s h a . Northwestwards it overlies the Gbemacha Sandstone over a distance of several kilometers along the rivers Nyumula and Gbugbu. Northeastwards it overlies the

157

Fig. 12; The type section of Nienga Sandstone under the Nienga Bridge across River Nienga (N7008.31´

E8054.04´)

Nienga Formation over a distance of several kilometers along the River Konshisha.

The uppermost part of the formation consists of massive sandstones, mudstones and siltstones. Along the River Eochon, clayey sand, mudstones and siltstones capped by laterites overlie thickly bedded sandstones. In the southern part of the area along the River Konshisha, the Tse-Agberagba Sandstone intergrades laterally with shales and limestones belonging to the Ezeaku Formation. The deposits dip predominantly in a southwesterly to westerly direction. A late Cenomanian to Turonian

age is suggested for the formation based on its lateral continuity with the Ezeaku Formation.

Cross River GroupIn the Gboko area, the Ezeaku and Makurdi formations and the proposed “Lessel Sandstone” are included in the Cross River Group.

Ezeaku FormationSimpson (1954) first described the Ezeaku Formation. Its type section (Reyment, 1965), along

10:00N 13:30E

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Fig. 13; The type section of Tse-Agberagba Sandstone exposed immediately west of the Tse-Agberagba bridge

10 0across River Konshisha (N7 04:03 E8 35:02 )

Fig. 14: A section of Ezeaku Formation exposed along the River Konshisha near

Haan 0 0(N7 4.377´ E 8 37.943´)

the Ezeaku River, consists essentially of calcareous shales, micaceous fine to medium- grained friable sandstones and occasional beds of limestone, which may be locally shelly. It passes laterally into the Amaseri Sandstone near Afikpo and the Makurdi Sandstone near Makurdi. Offodile (1976) described the formation in the Lafia-Awe area of the Middle Benue Trough. In the Gboko area, the Ezeaku Formation consists of dark grey fossiliferous limestones intercalated with grey shales and sandstones (Fig. 14). It is exposed along the River Konshisha near Haan and the beds dip steeply westward. The ammonite Wrightoceras wallsi Reyment, 1954 indicates an Early Turonian age for at least this part of the Ezeaku Formation. The limestones are mudstones and wackestones. In the extreme southern part of the area, sections exposed along the River Konshisha consist of thick layers of limestone. The rocks are partially neomorphosed mudstone.

Makurdi Formation

Nwajide and Hoque (1984) and Nwajide (1985)

described the Makurdi Formation as part of the

Ezeaku Formation. It comprises fluvial sandstones

and mudrocks with a middle carbonate-bearing

Wadatta Member. Overall, the formation outcrops 2

over an area of more than 1000 km and has an

estimated maximum thickness of 500 m. In the Gboko

area, the clays and fine to coarse-grained sandstones

overlying the Gbemacha Sandstone belong to the

Makurdi Formation. Eleven kilometers north of

Gboko along the Gboko-Makurdi road, sections with

medium to coarse-grained planar tabular cross-bedded

sandstones underlying clays with a lateritic cap (Fig.

15) belong to the Makurdi Formation. Hill outcrops (5-

10 m-thick) exposed intermittently in the northern and

northwestern parts of the area with ferruginous

micaceous sandstones, clays and laterites as weathered

products of the formation belong to the Makurdi

Formation.

Lessel Sandstone

The name “Lessel Sandstone” is proposed for the

poorly bedded conglomeratic sandstones outcropping

along the River Nienga near Abuul (Fig. 16) and

extending eastward to Lessel Town outside the study

area and southwest-ward to the Ikyobo and Agbeede

areas. The section along the Nienga River shows that

the Lessel Sandstone stratigraphically overlies the

159

Fig. 16:A section of Lessel Sandstone exposed along the River Nienga near Abuul

0 0(N7 06.78´ E8 55.89´)

Fig. 15:A road section of Makurdi Sandstone at 7.8 km north of Tse-Kucha

0 0(N7 28.80´ E8 56.22´)

160

Nienga Sandstone though the contact between the two

formations is not exposed. The sandstones are whitish

around Abuul (Lessel area) and laterally change to

reddish or brownish varieties (ferruginous sandstones)

towards Ikyobo and Agbeede.

AWGU FormationThe Awgu Formation overlies the Makurdi Formation and outcrops to the southwest of Awajir and west of Gungul in the extreme west central part of the Gboko area. The formation consists of bluish to grey shales and siltstones. At the type locality between the towns of Awgu and Ndeaboh in the present Anambra state (Reyment, 1965), the formation consists mainly of marine shales and limestones.

Discussion

The tectono-sedimentary evolution of the area shows

that coarse-grained arkoses, the Agyaku Sandstone,

were generated from source areas and deposited in

subsident areas especially along faulted margins during

the early rift phase from Valanginian to Middle Albian.

Tectonic subsidence and rise of sea-level during the

Middle Albian led to invasion of the South Atlantic

into the Gboko area. From the Middle to Late Albian

the Gboko, Akpagher, Ikumbur and Mayange

formations were deposited marginal to the basement

rocks to the east. From Late Cenomanian to Early Turonian,

Makurdi Formation was deposited in the northern part of the area. In the southeastern part, the Nienga and Tse-Agberagba formations were locally deposited from Late Albian to Early Turonian. In the south and southwestern parts, the sea level rise from Late Cenomanian to Early Turonian gave rise to the deposition of the marine Ezeaku Formation. The Awgu Formation, deposited between the Coniacian and Santonian, overlies part of the Makurdi Formation on the western part of the Gboko area.

The stratigraphy of the Gboko area is reviewed in line with the works of Simpson (1954), Reyment (1965), Murat (1972), Petters and Ekweozor (1982) and Ojoh (1990) and many other workers. An update of these works includes the recognition of the basal units in the areas as a separate stratigraphic unit and the formal name of Agyaku Sandstone is formally proposed. The Asu River Group is also subdivided and new stratigraphic units of the Akpagher Formation, Ikumbur Limestone, and Mayange Limestone are

proposed in addition to the Gboko Formation of Petters (1982). The new units were deposited in different subbasins around the outcropping basement rocks in the area. The name Konshisha River Group is proposed in modification of the “Konshisha Group” of Reyment (1965, after Shell-B P) which has been subdivided into three stratigraphic units with the proposed names of Nienga Sandstone, Tse-Agberagba Sandstone and Gbemacha Sandstone. Another stratigraphic unit was also added to the Cross River Group of Petters and Ekweozor, (1982) and the name Lessel Sandstone is proposed for this new stratigraphic unit.

Conclusion The study of the Gboko area shows that the effects of the tectonic evolution of the Benue Trough as captured along the marginal area of Gboko clearly displays uneven basement topography characteristic of what underlies the sedimentary succession in the Lower Benue Trough. The continental sediments deposited between Neocomian to mid-Albian in the area are thick enough for classification as a stratigraphic unit (Agyaku Formation) as proposed in this study. The deposition of marine sediments from mid-Albian to Early Cenomanian was affected by the underlying topography with the resultant deposition of similar deposits scattered as time equivalents around the basement. The Akpagher, Mayange and Ikumbur stratigraphic units are time equivalents of the Gboko Formation. The regressive Gbemacha and Nienga formations are also time equivalents deposited in different parts of the Gboko area. Between the Gbemacha and Nienga formations, the Tse- Agberagba Formation was deposited in a localized basin as deltaic deposits. The local tectonic setting is also responsible for the age equivalent Makurdi and Lessel formations being deposited in different areas overlying the Gbemacha and Nienga formations respectively during the Late Cenomanian to Turonian transgression. In the southern part the Late Cenomanian to Turonian marine transgression deposition the Ezeaku Formation. The Gboko area was affected by the Late Turonian to Coniacian transgression in the western part when sediments of the Awgu Formation were deposited. The Gboko area presents a setting along the eastern margin of the Benue Trough where tectonic effects related to tectonic evolution of the trough are preserved, to marine and continental deposits can be demarcated and the stratigraphic units can be correlated.

161

AcknowledgementThe frank criticism and contributions of Prof. P.M. Zaborsk are gratefully acknowledged. Shehu Magaji and Christian Okedeh are also gratefully acknowledged for their assistance during field work

and Godwin Amedu for typing the manuscript. The work is supported by the Ahmadu Bello University Senate Research Grant and an AAPG Grain-in-Aid award.

162

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Reyment, R. A. (1964). Review of Nigerian Cretaceous - Cenozoic stratigraphy. Jounal of the Nigerian Mining Geological and Metallurgical Society 1, pp. 61 - 80.

Reyment, R. A. (1965). Aspects of the geology of Nigeria, Ibadan University Press, Ibadan. 154 pp.

Reyment, R. A. and Mörner, N. A. (1977). Cretaceous transgressions and regressions examplied by the South Atlantic. Paleontological Society of Japan, Special Paper 1, pp. 247 261.hell British Petroleum Development Company of Nigeria Limited publication (1957)

Simpson, A. (1954). The Nigerian coalfield: The geology of parts of Onitsha, Owerri and Benue provinces. Geological Survey of Nigeria Bulletin 24. 85 pp.

Zaborski, P. M. (1998). A review of the Cretaceous System in Nigeria. Africa Geoscience Review 5, pp. 3 8 5 -483.

Zaborski, P. M. (2000). The Cretaceous and Paleocene transgressions in Nigeria and Niger. Journal of Mining and Geology 26, pp. 153 - 173

Received 30th March, 2010, Revision accepted 7th June, 2011

164

CORRIGENDUM

JMG Volume 47 No. 1 March 2011, Page 49 with Paper by Obianuju P. Umeji. Palynofacies and

palaeodepositional environment of Campano-Maastrichtian sediments exposed around Leru in Anambra

Basin, southeastern Nigeria, with the following captions should be noted.

Fig. 14. Sporomorphs from Nkporo Shale, Afikpo-4 well

1. Laevigatosporites discordatus Pflug, 1953

2. Laevigatosporites adiscordatus Krutzsch, 1959

3. Psilamonocolpites sp.

4. Polypodaceiosporites lisaticus Krutzsch, 1967

5. Echimonocolpites major Salami, 1985

6. Nigeripollis gemmatus Salami, 1985

7. Tricolporopollenites S.C. I. 141 Jardine and Magloire, 1965

8. Margocolporites vanweiji Germeraad, Hopping and Muller, 1968 X 100

9. Aquilapollenites minimus Jardine and Magloire, 1965

10. Cupanieidites reticularis Belsky, Boltenhagen and Potinie, 1965

11. Margocolporites mandjicus Boltenhagen, 1976

12. Retitricolporites Sp. 1. Lawal and Moullade, 1986

13. Pediculisporis reticularis Belsky, Boltenhagen and Potinie, 196514. Hexaporopollenites emelianovi Boltenhagen, 1967

Fig. 15. Dinoflagellates from Afikpo-4 well

1. Biserial microforaminifer lining

2. Florentinia laciniata Davey and Verdier, 1973

3. Florentinia mantelli Davey and Verdier, 1973

4-6. Xenascus ceratioides (Deflandre, 1937) Lentin and Williams, 1973

8. Apteodinium granulatum Eisenack, 1958

9. Andalousiella polymoypha (Malloy, 1972) Lentin and Williams, 1972

10. Exochosphaeridium striatolatum (Deflandre) Davey, 1969

Fig. 16. More dinoflagellates from Afikpo-4 well

1. Florentinia laciniata Davey and Verdier, 1973

2. Florentinia resex Davey and Verdier, 1976

3. Polysphaeridium subtile Davey and Williams, 1966

4. Florentinia radiculata (Davey and Williams1966) Davey and Verdier, 1973

5. Senegalinium bicavatum Jain and Millipied, 1973 X 400 (dorsal view)

6. Senegalinium bicavatum Jain and Millipied, 1973 X 400 (ventral view)

7 & 8. Andalusiella polymorpha (Malloy, 1972) Lentin and Williams, 1977

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165

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Edited publicationCHUKU, D.U., 1988. Distribution of gold mineralization in the Nigerian basement complex in relation to orogenic

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BookPETTERS, S.W. ,1991. Regional Geology of Africa. Springer-Verleg, Berlin, 722p.Unpublished workKEHINDE-PHILLIPS, O.O., 1991. Compositional variations within lateritic profiles over mafic and ultramafic rock

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Journal of Mining and Geology Volume 47 No. 2 2011

Articles

ANUDU, G.K, OBRIKE, S. E,ONUBA, L. N, AND IKPOKONTE, A. E. Hydro-Geochemical Evaluation of Groundwater Resources From Hand-Dug Wells Around Kakuri And Its Environs, Kaduna State, Northcentral Nigeria pp. 75-85

ANUDU, G.K, ADEKEYE, J.I.D, ESSIEN, B.I AND OBRIKE, S.E. Hydrochemical Investigation of Groundwater Around Sharuwa, Bauchi State, Northcentral Nigeria, pp. 87-95

N. G. OBAJE, A. MOUMOUNI, N. G. GOKI and M. S. CHAANDA. Stratigraphy, Paleogeography and Hydrocarbon Resource Potentials of the Bida Basin in North-Central Nigeria, pp. 97-113

* . SAMUEL B. OLOBANIYI AND ARNO MÜCKE Chemical composition of chromite and

intergrown chlorite in metamorphosed ultramafic rocks (serpentinite and talc schist) of the

Egbe-Isanlu schist belt, southwest Nigeria: genetic implications, pp. 115-134

ONYINYE SHIRLEY ODUNZE AND GORDIAN CHUKS OBI. Sequence Stratigraphic Framework of the Imo Formation in the Southern Benue Trough, pp. 135-145

TAVERSHIMA NAJIME. Depositional framework and Cretaceous stratigraphy of the Gboko Area Lower Benue Trough, Nigeria, pp. 147-163

Scientific editing and composing by the Editorial Assistants, M.E. Nton, T. Najime and O.K. Aromolaron