Paleobiogeography and Depositional Environment of ...

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ISSN 0974-5904, Volume 07, No. 03

June 2014, P.P.808-815

Paleobiogeography and Depositional Environment of the Maastrichtian-Late Paleocene Dange Shale, Sokoto Basin, NW Nigeria TOYIN A1, AYINLA H.A2, ADEKEYE O.A2 AND BALE R.B 2 1

Federal University Lokoja, Lokoja, Nigeria 2 University of Ilorin, Ilorin, Nigeria Email: [email protected]

Abstract: Illela borehole in the Sokoto Basin has a total depth of 100.7m with three distinct lithologies; 36.30m thick calcareous and variably coloured greyish-dark shale of Dange Formation, succeeded by a 31.44m thick limestones of Kalambaina Formation with 1.7m thick shaly limestones inclusive. The uppermost part of the section belongs to the Gwandu Formation which consists of intercalation of silty-clay, muddy-siltstones and well lithified ironstone. The borehole section is delineated into upper foraminifera and lower ostracod biostratigraphic units as no formal biostratigraphic zonation could be attempted due to low diversity of both benthic foraminifera, marine ostracods and the absence of planktonic foraminifera. The similarity of the ostracod assemblages between North Africa (Libya), Iullemeden Basin (Illela borehole, NW Nigeria, Mali and Niger Republic) and South-Western Nigeria suggests that a marine connection exists between the Gulf of Guinea and the Sokoto Basin via the area occupied by the River Niger during the Paleocene. Keywords: Illela, Gada village, Paleobiogeography, Benthic foraminifera, Ostracods. 1.

Introduction:

Detailed paleoecological interpretation of past environments with regard to paleobathymetry, paleosalinity or paleo-oxygenation is discussed with the aid of foraminifera. (Sliter & Baker, 1972; Murray, 1991). The interpretation is based on comparisons with modern environments and their faunas. Marine Maastrichtian and Paleocene outcrop in north-western Nigeria, mark the south-eastern limits of a major West African intracontinental basin, the Iullemmeden Basin. This basin was occupied by an embayment of the Tethys Sea during the Maastrichtian and Paleocene age, whereas the foraminifera of the Paleocene deposits of the Iullemmeden basin belong to the Tethys paleobiogeographic provenance (Berggren 1974; Petters 1978a). The dissimilarity between the Maastrichtian microfaunas of north-western Nigeria, and the pinch-out of marine Maastrichtian tethyan embayment did not extend southward beyond north-western Nigeria (Petters, 1977). 1.1. Geologic setting of the Sokoto Basin: The Cretaceous sediments in the Sokoto Basin consists of two parts; the basal is the lower clastic succession representing the ‘’Continental intercalaire” of Kogbe (1981) which is considered to be late Jurassic to early

Fig1: Geological map showing some Formations of the Sokoto Basin, North-western Nigeria Cretaceous in age, this is marked by the Illo and the Gundumi Formations overlying the Precambrian basement rocks (table1).

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T OYIN A, AYINLA H.A, ADEKEYE O.A AND B ALE R.B

809

Table1: Geological sequence in the North-western Nigeria sedimentary basin (Kogbe, 1979) Age

Formation

Quaternary

Sandy grits, laterite

Eocene-Miocene

Gwandu Formation Unconformity Gamba Formation Kalambaina Formation Dange Formation

Upper Paleocene Maastrichtian Lowermost Cretaceous or Older

Precambrian

Unconformity Wurno formation Dukamaje Formation Taloka Formation Unconformity Illo & Gundumi Formation Major unconformity Basement complex

The second phase of deposition began during the Maastrichtian when the Rima Group was deposited unconformably on the pre Maastritchtian continental beds, the Taloka Formation is basal part of Rima Group and comprises white, fine grained, friable sandstones and siltstones with thin intercalated mudstones and carbonaceous mudstones or shales. A poorly preserved mollusc along with bioturbated horizons, flaser bedding and palaeosols was recorded in this formation. (Jones, 1948; Kogbe, 1981) The Dukamaje Formation predominantly consists of shales with limestones and mudstones; its basal and upper parts are made up of shales while the middle part consists of limestones, marls, yellow clays and shales. A ferruginized gypsum bearing bone-bed with a diverse fauna of fish, turtles, crocodiles and mosassaurs mark the basal part of this formation. The uppermost part of this group is the Wurno Formation which consists of friable fine grained sandstones with intercalated siltstones and mudstones. An unconformity separates the Rima Group from the overlying late Paleocene Sokoto Group (Petters, 1979a; Kogbe, 1981; Reyment, 1981) and this break marks an interval of weathering and erosion. The Dange Formation is the basal unit of this group, consists of slightly indurated bluish greyish shale interbedded with thin layers of yellowish limestone. The shale includes bands of fibrous gypsum with numerous irregular phosphatic nodules which were probably derived from the abundant fossil vertebrate remains present in the formation. The Kalambaina Formation consists of a 12m-20m thick marine, white, clayey limestones and

Group ---

Environments Continental

‘’Continental terminal’’

Continental

Sokoto group

Marine Brackish water with brief intercalation

Rima group ‘’Continental intercalaire’’

Continental

shales rich in invertebrate fossils, mainly echinoids, corals, nautiloids, gastropods, foraminifera and ostracods (Reyment, 1965; Petters, 1978a).The Gamba Formation is the topmost unit of this Sokoto Group consists of greyish laminated shales which are folded due to removal by solution of the underlying limestones and the slumping of the underlying beds. Sedimentation in this basin terminates with the deposition of Gwandu Formation which comprises red and mottled massive clays with sandstone intercalation. Continental origin has been assigned to these sediments as well as EoceneMiocene age from palynological data (Kogbe & Sowunmi, 1974). 1.2. Materials and Methods: Twenty three drill core samples of shales, shaly limestones and limestones of the Dange and Kalambaina Formations penetrated by Illela borehole of the Nigerian Geological Survey Agency were selected at 5m intervals. The depth of the borehole is 100.7m with three distinct lithologies; 36.30m thick calcareous and variably coloured greyish-dark shale of Dange Formation, succeeded by a 31.44m thick limestones of Kalambaina Formation with 1.7m thick shaly limestones inclusive. The uppermost part of the section belongs to the Gwandu Formation which consists of intercalation of silty-clay, muddy-siltstones and well lithified ironstone. In addition to this, further six fossiliferous shale samples from Dange Formation exposed at Gada village (N130 491 50 751E) were also selected to complement the core samples.

International Journal of Earth Sciences and Engineering ISSN 0974-5904, Vol. 07, No. 03, June, 2014, pp. 808-815

Paleobiogeography and Depositional Environment of the Maastrichtian-Late Paleocene Dange Shale, Sokoto Basin, NW Nigeria

G A

E FO

RM

IO AT

N

CK HI T

N

S ES

) (M TH LI

O

LO

GY

E PL R M BE A M S U N

DESCRIPTION

Lateritic Overburden

12 GA 9 11 GA 8 10

GA 7

9

DU KA M AJ E

Light, grey, Carbonaceous gypsiferous, phosphatic and fossiliferous shale

8 GA 5 7

GA 4 6

5

GA 3

4

3

GA 2

GA 1B

TA LO K A

M A A S T R IC H T IA N

GA 6

White, Friable & Massive Siltstone with Subrounded Clayball Key

2 GA 1A

1

Gypsiferous fossiliferous shale Siltstone with clay balls

Scale: 2cm =1m 0

Fig2: Lithostratigraphic section at Gada village (N130 491 50 751E)


810


811

MB Fig3: Gastropod (G) shell implaced within Dukaje shale at Gada village

The samples were digested and washed in order to obtain the microfossil species for study. About 100150g of each sample was broken into smaller sizes by hand and the broken samples were put into various well labelled plastic containers and digested with 10% hydrogen peroxide solution. This was left for about 24hours to ensure complete digestion. The digested samples were washed using 0.063mm mesh sieve size using running water. The residues were air dried and stored carefully in a well labelled cylindrical plastic container. Picking, identification and description of the foraminifera and ostracods species was carried out under a binocular microscope. 1.2.1. Microfossil distribution: The microfossils observed in the present study are essentially benthic foraminifera and ostracod and no planktonic foraminifera were observed. The few available benthic foraminifera species in the Dange shale sediments penetrated by Illela borehole and those at Gada village include; Lenticulina sp, Planulina sp, Haplophragmoides sp, Elphidiella africana, Cibicides praccursorious, Gavellinella lellingensis (Plate1).

Fig4: Mammalian bone (MB) exposed along GadaKaffa road

Lenticulina sp

Planulina sp

Cibicides praccursorious

Gavelinella lellingensis

Ephidiella africana

Ephidium oceanensis

Plate1: Foraminifera species in the late Paleocene Dange shale and Kalambaina limestone Formations, Illela borehole and Gada village International Journal of Earth Sciences and Engineering ISSN 0974-5904, Vol. 07, No. 03, June, 2014, pp. 808-815

Paleobiogeography and Depositional Environment of the Maastrichtian-Late Paleocene Dange Shale, Sokoto Basin, NW Nigeria The ostracods species include; Actinocythereis asanmamoi Reyment, Iorubaella ologuni Reyment, Krithe Kalambainensis Reyment, Nucleolina tatteulensis (Apostalescu), Bairdia ilaroensis Reyment, and Buntonia Beninensis Reyment. Few of the available benthic foraminifera and ostracod microfaunal assemblages recorded in this study were also recorded by Kogbe, 1979 at DangeKalambaina section from Gada village. The low diversity of both benthic foraminifera assemblages and the marine ostracods in the studied sediments coupled with the absence of planktonic foraminifera make it difficult to attempt formal biostratigraphic zonation. However, it is possible to delineate the borehole section into upper foraminifera biostratigraphic unit and lower ostracod biostratigraphic unit (Table 2) In addition to these afore-mentioned microfaunas, gastropod shells also observed during the field work exercise along with vertebrate fossil remains especially at an abandoned quarry site along Gada-Kaffa road. The fossils include; fish remains, fragments of mammalian bones, and teeth (Figs. 3 & 4). 1.2.2. Paleoecology of the Benthic Foraminifera: Haplophragmoides sp: This is an infaunal genus and is commonly found in mud-sand substrates especially in the marine zones ranging from marsh hypo saline lagoons and estuaries to bathyal. (Murray 1991; Bronnimann et al., 1992; Adekeye 2003). Elphidiella Africana: It is an infauna, free detritivore living in sand substrates and they basically dwell in cold region especially at the inner shelf (Murray, 1991). Cibicides sp: It is an epifaunal, passive suspension feeder (Murray, 1991) that lives on hard substrates. It dwells in cold-warm environments and is a marine

Actinocythereis Asanmamoi Reyment

Iorubaella Ologuni Reyment

812

genus. It lives in lagoons, shelf-bathyal regions and is found at a depth > 2000m. Gavellinella sp: This is epifaunal and a marine genus that lives in hard substrates. It is essentially a passive suspension feeder, living in a temperate-cold area at the shelf-bathyal regions (Murray, 1991). This genesis may also be allocated to dysoxic environments. Planulina sp: This is an epifaunal and are passive suspension feeders living in marine environments at the shelf –bathyal regions. It may also be allocated to dysoxic environments. Lenticulina sp: This is also an epifaunal, free living genus that lives in mud substrates. It is also a detritivore living in cold regions, and mostly found in outershelf and bathyal regions. 1.2.3. Paleobiogeography and paleogeography of the ostracods: Majority of the ostracods species observed here have a wide geographic distribution in West and North Africa. They are represented in Mali, Libya, Niger Republic and Coastal Nigeria. (Kogbe et al., 1976) These assemblages have a transitional status between the Paleocene assemblages of North and West Africa. The documentation of the geographic distribution of the ostracod species is presented in Table 3 and it shows an impressing close affinity between the assemblages from south-western Nigeria, those from Mali, Libya, Niger Republic and those observed in the studied Illela borehole rock samples from Northwestern Nigeria. The similarity of the ostracod assemblages between North Africa (Libya), Iullemeden Basin (Illela borehole, Mali and Niger Republic) and South-western Nigeria had been employed by researchers to suggest that a marine connection existed between the Gulf of Guinea and the Sokoto Basin via the area now occupied by the River Niger during the Paleocene (Barsotti, 1963; Kogbe et al., 1976; Reyment, 1978, 1980, 1981 and Carbonnel et al., 1990).

Krithe Kalambainensis (Reyment)



813

Nucleolina Tatteulensis Reyment

Bairdia Ilaroensis (Reyment & Reyment)

Buntonia Beninensis

Paracypris Sokotoensis (Reyment) Plate2: Sketches of ostracods species in the Late Paleocene Dange and Kalambaina Formations, Illela borehole and Gada village

FORAMINI FERA Haplophrag moides Elphidiella africana Cibicides succedens Gavelliinella lellingensis Planulina species Lenticulina Species OSTRACOD S Actinocyther eis asanmamoi Reyment Paracypris sokotoensis Reyment Iorubaella Ologuni Reyment Krithe Kalambainen sis


GA 9

GA 8

GA 7

GA 6

GA 5

GA 4

ILA 72

ILA 71

ILA 65

ILA 64

ILA 62

ILA 61

ILA 60

ILA 59

ILA 58

ILA 56

ILA 55

ILA 54

ILA 53

ILA 52

ILA 51

ILA 50

ILA 49

ILA 48

ILA 47

ILA 46

ILA 28

ILA23

ILA 19

SAMPLE NUMBER

Table2: Distribution of foraminifera and ostracods species showing the relative abundance of different species

Paleobiogeography and Depositional Environment of the Maastrichtian-Late Paleocene Dange Shale, Sokoto Basin, NW Nigeria

814

Reyment Bairdia Ilaroensis, Reyment and Reyment Buntonia beninensis Reyment

- Common

- Few

- Rare

Table3: Paleobiogeographic distribution of the available ostracod species in Illela borehole and comparison with Apostolescu, 1961; Barsotti, 1963; Reyment, 1963, 1978, 1980, 1981 and Carbonnel et al., 1990. Countries/ basins Ostracod species

Nigeria (SW)

Nigeria (NW) Illela

Niger Republic South

Niger Republic North

Bairdia Ilaroensis, R & R

X

X

X

X

X

Iorubaella Ologuni, R

X

X

X

X

X

Paracypris sokotoensis, R

X

X

X

X

Buntonia Beninensis, R

X

X

Krithe Kalambainensis R

X

X

X

Nucleolina tatteulensis (A)

X

X

X

Libya

Mali

X X

X

Senegal

X

X

R & R = Reyment & Reyment, A = Apostolescu, R = Reyment, SW = Southwest, NW = Northwest 1.2.4. Discussion and conclusion: The Maastrichtian - Late Paleocene Dange shale and the Kalambaina limestone were deposited during the transgressive phase of the Paleocene cyclothem (Petters, 1978) and were characterized by marine development. Petters (1978) suggested that the Kalambaina limestone had abnormal hyper saline condition based on alpha-values of 3 and the occurrence of an association of miliolids at the base of the formation. The studied borehole section is delineated into upper foraminifera and lower ostracod biostratigraphic units. No formal biostratigraphic zonation could be attempted this is due to the absence of planktonic foraminifera, low diversity of both benthic foraminifera assemblages and the marine ostracods. Thus, the similarity of the ostracod assemblages between North Africa (Libya), Iullemeden Basin (Illela borehole, NW Nigeria, Mali and Niger Republic) and South-western Nigeria suggests that a marine connection existed between the Gulf of Guinea and the Sokoto Basin via the area occupied by the River Niger during the Paleocene. 2.

Acknowledgement:

I thank Dr Rafiu Babatunde Bale (H.O.D) Geology, University of Ilorin, for his advice and encouragement, also Dr Olabisi Adekeye, Geology Department,

University of Ilorin, he is highly recognized too for his advice and the materials given to me during this research work. I also thank Mr. Yinka Bello, MD Energy field limited for his financial support during this research work as well. My wife, Raliat Aliyu Abdulkareem, is also acknowledged. 3.

Reference:

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temoignage de l’existence eventualle de la mer tanss aharienne? Geobioss,23(6), p. 671-697 [6] Jones, B., 1948; the sedimentary rocks of Sokoto provinces. Bulletin Geological Survey Nigeria, 18, 1-75. [7] Kogbe, C.A. 1976; Outline of the Geology of the Iullemmeden Basin in north– western Nigeria. In: Geology of Nigeria (Edited by Kogbe, C. A), pp.331 – 338 Elizabethan Pub. Co., Lagos, Nigeria. [8] Kogbe, C.A., Le Aclver, Y., Crekoff, N., Mehes, K. 1976; Micro biostratigraphy of lower Tertiary sediments from the south-eastern flanks of the Iullemmeden Basin (northwest Nigeria). In Kogbe C.A. ed Geology of Nigeria Elizabethan Publ. Co., Lagos.p.339-343. [9] Kogbe, C.A 1979; Geology of the south-eastern (Sokoto) sector of the Iullemmeden Basin. Bulletin Department of Geology, Ahmadu Bello University, Zaria, Nigeria. 2 (1), xv + 420pp [10] Kogbe, C.A. 1981; Cretaceous and Tertiary of the Iullemmeden Basin in Nigeria (West Africa). Cret. Res. 2, pp. 129 – 186. [11] Murray, J.W., 1991a; Ecology and paleoecology of Benthic Foraminifera. Longman Group. U.K. Ltd.,397pp

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