1) Upper Cretaceous Sequences of the Southern Bida Basin, Central Nigeria.

Introduction:

Date: Friday, November 19, 2004 (trip departs from and returns to Abuja Sheraton)

Leaders: Sam Akande (Unilorin, Geology) & Sola Ojo (Unilorin Geology) Kenny Ladipo ( SPDC ).

Fee: $150.00 (includes transportation, lunch pack and guidebook)

Limit: 25 persons

Attendees will gain insight into the stages of intracratonic rift basin evolution during the Upper Cretaceous in the Lokoja – Abaji areas of Central Nigeria. Alluvial fans, braided streams and tidally influenced marginal marine deposits will be observed in outcrops along the Lokoja – Abaji Highway. The stacked clastic sediments comprise of the Campanian to Maastrichtian Lokoja Sandstone Formation, the Maastrichtian Patti Formation and the Agbaja Ironstones representing the continental to marginal marine sequences of the North -Westerly trending Bida Basin which extends South-Easterly into the contiguous Anambra Basin (the precursor of the oil producing Niger delta Basin). The locations selected display excellent outcrop scenarios of the sedimentological characteristics of conglomerates, sandstones, shales, siltstones, mudstone and claystone facies of the Upper Cretaceous formations representing debris flow, braided stream flows, abandoned channels and flood plain deposits. Aspects of sequence stratigraphy, sedimentology and reservoir quality predictions will be discussed at each stop while special emphasis on the significance of the sedimentary and biogenic structures will be highlighted during the trip. Active participation by attendees in the discussions is encouraged.

Shale facies of the Patti Formation interbedded with concretionary ironstones and bioturbated mudstones (flood plain deposits) on the Ahoko section. Photo courtesy of Sam O. Akande.

2) Upper Cretaceous to Tertiary Sequences of the Anambra Basin, Southeastern Nigeria.

Introduction:

Date: Friday, November 19, 2004 (trip departs from Abuja Sheraton to Enugu Zodiac Hotel for overnight accommodation) and returns to Abuja on the 4th day for most participants giving 3 night accommodation in the Enugu base camp.

Leaders: Prof. C.S. Nwajide (HRW-SITP, SPDC, Warri), Dr.G.C. Obi (Geology, University of Nigeria, Nsukka), Theo Duze (TotalFinaElf).

Fee: $500 (include transportation, guidebook, accommodation and feeding in Enugu).

Limit: 20 persons .

The Anambra Basin is one of the Upper Cretaceous to Tertiary derivative basins of the Benue Trough and, with the Dahomey and Niger Delta Basins, is also one of the oil and gas basins of Nigeria. Its landscape is dominated by a ca. 500km long sinuous shaped cuesta, the scarp face of which offers the best and most accessible exposures. A two day trip, with Enugu City as the logistics base, allows participants a view of some aspects of the dominantly clastic basin fill. Enugu City also offers some glimpses of the local culture. Excellent exposures are available along river channels as well as the Miliken Hills in the greater Enugu area.
Easy to access and study are paleosols, ancient channels, incoaling features (coal seams, rooting and seat earth) and soft sediment deformation structures such as growth fault and roll over anticline, atectonic fold limbs and contorted beds of sandstone). South of Enugu , there are road cut exposures of extensional faults within the black shales and heteroliths of the Campanian Enugu Formation. The cuesta scarp exposes black shale – sandstone alternations, interbeds of oolitic ironstones in black shales, and such key stratigraphic features as sequence boundaries, ravinement surface, deepening upward, and shallowing upward parasequences. Farther south, and further up the cuesta scarp, a cashew –forested sandstone formation yields to the Upper Coal Measure succession below which the aforementioned sandstone is again exposed and is being exploited as a major building material being exploited in the Onyekaba quarry at the northern outskirts of Okigwe town. Exposed in the quarry is a Maastrichtian succession of relatively clean sand characterized by such structures as channeling, large- scale asymmetrical ripples, interference ripples, clay-draped planar and trough cross-beds, flaser bedding, diagenetic (lisengang) structures, as well as burrows of the Glossifungites (firmground) and Skolithos ichnofacies.

Caption: Ichnogenera of the Glossifungites Ichnofacies on an intensely bioturbated firmground taken as a marker horizon subdividing the Maastrichtian Ajali Formation exposed in a quarry north of Okigwe , Imo State.