DETERMINATION OF THE SEDIMENTOLOGICAL AND GEOCHEMICAL CHARACTERISTICS OF THE SEDIMENT IN THE NIGER DELTA BASIN
CHAPTER ONE
INTRODUCTION
The mineralogical and chemical composition of clastic sedimentary rocks are controlled by various factors, including (1) the composition of their source rocks, (2) environmental parameters influencing the weathering of source rocks (e.g., atmosphericchemistry, temperature, rainfall and topography), (3) duration of weathering (4)transportation mechanisms of clastic material from source region to depocenters, (5)depositional environment (e.g., marine versus fresh water), and (6) post-depositional processes (e.g., diagenesis, metamorphism) (Hayashi et al., 1997). Numerousinvestigations are substantiating the above aspects pertaining to genesis of both ancient andmodern siliciclastic sediments (e.g., Dickenson et al., 1983; Nesbitt and Young, 1982, 1984; Bhatia, 1983; Roser and Korsch, 1988; McCann, 1991; Condie et al., 1992; Condie, 1993; McLennan et al., 1993; Nesbitt et al., 1996; Cullers, 2000; Hessler and Lowe 2006; Nagarajan et al., 2007; Spalletti et al., 2008). Several studies have also been focused on the identification of palaeotectonic settings of provenances based on geochemical signatures of siliciclastic rocks (e.g., Dickinson and Suczek, 1979; Bhatia, 1983; Bhatia and Crook, 1986; Roser and Korsch 1986; McLennan and Taylor, 1991). Among the terrigenous sedimentary rocks, shales are considered to represent the average crustal composition of the provenance much better than any other siliclastic rocks (e.g., McCulloch and Wasserburg, 1978). Shales retain most of the mineral constituents of the source and their bulk chemistry preserves the near-original signature of the provenance and more faithfully reveal palaeoweathering conditions (e.g., Pettijohn, 1975; Graver and Scott, 1995). The present note examines the geochemistry of sediment from part of the subsurface Niger Delta Basin province, attempts to constrain there paleo redox and tectonic setting and provenance. Owing to limitations of analytical facilities, the present work is based on chemical analyses data of major and select trace elements of the investigated sediment of the study area.
