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.