3.2. Heavy mineral analysis
The ZTR index was calculated to ascertain the mineralogical
maturity (Table 2). The ZTR ternary plot is also presented (Fig. 8).
The value falls within the range of 22%e35% with an average of
27.6% which indicates mineralogically immature sediments
(Hubert, 1962). Hubert (1962) reported that the non-opaque heavy
mineral assemblages, predominantly zircon, tourmaline, and rutile,
are ultimately concentrated in sandstone by prolonged abrasion
occurring during transportation. The younger sediments generally
contain a greater number of different heavy mineral species than
older rocks. Heavy minerals of Paleozoic sediments consist entirely
of the most stable species such as zircon, tourmaline, rutile, and
garnet (Pettijohn, 1941; Hubert, 1962). This is attributed to
diagenesis as the older rocks are more susceptible than the younger
rocks, as evident in the study area. The heavy mineral assemblage
shows that the origin of the coastal plain clastic deposits of the
study area could be metamorphic rocks as indicated by the abundance
of staurolite (Hubert, 1962). The presence of zircon, garnet,
Fig. 6. Lithostratigraphic sections correlation for the three wells.
O.A. Boboye, O.R. Nwosu / Quaternary International 338 (2014) 14e27 19
and tourmaline in the sediment indicates that parts of the sediments
were derived from acidic igneous rocks, as well as from preexisting
sedimentary rocks. The presence of staurolite and kyanite
in the studied samples indicate middle to high grade metamorphic
rocks. The heavy mineral assemblage from these wells could have
been sourced from the adjoining crystalline rocks of the Basement
Complex.