Provenance and Tectonic Setting of Amasiri Sandstone (Turonian) in Ugep Area, Southern Benue Trough, Nigeria: Evidences from Petrography and Geochemistry

bstract

The p

rographic and geochemical study of sandstones of Eze

Aku Formation (Turonian)

outcropping in Ugep area souther

n Benue Trough Nigeria was carried out to ascertain the sandstone

provenance and tectonic setting. Field studies show that the sandones occur in linear, parallel northeast

southwest trending ridges alternating with shale sequence. The sandstone facies show

coarsening

upward sequence, slightly bioturbated, cross

stratified, rippled bedded which infer foreshore to shallow

marine below wave base. Petrographic studies show the occurrence of quartz, feldspar, rock fragments

and muscovite. The calculated framework grains suggest feldsparthic (subarkosic) sandstone. The

geochemical analysis of the major elements of the sandstones show that they are enriched in SiO

, TiO

and Fe

and depleted in K

O, Na

O, MgO and CaO. Tectonic setting discrimination plot

iagrams based on major elements suggest the provenance for the sandstones to be of metamorphic

and igneous rocks of Passive Continental Margin Basin. The results of petrographic and geochemical

study suggest Oban Massif and Cameroon Basement as the source regions for the sandstone which are

characterized by humid climate and low

relief during the Turonian.

Keyw

ords :

eze-

aku fo

rmation, petrography, geoche

mistry, sandst

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