Sedimentologic And Paleocurrent Analysis Of The Early Triassic Strata In The Ruhuhu Basin, Tanzania

ABSTRACT

Ruhuhu basin has eight informal lithostratigraphic units, termed the K1 to K8.This research was conducted at Lifua Member (formally K8). The beds are of Early Triassic and are the youngest stratigraphic unit of the Karoo strata in the RuhuhuBasin. This research applies sedimentology and paleocurrent analysisof the early Triassic strata in interpreting provenance, shape and orientation andreconstructing paleogeography of this unit.It involved description, measurements and sampling of the rocks from theoutcrops as well as grain size analysis, geochemistry and petrographic studies.Based on the present study, about five lithofacies were identified namelyMassive matrix supported paraconglomerate (Gmm), Massive sandstone(Sm), Parallel-horizontal lamination (Sh), Planar cross beds (Sp) and fine silt, mud and clay (Fl).Most of the sandstone exhibited normal grading caused by decrease in energy of the river current. Grain size analysis indicates that sandstone is moderately sorted, finely skewed, mesokurtic and that most of the grains are silty sand. These two suggestfluviatile dominated by sand channel deposition environment.Grain size analysis and petrographyclassified the sandstone as sublitharenite and chemically as ferruginous quartzose. Maturity level is from submature to mature sediments, which suggest source area was of low relief and warm, humid climate where chemical weathering was moderately intense. Geochemistry and Heavy mineral suit suggested basic igneous rock as the provenance of the sandstone.Paleocurrent was from NW towards SE, although some were also from various localized area. The shape of the basin is elongated NE/SW. Based on the observations,Lifua Member has a good reservoir rock due to dominant mode of channel deposit and textural characteristics of the sandstone.