Mineralogy of the Wembere-Manonga Formation, Manonga Valley, Tanzania, and the Possible Provenance of the Sediments

Abstract

This chapter presents the results of geological fieldwork conducted in the Manonga Valley, northern Tanzania, during the summer of 1994, in conjunction with the stratigraphic and paleomagnetic studies of Drs. Jacques Verniers (University of Gent) and John Kappelman (University of Texas at Austin). The research area and the location of the sites discussed in this chapter are described in detail by Harrison and Mbago (this volume, Chapter 1) and by Verniers (this volume, Chapter 2). Deposits in the Manonga depression consist of a series of fluvio-lacustrine sediments, ranging from 25 to 200 m in thickness (Kassim, 1994; Verniers, this volume, Chapter 2). The lowermost beds consist of a layer of conglomerates, up to 5 m thick, which compose the Mwansarara Formation. This is overlain by a thick series of fine- to medium-grained sediments, primarily consisting of swelling clays with calcretes and red beds (latosols), that together make up the Wembere-Manonga Formation. The aim of this Chapter is to provide a brief description of rock samples obtained from three naturally exposed profiles of the Wembere-Manonga Formation, and to report on preliminary findings of mineralogical analyses.