Geologic Map of Oldonyo Lengai (Oldoinyo Lengai) Volcano and Surroundings, Arusha Region, United Republic of Tanzania

Introduction

The geology of Oldonyo Lengai volcano and the southernmost Lake Natron basin, Tanzania, is presented on this geologic map at scale 1:50,000. The map sheet can be downloaded in pdf format for online viewing or ready to print (48 inches by 36 inches).

A 65-page explanatory pamphlet describes the geologic history of the area. Its goal is to place the new findings into the framework of previous investigations while highlighting gaps in knowledge. In this way questions are raised and challenges proposed to future workers.

The southernmost Lake Natron basin is located along the East African rift zone in northern Tanzania. Exposed strata provide a history of volcanism, sedimentation, and faulting that spans 2 million years. It is here where Oldonyo Lengai, Tanzania’s most active volcano of the past several thousand years, built its edifice. Six new radiometric ages, by the ⁴⁰Ar/³⁹Ar method, and 48 new geochemical analyses from Oldonyo Lengai and surrounding volcanic features deepen our understanding of the area.

Those who prefer the convenience and access offered by Geographic Information Systems (GIS) may download an electronic database, suitable for most GIS software applications. The GIS database is in a Transverse Mercator projection, zone 36, New (1960) Arc datum. The database includes layers for hypsography (topography), hydrography, and infrastructure such as roads and trails.

First posted January 9, 2014