Interplay between structural, climatic and volcanic controls on Late Quaternary lacustrine-deltaic sedimentation patterns in the Western Branch of the East African Rift System, Rukwa Rift Basin, Tanzania

Mtelela, Cassy, Roberts, Eric M., Downie, Robert, and Hendrix, Marc S. (2016) Interplay between structural, climatic and volcanic controls on Late Quaternary lacustrine-deltaic sedimentation patterns in the Western Branch of the East African Rift System, Rukwa Rift Basin, Tanzania. Journal of Sedimentary Research, 86 (10). pp. 1179-1207.

[img] PDF (Published Version) - Published Version
Restricted to Repository staff only

View at Publisher Website: http://dx.doi.org/10.2110/jsr.2016.73
 
3
7


Abstract

his paper presents the first detailed, outcrop-based sedimentologic investigation of the Pleistocene–Holocene upper Lake Beds succession in the Rukwa Rift Basin, located in the Western Branch of the East African Rift System, southwestern Tanzania. The goal of this investigation is to examine the sedimentary facies and reconstruct the depositional environments of this important archive of Quaternary climate and environmental change. Eleven diagnostic facies associations comprising 24 facies were identified and provide the basis for recognition of three key deposystems: 1) alluvial-to-fluvial channel system; 2) lake delta system; and 3) profundal lacustrine system. Analysis of paleocurrent indicators and sandstone provenance indicate widely dispersed source regions and drainage patterns that were strongly influenced by major border-fault systems and episodic volcanism. Six stratigraphic sequences (A–F), ranging from ~ 2 to 17 m thick, were identified based on stratal stacking patterns and the development of sequence-bounding unconformities and lacustrine flooding surfaces. Sedimentation processes, facies architecture, and stratigraphic packaging record a complex interplay between Quaternary climate fluctuations and intense episodic volcanism in the nearby Rungwe Volcanic Province, set against large-scale tectonic controls associated with synchronous development of the East African Rift System. Sequence stratigraphic analysis reveals that the Rukwa Rift Basin episodically shifted between a balanced-fill lake basin and an overfilled lake basin. Deep water, basin-wide lake expansion occurred at different times during the late Quaternary. The final depositional sequence preserved in the basin, a fluvial–underfilled lake basin, initiated ~ 7.9 ka and has persisted to the present day. High-frequency climate change played the key role in sequence development in the upper Lake Beds. However, voluminous, rift-related volcanism and erosion of abundant labile volcanic materials from the Rungwe Volcanic Province, as well as syntectonic evolution of the rift, led to high sedimentation rates and transformation of flash floods and debris flows in the hinterlands (rift margin) to hyperpycnal flows towards the basin depocenter.

Item ID: 47290
Item Type: Article (Refereed Research - C1)
ISSN: 1938-3681
Funders: Tanzania Petroleum Development Corporation (TPDC), Heritage Oil Rukwa Tanzania Ltd. , United States National Science Foundation (NSF), National Geographic Society (CRE), James Cook University (JCU) Graduate Research Fund
Projects and Grants: NSF EAR_1349825, NSF BCS_1127164
Date Deposited: 22 Feb 2017 02:03
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040310 Sedimentology @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 50%
85 ENERGY > 8501 Energy Exploration > 850103 Oil and Gas Exploration @ 50%
Downloads: Total: 7
More Statistics

Actions (Repository Staff Only)

Item Control Page Item Control Page