Subsurface structure and stratigraphy of the northwest end of the Turkana Basin, Northern Kenya Rift, as revealed by magnetotellurics and gravity joint inversion

Abstract

In order to understand the subsurface stratigraphy and structure of the northwest end of the Turkana Basin, Northern Kenya Rift, we used 2-D joint inversion of magnetotelluric (MT) and gravity data acquired along 3 profiles perpendicular to the main Murua Rith-Lapur Rift Border Fault. The regional geology is characterized by a basement of Precambrian age overlain by a ≤500-m thick sandstone formation named the Lapur

Influence of Rift Superposition on Lithospheric Response to East African Rift System Extension: Lapur Range, Turkana, Kenya

“…This is particularly apparent when considering that total crustal extension across the Anza rift is estimated to be 60–65 km, equating to a beta factor (β) of ~2 (Reeves et al, ) compared to the relatively minor degree across the Kenyan rift ( β = ~1.15) (Latin et al, ). An erosional unconformity in the Lapur Sandstone type section ~150 m above the basement nonconformity, however, may represent a period of significant erosion and removal of an unknown thickness of sediment (Abdelfettah et al, ), perhaps allowing for greater Upper Cretaceous sedimentation undetected by low‐temperature thermochronology due to later rejuvenation of the system. The identification of thick piles of sediment in the subsurface of the northern Turkana, Gatome, and Lotikipi Basins (up to 300, 800, and 3,000 m, respectively) thought to possibly correspond to the Lapur Sandstone (Tiercelin et al, ; Wescott et al, ) suggests that Late Cretaceous‐early Paleogene sedimentation may have been far more laterally extensive (~100 km E‐W) than outcrop observations would suggest.…”

“…The Lapur Range, attaining elevations of up to 1,560 m above sea level, is located along the northwest shores of Lake Turkana at the intersection of the failed Anza‐South Sudan Rifts (Figure ). The Lapur block sits in the footwall of the MRL Fault, a N‐S trending, east dipping normal fault that bounds the western side of the northern Turkana Basin (Figure a) (Abdelfettah et al, ; Morley et al, ; Tiercelin et al, ). The northern Turkana Basin is a generally N‐S trending, westward dipping half graben that hosts present‐day Lake Turkana.…”

“…The location of seismic line TVK‐10 (Figure a) is illustrated in black (Wescott et al, ). Adapted from Walsh and Dodson () and Abdelfettah et al ().…”

Crustal Structure of Active Deformation Zones in Africa: Implications for Global Crustal Processes

“…Black dashed line is the approximate surface contact between Archaean and Pan‐African crust. Triangles and inverted triangles are locations of broadband seismic data sets (Albaric et al, ; Dugda et al, ; Gao et al, ; Last et al, ; Plasman et al, ; Tugume et al, ; Velasco et al, ; Weinstein et al, ), and circles and hexagons are locations of intermediate and long‐period MT recordings (Abdelfettah et al, ; Hautot et al, ; Hautot & Tarits, ; Sakkas et al, ; Selway et al, ; Simpson, ). Bold lines are approximate locations of the Kenya Rift International Seismic Project (KRISP) wide angle reflection/refraction and MT profiles as outlined in Prodehl et al () and Khan et al ().…”

Evolution of the northern Turkana Depression (East African Rift System, Kenya) during the Cenozoic rifting: New insights from the Ekitale Basin (28‐25.5 Ma)

“…In contrast, the northern part of the Turkana Depression (Figure 1 b), markedly less well known, consists of a single 80-km-wide, >4-kmdeep (Abdelfettah et al, 2016) N-S-oriented asymmetric graben known as the North Lake Basin (Figure 1c; Hendrie, Kusznir, Morley, & Ebinger, 1994;Morley et al, 1999;Tiercelin et al, 2004;Vétel & Le Gall, 2006). The North Lake Basin forms a narrow rift (sensu Buck, 1991) and is bounded to the west by the N-S-oriented Murua Rith-Lapurr Fault (MRLF, Figure 1b).…”