Gravity field and tectonic features of Block L2 in the Lamu basin, Kenya

Xie, Wensheng; Gui-he, Liu; Zhang, Chunguan

doi:10.1111/j.1365-2478.2011.00961.x

Cited by 11 publications

(11 citation statements)

References 10 publications

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“…In contrast, sediment thicknesses in the domain of the eastern basins are much larger, pointing also to larger porosity variations (due to differential states of compaction). Our model is consistent with the available information on porosity-controlled density increase in the Anza (Jose and Romanov, 2012) and Lamu basins (Yuan et al, 2012). Assuming an alternative scenario of a fully compacted sediment package in the eastern basins domain with a homogeneous bulk density of 2710 kg m −3 , for instance, would increase the gravity response locally by up to +80 mGal.…”

Section: Model Sensitivity and Robustnesssupporting

confidence: 86%

“…Deposits of the Lamu Basin are lithologically described as a repetitive sequence of mainly siliciclastic rocks (sandstones, siltstones, shales) and intercalated limestones (Nyagah, 1995; Table 1). Direct evidence on the density configuration of the basin infill is provided by the study of Yuan et al (2012), who jointly investigated reflection seismic and gravity data from the central Lamu Basin. According to these observations, density increases with depth and age of the depositional sequences (the main ones of which are of Cenozoic, Cretaceous, Jurassic and Permian/Triassic ages).…”

Section: A1 Eastern Kenyamentioning

confidence: 99%

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The Kenya rift revisited: insights into lithospheric strength through data-driven 3-D gravity and thermal modelling

et al. 2017

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Abstract. We present three-dimensional (3-D) models that describe the present-day thermal and rheological state of the lithosphere of the greater Kenya rift region aiming at a better understanding of the rift evolution, with a particular focus on plume–lithosphere interactions. The key methodology applied is the 3-D integration of diverse geological and geophysical observations using gravity modelling. Accordingly, the resulting lithospheric-scale 3-D density model is consistent with (i) reviewed descriptions of lithological variations in the sedimentary and volcanic cover, (ii) known trends in crust and mantle seismic velocities as revealed by seismic and seismological data and (iii) the observed gravity field. This data-based model is the first to image a 3-D density configuration of the crystalline crust for the entire region of Kenya and northern Tanzania. An upper and a basal crustal layer are differentiated, each composed of several domains of different average densities. We interpret these domains to trace back to the Precambrian terrane amalgamation associated with the East African Orogeny and to magmatic processes during Mesozoic and Cenozoic rifting phases. In combination with seismic velocities, the densities of these crustal domains indicate compositional differences. The derived lithological trends have been used to parameterise steady-state thermal and rheological models. These models indicate that crustal and mantle temperatures decrease from the Kenya rift in the west to eastern Kenya, while the integrated strength of the lithosphere increases. Thereby, the detailed strength configuration appears strongly controlled by the complex inherited crustal structure, which may have been decisive for the onset, localisation and propagation of rifting.

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Section: Model Sensitivity and Robustnesssupporting

confidence: 86%

Section: A1 Eastern Kenyamentioning

confidence: 99%

The Kenya rift revisited: insights into lithospheric strength through data-driven 3-D gravity and thermal modelling

et al. 2017

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“…To understand the style of margin formation in the WSB, we draw together a combination of seismic, gravity, magnetic, and geological evidence. Coffin et al [1986] confirmed the existence of oceanic crust just offshore of the Kenya-Somalia border as far north and west as 42.058E 2.528S, but inboard of this within the Tanzania Coastal Basin and extending onshore within the Lamu Embayment, thin crust (<13 km thick) [Reeves et al, 1987] of an ambiguous nature is covered by thick sediments (up to 112 km, Yuan et al [2012] and references therein). Based on gravity and magnetic modeling, Reeves et al [1987] proposed that this crust is oceanic in nature, consistent with observations of necking zones (as defined by Tugend et al [2015]) onshore along the western edge of the Lamu Embayment from seismic refraction data, which suggest sharp crustal thinning from over 40 km to probably less than 15 km at this location [Prodehl et al, 1997].…”

Section: Plate Tectonic Modelmentioning

confidence: 73%

Madagascar's escape from Africa: A high‐resolution plate reconstruction for the Western Somali Basin and implications for supercontinent dispersal

Phethean

Kalnins

Hunen

et al. 2016

Geochem Geophys Geosyst

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Accurate reconstructions of the dispersal of supercontinent blocks are essential for testing continental breakup models. Here, we provide a new plate tectonic reconstruction of the opening of the Western Somali Basin during the breakup of East and West Gondwana. The model is constrained by a new comprehensive set of spreading lineaments, detected in this heavily sedimented basin using a novel technique based on directional derivatives of free‐air gravity anomalies. Vertical gravity gradient and free‐air gravity anomaly maps also enable the detection of extinct mid‐ocean ridge segments, which can be directly compared to several previous ocean magnetic anomaly interpretations of the Western Somali Basin. The best matching interpretations have basin symmetry around the M0 anomaly; these are then used to temporally constrain our plate tectonic reconstruction. The reconstruction supports a tight fit for Gondwana fragments prior to breakup, and predicts that the continent‐ocean transform margin lies along the Rovuma Basin, not along the Davie Fracture Zone (DFZ) as commonly thought. According to our reconstruction, the DFZ represents a major ocean‐ocean fracture zone formed by the coalescence of several smaller fracture zones during evolving plate motions as Madagascar drifted southwards, and offshore Tanzania is an obliquely rifted, rather than transform, margin. New seismic reflection evidence for oceanic crust inboard of the DFZ strongly supports these conclusions. Our results provide important new constraints on the still enigmatic driving mechanism of continental rifting, the nature of the lithosphere in the Western Somali Basin, and its resource potential.

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“…The Permo‐Carboniferous to Tertiary sedimentary section consists of a seaward thickening sedimentary wedge, including continental rift basin sandstones, fluviodeltaic sandstones, marine shales, and carbonates. The sedimentary section has a minimum onshore thickness of 3 km, reaches about 10 km in the coastal areas, and is up to 13 km thick in the offshore depocenter [ Nyagah, ; Yuan et al, ].…”

Section: Regional Geological Frameworkmentioning

confidence: 99%

“…The sedimentary section has a minimum onshore thickness of 3 km, reaches about 10 km in the coastal areas, and is up to 13 km thick in the offshore depocenter [Nyagah, 1995;Yuan et al, 2012].…”

Section: Stratigraphymentioning

confidence: 99%

The Lamu Basin deepwater fold‐and‐thrust belt: An example of a margin‐scale, gravity‐driven thrust belt along the continental passive margin of East Africa

Cruciani

Barchi

2016

Tectonics

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In recent decades, advances in seismic processing and acquisition of new data sets have revealed the presence of many deepwater fold-and-thrust belts (DW-FTBs), often developing along continental passive margins. These kinds of tectonic features have been intensively studied, due to their substantial interest. This work presents a regional-scale study of the poorly explored Lamu Basin DW-FTB, a margin-scale, gravity-driven system extending for more than 450 km along the continental passive margin of Kenya and southern Somalia (East Africa). A 2-D seismic data set was analyzed, consisting of both recently acquired high-quality data and old reprocessed seismic profiles, for the first detailed structural and stratigraphic interpretation of this DW-FTB. The system originated over an Early to mid-Cretaceous shale detachment due to a mainly gravity-spreading mechanism. Analysis of synkinematic strata indicates that the DW-FTB was active from the Late Cretaceous to the Early Miocene, but almost all of the deformation occurred before the Late Paleocene. The fold-and-thrust system displays a marked N-S variation in width, the northern portion being more than 150 km wide and the southern portion only a few dozen kilometers wide; this along-strike variation is thought to be related to the complex tectonosedimentary evolution of the continental margin at the Somalia-Kenya boundary, also reflected in the present-day bathymetry. Locally, a series of volcanic edifices stopped the basinward propagation of the DW-FTB. A landward change in the dominant structural style, from asymmetric imbricate thrust sheets to pseudo-symmetric detachment folds, is generally observed, related to the landward thickening of the detached shales.

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Gravity field and tectonic features of Block L2 in the Lamu basin, Kenya

Cited by 11 publications

References 10 publications

The Kenya rift revisited: insights into lithospheric strength through data-driven 3-D gravity and thermal modelling

The Kenya rift revisited: insights into lithospheric strength through data-driven 3-D gravity and thermal modelling

Madagascar's escape from Africa: A high‐resolution plate reconstruction for the Western Somali Basin and implications for supercontinent dispersal

The Lamu Basin deepwater fold‐and‐thrust belt: An example of a margin‐scale, gravity‐driven thrust belt along the continental passive margin of East Africa

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