Subsidence history, crustal structure, and evolution of the Somaliland‐Yemen conjugate margin

Ali, Mohamed; Watts, A. B.

doi:10.1002/jgrb.50113

Cited by 18 publications

(44 citation statements)

References 77 publications

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“…In this case, the calculated tectonic subsidence of ~1800 m during the fast rifting of pristine lithosphere dramatically reduces to <500 m when the same rifting event occurs on previously rifted lithosphere, independent of the previous boundary velocity. Albeit general, these results are in agreement with Ali and Watts [], Cunha [], and Chen [] who used multiple event subsidence models to show the effect of rifting history in specific geological cases such as the Gulf of Aden [ Ali and Watts , ], Iberian margin [ Cunha , ] and Baiyun Sag in the South China Sea [ Chen , ].…”

Section: Discussionsupporting

confidence: 87%

“…Chen [] used a rifting‐cooling‐rifting cycle to model the subsidence in the Baiyun Sag along the continental slope of the South China Sea. A similar modeling strategy was adopted by Ali and Watts [] and Cunha [] to interpret the subsidence history of the Gulf of Aden and the Iberia margin, respectively. Armitage et al .…”

Section: Introductionmentioning

confidence: 99%

“…Chen [2014] used a rifting-cooling-rifting cycle to model the subsidence in the Baiyun Sag along the continental slope of the South China Sea. A similar modeling strategy was adopted by Ali and Watts [2013] and Cunha [2008] to interpret the subsidence history of the Gulf of Aden and the Iberia margin, respectively. Armitage et al [2010] invoked multiple rifting events alternating with cooling periods to explain strain migrations and magma production in the Greenland and southwest Indian margins.…”

Section: Introductionmentioning

confidence: 99%

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The role of long‐term rifting history on modes of continental lithosphere extension

et al. 2016

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Continental lithosphere extension results in complex basin types with differing structural styles, subsidence, thermal histories, and melt production. Many studies have examined the role of initial rheological layering, geothermal gradients, and extension rates during a single rifting event. This approach neglects the tectonic history of many basins that are marked by multiple rifting events. Here we address the role of repeated extension on long‐term lithospheric strain modes and the resulting basins, highlighting cases most affected by previous rifting events. We use numerical models of a lithosphere undergoing two rifting events of differing extension rates and separated by cooling, to show the effect of early events on subsequent evolution. The combination of boundary displacement velocity in both events leads to the formation of various rift basin types, ranging from narrow to wide to hyperextended and with variation of subsidence patterns, degrees of symmetry, and melt yield. We show that basin type, subsidence, and melt production might be strongly affected by previous rifting events, illustrating cases in which the previous rifting history cannot be neglected. Our models reproduce the first‐order features of Earth's sedimentary basins and propose a classification to guide the interpretation of extensional basins and their evolution.

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Section: Discussionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The role of long‐term rifting history on modes of continental lithosphere extension

et al. 2016

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“…Oligocene-Miocene rifting of the Gulf of Aden subjected the conjugate margins of Somaliland (NW Somalia) and southern Yemen to an extensional system of east-west to ENE-WSW striking normal faults which reactivated pre-existing Mesozoic faults (Ali and Watts, 2013;Bellahsen et al, 2013;Leroy et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Petroleum Geology and Hydrocarbon Potential of the Guban Basin, Northern Somaliland

Ali

2015

Journal of Petroleum Geology

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The Guban Basin is a NW-SE trending Mesozoic-Tertiary rift basin located in northern Somaliland (NW Somalia) at the southern coast of the Gulf of Aden. Only seven exploration wells have been drilled in the basin, making it one of the least explored basins in the Horn of Africa --southern Arabia region. Most of these wells encountered source, reservoir and seal rocks. However, the wells were based on poorly understood subsurface geology and were located in complex structural areas.The Guban Basin is composed of a series of on-and offshore sub-basins which cover areas of 100s to 1000s of sq. km and which contain more than 3000 m of sedimentary section. Seismic, gravity, well, outcrop and geochemical data are used in this study to investigate the petroleum systems in the basin. The basin contains mature source rocks with adequate levels of organic carbon together with a variety of reservoir rocks. The principal exploration play is the Mesozoic petroleum system with mature source rocks (Upper Jurassic Gahodleh and Daghani shales) and reservoirs of Upper Jurassic to Miocene age. Maturity data suggest that maximum maturity was achieved prior to Oligocene rift-associated uplift and unroofing. Renewed charge may have commenced during post-Oligocene-Miocene rifting as a result of the increased heat flows and the increased depth of burial of the Upper Jurassic source rocks in localised depocentres. The syn-rift Oligocene-Miocene acts as a secondary objective owing to its low maturity except possibly in localised offshore sub-basins. Seals include various shale intervals some of which are also source rocks, and the Lower Eocene evaporites of the Taleh Anhydrite constitute an effective regional seal. Traps are provided by drag and rollover anticlines associated with tilted fault blocks. However, basaltic volcanism and trap breaching as a consequence of the Afar plume and Oligocene-Miocene rifting of the Gulf of Aden cause considerable exploration risk in the Guban Basin.

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“…The basin contains both Upper Jurassic source rocks and a variety of reservoir rocks. Furthermore, by backstripping biostratigraphic data from exploration wells Ali and Watts (2013) and Ali and Watts (2016) showed that basins in northern Somalia have undergone three main rift phases with intervening periods of uplift and erosion. Initial phases of rifting occurred in the Late Jurassic and Late Cretaceous as a result of the late-stage break-up of Gondwana and a rapid increase in the spreading rate on the ridges separating the African and Indian plates respectively (Ali and Watts, 2016).…”

Section: Introductionmentioning

confidence: 99%

Petroleum Geology of the Nogal Basin and Surrounding Area, Northern Somalia: Part 1, Stratigraphy and Tectonic Evolution

Ali

Lee

2018

Journal of Petroleum Geology

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In this study, 92 closely‐spaced reflection seismic profiles (∼4000 line‐km) were tied to biostratigraphic and lithological data from six deep exploration wells in the poorly‐known Nogal rift basin, northern Somalia, and were integrated with outcrop and aeromagnetic data to investigate the basin stratigraphy and tectonic evolution. Aeromagnetic data show NW‐SE trending magnetic anomalies which are interpreted as plutonic bodies intruded during the Early Cretaceous, probably contemporaneously with a pre‐Cenomanian uplift phase. The aeromagnetic data also suggest a change of basement type from Inda Ad Series metasediments in the SE of the study area to igneous and high‐grade metamorphic basement in the NW. Biostratigraphic data and seismic reflection profiles define the Nogal Basin as a WNW–ESE striking half‐graben, approximately 250 km long and 40 km wide, which formed as a result of mainly Cenomanian–Maastrichtian and Oligocene–Miocene intracontinental rifting. The depocentre contains at least 7000 m of Mesozoic and Cenozoic sediments and is located in the centre of the basin (east of well Nogal‐1), to the south of the Shileh Madu Range. To the north, the basin is bounded by a major border fault along which significant variations in the thickness of sedimentary units are observed, suggesting that the fault controlled basin architecture and patterns of sedimentation. Oligocene–Miocene normal faults which resulted in north‐tilted fault blocks are widespread within the main basin; smaller‐scale sub‐basins oriented NW‐SE to WNW‐ESE are observed to the NW of the basin and probably developed contemporaneously. The Late Jurassic rift phase which has been documented elsewhere in northern Somalia is either missing in the Nogal Basin or is preserved only in localised grabens in the western and central parts of the basin. This is probably due to the pre‐Cenomanian uplift and erosion which removed almost the entire Jurassic and Lower Cretaceous successions over a wide area referred to as the Nogal‐Erigavo Arch. A more pronounced rifting episode followed this erosional event in the Cenomanian–Maastrichtian and resulted in the deposition of well‐sorted fluvio‐deltaic sandstones (Gumburo and Jesomma Formations), more than 2000 m thick. In wells in the Nogal Basin, these formations are between two and three times thicker than in wells drilled in footwall locations, and include excellent reservoir rocks sealed by transgressive mudstones and carbonates. A final rifting event in the Oligocene–Miocene was related to the opening of the Gulf of Aden. A rift sag phase which accommodated the Early Oligocene continental sediments of the Nogal Group initially developed at the centre of the basin. This was followed by a period of strong rotational faulting and tilting, which reactivated the Cenomanian–Maastrichtian structures.

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Subsidence history, crustal structure, and evolution of the Somaliland‐Yemen conjugate margin

Cited by 18 publications

References 77 publications

The role of long‐term rifting history on modes of continental lithosphere extension

The role of long‐term rifting history on modes of continental lithosphere extension

Petroleum Geology and Hydrocarbon Potential of the Guban Basin, Northern Somaliland

Petroleum Geology of the Nogal Basin and Surrounding Area, Northern Somalia: Part 1, Stratigraphy and Tectonic Evolution

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