Ian Deighton - Academia.edu (original) (raw)

Papers by Ian Deighton

The structural style of the African Atlantic margin shows significant differences between the pas... more The structural style of the African Atlantic margin shows significant differences between the passive rifted Northwest African Atlantic Margin (offshore Senegal, Gambia, Guinea Bissau and Guinea) and the West African Transform Margin (from Sierra Leone to Benin). Recently acquired seismic data provides good quality imaging (down to the Moho in deepwater areas) that allows an understanding of the structural development since the initiation of the opening of the Atlantic Ocean at the end of the Jurassic and gives insights into the present day structural styles and how they developed.

Proc. Indon Petrol. Assoc., 36th Ann. Conv.

Journal of Asian Earth Sciences, 2021

We present a morphotectonic study of the offshore northern Sumatra fore-arc high and fore-arc bas... more We present a morphotectonic study of the offshore northern Sumatra fore-arc high and fore-arc basin and an evolutionary model of the area based on high-resolution marine geophysical datasets. We show that the landward slope of the fore-arc high and the western edge of the Aceh fore-arc basin host a set of deeply-rooted, seaward-dipping backthrusts: main backthrust (MBT) and frontal backthrust (FBT), which we call north Sumatra backthrust system (NSBS). The FBT is imaged reaching the seafloor throughout the study area, whereas the MBT is imaged as a blind fault. Many landward-dipping imbricated thrusts (fore-arc high thrusts-FHT) are also observed below the fore-arc high, which along with the system of backthrusts have been responsible for uplifting the fore-arc high, shortening the Aceh Basin. On the landward slope of the fore-arc high, a strike-slip fault zone is imaged (termed West Andaman Fault - WAF - in accordance with previous studies), is readily interpreted as the product of...

Daerah Selat Sunda yang merupakan daerah transisi antara zona subduksi frontal di selatan Jawa da... more Daerah Selat Sunda yang merupakan daerah transisi antara zona subduksi frontal di selatan Jawa dan subduksi miring di Sumatra memiliki karakter yang unik, antara lain ditandai dengan hilangnya cekungan busur muka dan terbentuknya struktur horst dan graben . Interpretasi struktur geologi dengan menggunakan data seismik refleksi yang diakuisisi oleh industri dan institusi riset, diintegrasikan dengan data batimetri menjelaskan dinamika geologi daerah busur muka Selat Sunda. Komplek prisma akresi, yang merupakan penerusan dari zona akresi Sumatra tersusun atas endapan cekungan busur muka yang terlipat dan tersesarkan. Sesar-sesar yang relatif lebih muda terbentuk di daerah yang sebelumnya merupakan bagian dari tinggian di daerah busur muka dan cekungan busur muka. Struktur-struktur yang berkembang di bagian horst dan graben tidak hanya berhubungan dengan sistem pull-apart , tetapi juga terkait dengan aktifitas volkanik-magmatik.

In Eastern Indonesia, the western Outer Banda arc accommodates a part of the oblique Australian m... more In Eastern Indonesia, the western Outer Banda arc accommodates a part of the oblique Australian margin collision with Eurasia along the Timor Trough. Yet, unlike the Wetar and Alor thrusts of the Inner Banda arc in the north and the adjacent Java subduction zone in the west, both recent and historical seismicity along the Timor Trough are extremely low. This long-term seismic quiescence questions whether the Banda Arc collision front along the Timor Trough is actually fully locked or simply aseismic and raises major concerns on the possible occurrence of large magnitude and tsunamigenic earthquakes in this vulnerable and densely populated region. Here, we jointly analyze multibeam bathymetry and 2D seismic reflection data acquired along the Timor Trough to characterize the location, nature, and geometry of active faults. Discontinuous narrow folds forming a young accretionary prism at the base of the Timor wedge and spatially correlated outcropping normal faults on the bending north...

Proceedings of the 7th Unconventional Resources Technology Conference, 2019

1Introduction Based on a previous 2D seismic survey in offshore Sierra Leone and Liberia revealin... more 1Introduction Based on a previous 2D seismic survey in offshore Sierra Leone and Liberia revealing the exploration potential of the margin, a 3D long offset survey in deep water Sierra Leone was acquired in 2008. Only two exploratory wells were drilled in offshore Sierra Leone in shallow water in 1982 (Mobil A-1) and 1985 (Amoco A1-2), but they still provide information of petroleum systems (rich source rock, reservoir quality sands, presence of seal). Additionally, significant field analogues exist in other basins of the Gulf of Guinea (e.g. Cote d’Ivoire, Ghana). Across the region, Aptian to early Cenomanian sequences contain rich, oil-prone to mixed oil and gas-prone Type II or III source rock. In the Sierra Leone basin, the late Cretaceous interval thickens to more than 2000m and most likely includes mature Cenomanian to Turonian source beds, established as Type II throughout offshore West Africa. This study assesses the prospectivity of block SL-5 by interpreting approximately ...

Proc. Indonesian Petroleum Association, IPA12-G-074, 2012

A new methodology for basin temperature modelling has been developed that utilizes large volumes ... more A new methodology for basin temperature modelling has been developed that utilizes large volumes (~10,000 points) of properly indexed and QC’d bottom-hole temperature (BHT) data for an onshore basin or area. This methodology honors the observation that borehole temperatures equilibrate, increasing towards formation temperature with elapsed time since fluid circulation. We thus use the maximum BHTs recorded in a layer (normalized for depth) or cell, rather than a corrected average or regression based model. Two main models have been developed to construct a present day temperature volume (cube): MaxG and MaxBHT. In the MaxG cube, we first define a depth varying interval geothermal gradient (IGG) function that models the maximum envelope of the BHT cloud for each major lithostratigraphic unit. If there is significant erosion in the basin, then the IGG used is adjusted for the maximum burial conditions. The MaxG cube is constructed by stacking the IGG calculated temperatures for all th...

This multidisciplinary study describes the burial and exhumation history of the frontier Galilee ... more This multidisciplinary study describes the burial and exhumation history of the frontier Galilee Basin in central Queensland, Australia, with implications for understanding its geohistory and unconventional gas prospectivity. Seismic interpretation, stratigraphic mapping, and an analysis of exhumation through quantifying overcompaction show total subsidence of approximately 2 km (∼6600 ft) from the Carboniferous to the Late Cretaceous, punctuated by two major exhumation events. Triassic exhumation was less than 600 m (<1970 ft), whereas Late Cretaceous exhumation was in the order of 1000 m (3300 ft), increasing eastward to greater than 1600 m (5250 ft). Geohistory reconstructions show that Permian coal measures generated up to 45 m3/t (1590 ft3/t) of gas when modeled temperatures exceeded 100°C (210°F) during maximum burial of 1.5–2 km (4920–6560 ft) in the Late Cretaceous. In the Carboniferous to the mid-Cretaceous, the basin was situated to the west of the Eastern Australian su...

Proceedings, Deepwater and Frontier Exploration in Asia & Australasia Symposium

The Mannar Basin lies between south-western Sri Lanka and the Indian coastline, in water depths r... more The Mannar Basin lies between south-western Sri Lanka and the Indian coastline, in water depths ranging from 50–3000m. Seismic data indicates that this is a failed rift basin containing over 5 seconds of inferred Late Jurassic–Early Cretaceous to Recent sediments constituting four discrete tectono-stratigraphic packages. The postulated petroleum system comprises: • Source – late Jurassic lacustrine or marginal marine shale and coal; early Cretaceous marginal marine or marine shale and coal. • Reservoir – late Cretaceous marine sandstones, Tertiary turbidites. • Seal – Paleocene regional shale or intraformational shale. • Trap – basement-related horst and tilted fault blocks within the synrift and rift and sag megasequences; Neogene compressional structures; three major periods of Cenozoic basin-floor and slope fan deposition provide stacked fan floor and slope deposits up to 1.0 second (TWT) thick and represent a major stratigraphic fairway in an apron of sediments tracking along th...

Geochemistry Geophysics Geosystems

We present the interpretation of newly acquired high-quality industry-standard deep seismic refle... more We present the interpretation of newly acquired high-quality industry-standard deep seismic reflection and swath bathymetry data to provide insight into the structural style and evolution of the Mentawai Fault Zone (MFZ). The MFZ lies along the boundary between the accretionary wedge and the proposed continental backstop. This zone exhibits arcuate ridges on the seafloor, convex toward the east. Beneath these ridges the structures developed as landward-vergent imbricated backthrusts in the inner part of the accretionary wedge and higher-angle backthrusts that deformed the forearc basin sediments. In the forearc high, anticlines were developed due to the seaward-vergent forearc high thrusts originating in the accretionary wedge. The imbricated backthrusts may have initiated during the Early-Middle Miocene contemporaneously with the slide and back-rotation of forearc high thrusts. In the Late Miocene, the higher-angle backthrusts were initiated. Continuous contraction induced the fron...

… Petroleum Association 35th …, 2011

Proc. Indon Petrol. Assoc., 35th Ann. Conv.

Proc. Indonesian petrol. Assoc., 38th Ann. Conv.