Depositional environments in areas located near sea level are vulnerable to even subtle changes in both tectonism, climate and eustatic sea level. Sorting out mechanisms behind depositional changes in inner shelf-margins and epeiric seas is therefore far from straight forward. The epeiric Malay-Tho Chu Basin, located in the shallow Gulf of Thailand offshore Vietnam, contains a thick uppermost Oligocene to Recent post-rift succession. Based on 18000 km of 2D seismic profiles, the uppermost Oligocene-Recent succession is subdivided into six seismic sequences. Seismic facies mapping of each sequence complemented by information from industry completion reports of 14 wells document a gradual increase in marine influence from latest Oligocene through Middle Miocene time. The increased marine influence reflects the propagation and opening of the southwestern spreading arm of the East Vietnam Sea (South China Sea (East Sea)) combined with rapid subsidence in the Malay-Tho Chu Basin resulting from fast thermal relaxation following Oligocene rifting and amplified by mild fault-controlled subsidence in especially the western part of the area. From the latest Middle Miocene, slowed subsidence and regression occurred in association with uplift in the nearby southwestern East Vietnam Sea. From the latest Miocene, and during the Pliocene and Pleistocene, subsidence rates increased promoting marine conditions towards the East Vietnam Sea in the southeast. Meanwhile, Mekong River avulsion combined with hinterland uplift stimulated fluvial and alluvial deposition in the northern and western parts of the basin. The long-term depositional pattern was controlled primarily by tectonics, drainage evolution and climate. Meanwhile, flood- and delta plain deposits intercalated with stacked fluvial incisions, often filled by estuarine deposits, document short-lived environmental changes most likely controlled by eustatic sea level fluctuations. Such intervals developed during latest Middle Miocene to Pleistocene periods of slow subsidence or fast depositional rates and are interpreted to be the result of substantial eustatic sea level fluctuations.
Continental extrusion may take up much of the deformation involved in continental collisions. Major strike-slip zones accommodate the relative extrusion displacement and transfer deformation away from the collision front. The Red River fault zone (RRFZ) accommodated left- and right-lateral displacements when Indochina and South China were extruded during the Indian-Eurasian collision. The northern Song Hong basin onshore and offshore in the Gulf of Tonkin delineates the direct extension of the RRFZ and thus records detailed information on the collision-induced continental extrusion. We assess the rapidly evolving kinematics of the fault zone buried within the basin based on seismic analysis. Contrary to previous studies, we do not identify indications for latest Miocene left-lateral motion across the RRFZ. We tentatively consider the shift from left- to right-lateral motion to have occurred already during the middle Late Miocene as indicated by inversion of NE-SW-striking faults in the Bach Long Vi area. Right-lateral displacement terminated around the end of the Miocene in the Song Hong basin. However, continued inversion in the Bach Long Vi area and NNW-SSE-striking normal faulting suggests a stress regime compatible with right-lateral motion across the onshore part of the RRFZ continuing to the present. Inversion around the Bach Long Vi Island may have accommodated up to a few kilometers of right-lateral displacement between the Indochina and South China blocks. Comparable NE-SW-striking fault zones onshore may have accommodated a larger fraction of the right-lateral slip across the RRFZ, thus accounting for the restricted transfer of lateral displacement to the offshore basins.
This reference is for an abstract only. A full paper was not submitted for this conference. Abstract Neogene carbonate platforms cover as much as 70,000 km2 of the central Vietnamese South China Sea margin. The margin is little explored, and so far, exploration has focussed on Miocene carbonates with a number of oil and gas discoveries made. Carbonate growth initiated during the Early Miocene following Eocene-Oligocene continental rifting. Early carbonate deposition took place on two regional platforms separated by a narrow depression that marks the trail of the East Vietnamese Boundary Fault Zone (EVBFZ). West of the EVBFZ, the Tuy Hoa Carbonate Platform fringes the Vietnamese margin between Da Nang and Nha Trang. In the west, platform growth initiated during the Early Miocene and continued until Middle Miocene time when regional uplift along the Vietnamese margin led to sub-aerial exposure and karstification. Seawards from the EVBFZ, carbonate deposition similarly commenced during Early Miocene time (Burdigalian). Platform growth took place on the Qui Nhon Ridge flanking the EVBFZ and farther seawards on the Triton Ridge. From the latest Early Miocene, stepwise partial drowning resulted in platform split-up and seaward retreat of carbonate growth. Hemipelagic drapes cap drowned platforms and indicate protracted periods of sediment starvation after drowning. Continued drowning is evidenced by platforms subcropping the present seafloor at few hundred meters depth, and modern platform growth only remains on a number of seafloor cuestas around the Paracel Islands far from the Vietnamese mainland. The onset of widespread carbonate deposition largely reflects the opening of the South China Sea. The mid-Neogene shift in carbonate deposition is interpreted as a consequence of regional uplift of central and south Indochina starting around Middle Miocene time when the Qui Nhon Carbonate Platform became sub-aerially exposed. Stressed carbonate growth resulted from increased inorganic nutrient input derived from the uplifted mainland, which promoted platform drowning farther offshore.
Summary The Phu Khanh basin is a rifted continental margin formed by Paleogen rifting and subsequent post-rift subsidence. The basin is situated along the narrowest part of the Bien Dong Sea's shelf and is characterized by a water depth ranging from a few tens of meters to abyssal depths towards the east. The Carbonates growth initiated during the late Early Miocene along the open marine Vietnamese margin and continued throughout to late Miocene. During this period, the structural grain, tectonic conditions as well as oceanographic e¡ects exerted major controls on carbonate deposition. The Carbonate Platform located in the South-western part of the Phu Khanh Basin is one of the largest carbonate platforms in the South China Sea while Carbonate Built-up within the Early-Mid Miocene sequences are considered the most prospective reservoir of the Phu Khanh Basin. In addition, the other type of Carbonate - reefs may be present in the deep waters of Phu Khanh form important targets for petroleum exploration. The purpose of this paper is to present the Carbonates Characterzation and its Evolution during the post-rift period in the Phu Khanh Basin.
Abstract The East Greenland Prograded Margin and Oceanic Composite Tectono-Sedimentary Element (EGPMO CTSE) consists of the East Greenland Prograded Margin Tectonic-Sedimentary Element (TSE) and the East Greenland Oceanic (EGO) TSE located over continental and oceanic crust, respectively. The East Greenland Prograded Margin TSE (EGPM TSE) is made up of six segments, with their basal part deferring from Maastrichtian to Miocene in age. The variation reflects the different timing in transition from syn- to post-rift, controlled by the lateral migration of rifting and diachronic continental break-up in the northern North Atlantic. The post-rift history can be subdivided into a pre-break-up Maastrichtian–Paleocene post-rift phase developed entirely offshore NE Greenland and an earliest Eocene–Miocene syn- to post-break-up phase developed in the wake of progressive continental rupture. Finally, the CTSE started to develop as a unified body from Miocene time after the complete separation of Greenland from Eurasia and the Jan Mayen microcontinent. The EGO TSE has formed since the earliest Eocene commencement of seafloor spreading. The structural and depositional outline of the EGPMO CTSE depicts its tectonic history but also reflects phases of volcanism, denudation and intensified icehouse conditions since the middle Miocene that were triggered by the opening of the Fram Strait and the uplift of East Greenland. The first major northern hemisphere glaciations started in NE Greenland. Glaciations expanded southwards during the late Miocene as the Denmark Strait was transgressed and cold surface water from the high arctic started flowing along SE Greenland, cooling the region. The petroleum potential of the EGPM TSE is conceivably modest but a potential exists locally offshore northern NE Greenland where hydrocarbons sourced mainly from the Jurassic–Cretaceous section may have charged structures cored by Maastrichtian–Eocene sandstone reservoirs sealed by overlying marine mudstones.
Abstract Evaluation of the regional geotectonic impact of the High Arctic Large Igneous Province (HALIP) in the present‐day northern Atlantic region has been hindered by poor correlation between the Svalbard–Barents Shelf region and eastern North Greenland. New sedimentological and biostratigraphic data from Peary Land and Kronprins Christian Land (Kilen), North Greenland reveal that the Lower Cretaceous palaeogeographic and sequence stratigraphic development of this area is closely comparable to that of Svalbard. The succession records Hauterivian – early Barremian regional uplift and emergence followed by fluvial sedimentation and subsequent transgression in the late Barremian – early Aptian. Recognition of this tectonically forced regression in North Greenland provides a link to a coeval well‐known tectonostratigraphic event in the Svalbard region, and hence to regional tectono‐magmatic uplift heralding the HALIP and the initiation of the Amerasia Basin.
A series of Cenozoic basins fringes the Vietnamese coastal margin, often characterised by more than 10 km of sedimentary infill (Fig. 1). Greater parts of the margin are still in an early explorational state, although significant petroleum production has taken place in all but the southern Song Hong and the Phu Khanh Basins. This has increased the need for a fundamental understanding of the processes behind the formation of the basins, including analyses of potential source rocks. The basins fringing the Indochina Block provide excellent evidence of the geological evolution of the region, and the basin geometries reflect the collision of India and Eurasia and the late Cenozoic uplift of south Indochina (Rangin et al. 1995a; Fyhn et al. in press). In addition, the basins provide evidence of regional Palaeogene rifting and subsequent Late Palaeogene through Early Neogene sea-floor spreading in the South China Sea. Apart from the regional Cenozoic tectonic record, the basins contain a high-resolution climatic record of South-East Asia due to the high depositional rates, changing depositional styles and large hinterland of the basin (Clift et al. 2004).
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