Deep Water Domain Research Articles

Crustal structures and salt tectonics on the margins of the western Algerian Basin (Mediterranean Region)

We present an overview of the crustal architecture of the continental margins of the oceanic Algerian Basin in the westernmost Mediterranean Sea. During the Cenozoic, and with a variable oblique convergence between the African and Eurasian plates, the Western Mediterranean Sea has experienced thinning and extension behind a tight orogenic arc formed by the Betics, Rif, and Tell Cordilleras. This study is focused on the structural style affecting the Messinian salt layer, which is mostly restricted to the deep domains of the Algerian Basin, where it is floored by a thin oceanic crust of probable Miocene age.Using deep-penetrating seismic profiles and wells from offshore western Algeria to southeastern Spain, we have analyzed the crustal structures affecting the domains close to the oceanic-continent transition on the three margins of the western Algerian Basin. Since the Early Miocene, active shortening in the Tell-Atlas domain has accommodated most of the plate convergence in the basin, whereas the Alboran margin in the west and the Iberian margin in the north experienced eastward and southward crustal extension and thinning, respectively, accompanied by volcanism. The Algerian margin in the south shows incipient thrusting of African continental crust over oceanic crust. This shortening occurred since at least the Late Miocene, also promoting decoupling and contraction of the deep, sub-horizontal Messinian salt layer. The salt exhibits diapir squeezing and suprasalt folding, whereas the presalt sequence preserves partially-inverted half-grabens. Salt tectonic processes along the northern and western margins of the Western Mediterranean Basin show contrasting structural styles formed by narrow extensional and transtensional domains with gentle salt anticlines.This region shows therefore a somewhat unusual salt-tectonic style, departing from the gravity-driven model typical of continental margins that contain an initial continuous, gently-dipping salt layer. In the Algerian Basin, salt is mostly restricted to deep water domain floored by oceanic crust, so it does not participate in significant gravity-driven deformation. Instead, Messinian salt and the suprasalt sequences underwent significant shortening along the southern margin, simultaneous with thick-skinned extension involving the Messinian evaporites in the northern and eastern margins.

Origin and preservation conditions of organic matter in the Mozambique Channel: Evidence for widespread oxidation processes in the deep-water domains

The Mozambique and Madagascar margins present major rivers that are responsible for the discharge of large amounts of terrestrial organic matter (OM) which can influence carbon cycling in marine environments. Therefore, the Mozambique channel represents a unique case to study the fate of the organic carbon in deep-water domains. Using a new and extensive data set of sedimentary OM collected from sediment traps, seafloor sediments and core sediments, we address the origin of the OM that is transported and deposited in the Mozambique Channel, its degradation state and preservation conditions. A Rock-Eval 6 survey allowed us to characterize the origin and amount of OM from shallow to deep-water turbidite systems, between 500 and 4400 m water depth. Rock-Eval 6 performed on suspended sediments within particle traps at 47 m above the seabed show that the OM is transported into the deep-water domain with relatively high TOC (between 1.5 and 2.5%). However, the OM is largely oxidized close to the water-sediment interface (Oxygen Index >300 mg CO2/g TOC). Seafloor sediments sampled to a maximum depth of 40 cm show lower TOC values compared to those collected from particle traps suggesting that the degradation of the OM is mainly active at the water-sediment interface. Small concentrations of OM are preserved within the recent sediments of the distal area of the Zambezi turbidite system below 2500 m water depth (TOC < 0.5%). Rock-Eval results show that core sediments from the Majunga slope (NW margin of Madagascar) and the Zambezi slope (Mozambique margin) contain the highest concentration of terrestrial OM (TOC between 1 and 2%). However, the OM within core sediments from the deep-water domain is largely oxidized and degraded, probably due to the conjugate effect of low sediment accumulation rates (SARs) and high permeabilities of the coarse-grained sediments. Consequently, the deep-water domain of the Mozambique Channel does not seem to be an important sink of terrestrial OM. This process is reinforced by important bottom water currents which induce the remobilization and transport of seafloor sediments that lead to higher oxygen exposure time in the uppermost centimeters of sediments.

Low cost underwater acoustic localization

Over the course of the last decade, the cost of marine robotic platforms has significantly decreased. In part this has lowered the barriers to entry of exploring and monitoring larger areas of the earth's oceans. However, these advances have been mostly focused on autonomous surface vehicles (ASVs) or shallow water autonomous underwater vehicles (AUVs). One of the main drivers for high cost in the deep water domain is the challenge of localizing such vehicles using acoustics. Here we propose a novel low cost underwater modem design to assist in localizing deep water submersibles. The system will consist of location aware anchor buoys at the surface and underwater nodes. We present a comparison of methods, simulation of the proposed algorithms as well as experimental results, together with details on the physical implementation to allow its integration into a novel deep sea AUV currently in development.

The structure of the mesoplankton community in the area of the continental slope of the St. Anna Trough (Kara Sea)

Zooplankton samples and concomitant hydrophysical data have been obtained in the outer Kara shelf over the continental slope and adjacent deepwater region of the western spur of the St. Anna Trough in the last ten days of September in 2007 and 2011. Mesoplankton biomass in the examined regions in 2007, the warmest year of the last three decades, was 1.5–2 times higher than the relatively cold year of 2011. A frontal zone, distinct in temperature, salinity, and chlorophyll fluorescence in the surface sea layer was located over the continental slope. The temperature gradient in the frontal zone reached 0.25–0.67°C/km, and its salinity gradient reached 1.6–4.7 psu/km. An increase in mesoplankton biomass was associated with the frontal zone, which was especially pronounced in the upper layers of the water column. The average biomass content in the upper 50 m in the frontal maximum amounted to 1210 mg/m3 in 2007 and 972 mg/m3 in 2011, being two orders of magnitude higher than the outer shelf and the deepwater domain of the basin. The pteropod Limacina helicina was dominant at the slope maximum, accounting for up to 80% of mesoplankton biomass. The frontal zone over the slope also represented a distinct boundary separating the shelf mesoplankton community from the deepwater community, which drastically differed in composition and biomass.

Reply to Chang et al., 2014, Evolution of the South China Sea: Revised ages for breakup and seafloor spreading

Chang et al. introduce some new lines of evidence for an end of seafloor spreading in the South China Sea not before 15 Ma. However, we find strong indications that their interpretation is not conclusive. The origin of the East Taiwan Ophiolite from the SCS as assumed by Chang et al. is not in agreement with recent studies which find continental crust in the deep-water domain of the northeastern South China Sea. The age dating of the East Taiwan Ophiolite is based on one single K–Ar age of questionable accuracy. The calculation of Te-derived ages leaves a thermal rejuvenation of the oceanic crust in the South China Sea by post-spreading volcanism out of consideration. Biostratigraphically determined ages of sediments recovered directly above igneous crust of the South China Sea during IODP 349 drilling expedition are inconclusive so far. The final key to unlocking the spreading history of the SCS will be the Ar–Ar age dating of the basaltic rocks recovered during IODP Expedition 349.

En Route: The Production Capacity Challenge

President's column Peak Oil Theory has been a subject of intense discussion since it was established by M. King Hubbert in the 1950s. The theory basically states that production is limited by resources—i.e., geology. I believe that, although it will be a reality one day, the theory is not correct globally for the short and mid term. But I also believe that we are in fact facing another limitation, one caused by production capacity. For conventional hydrocarbons, explorationists have literally invented new domains for seeking oil and gas, and this has proven to be very efficient. A good example is the deepwater domain (now subsalt), which has added a large amount of reserves in various parts of the world and will certainly continue to do so for a while. The Hubbert decline curve, which historically has been a good fit with the production of the US Lower 48 states, is no longer applicable because of this domain extension; it works for a given domain. We have produced most of the conventional hydrocarbons—these have been easy to produce, but in relatively small volumes. As illustrated by the resource triangle (Fig. 1), a concept invented by Steve Holditch, there are huge resources in unconventional hydrocarbons in both oil and gas but they are difficult to produce. Interestingly, the production from these resources is also difficult to predict. Look at the booming activity and production of shale gas in North America, for example; very few forecasts, if any, were anticipating that boom 10 years ago or even less. The resources are abundant. The challenge we face comes from production capacity. I will illustrate what I am talking about with oil, but the situation is similar for gas. On one side, we will have a slight increase in demand—1% to 1.5% per year, according to the International Energy Agency’s “reference scenario.” On the other side, our producing fields are ageing, and will decline at a rate of about 5% per year. As a consequence, the gap between demand and production from existing fields will widen, to be filled by new production. These figures illustrate this challenge: 2009 production was about 85 million BOPD. 2019 demand will be about 95 million BOPD. Taking into account the decline of existing fields, to go from 85 to 95 million BPOD we must add not 10 million BOPD production capacity, but about 45 million BOPD of new production. That represents half of today’s production. This is an enormous challenge—the production capacity challenge. Huge efforts will be needed. To be successful will require technology, innovation, capital, and staff.

A Survey of Ocean Simulation and Rendering Techniques in Computer Graphics

Abstract This paper presents a survey of ocean simulation and rendering methods in computer graphics. To model and animate the ocean’s surface, these methods mainly rely on two main approaches: on the one hand, those which approximate ocean dynamics with parametric, spectral or hybrid models and use empirical laws from oceanographic research. We will see that this type of methods essentially allows the simulation of ocean scenes in the deep water domain, without breaking waves. On the other hand, physically‐based methods use Navier–Stokes equations to represent breaking waves and more generally ocean surface near the shore. We also describe ocean rendering methods in computer graphics, with a special interest in the simulation of phenomena such as foam and spray, and light’s interaction with the ocean surface.

Hydrocarbon-bearing areas in the eastern part of the Ukrainian Black Sea

The eastern part of the Ukrainian Black Sea consists of the Kerch Shelf with water depth less than 100 m that covers an area of 5500 km2. To the SE of the Crimean Peninsula, the much larger deepwater domain (about 40,000 km2) has a maximum water depth of about 2200 m (Figure 1). The main tectonic units of the deepwater domain are as follows: the easternmost part of the Western Black Sea Depression, the northwestern part of the Eastern Black Sea Depression, the South Crimean Cenozoic Orogen, the Tetyaev-Shatsky and Andrusov ridges, and the Sorokin Trough. All of these tectonic units were formed from the middle Mesozoic until the present day.

Structure sismique de la plate-forme Atlantique au large d'Agadir (Maroc sud-occidental)

Offshore seismic reflection and well data have been used to establish the structural style of the offshore of Agadir and to extend the Atlas fabric into the deep-water domain. The obtained structural subsurface map exhibits a complex architecture resulting from the coexistence of normal, inverse, wrench faults and folds cored by Triassic salt. The seismic data indicate a structural style characterised by narrow, detached folding above Triassic salt layers. The strong similarities in the style of deformation between the Agadir offshore and the Cap-Tafelney fold belt, suggest that both of them form one continuous belt, which corresponds to the western termination of the Atlas alpine system.

Petróleo na margem continental brasileira: geologia, exploração, resultados e perspectivas

O conceito de sistema petrolífero agrupa os diversos elementos que controlam a existência de jazidas de petróleo numa bacia sedimentar. Tal conceito, visualizado numa escala global, parece justificar de maneira adequada as diversas províncias petrolíferas conhecidas. A evolução tectono-sedimentar meso-cenozóica da margem continental brasileira propiciou o desenvolvimento desses elementos-chave, cuja presença é requisito fundamental a que uma determinada região seja atrativa para a prospecção petrolífera. Merece destaque nesse particular o segmento de águas profundas da Bacia de Campos, que, na visão contemporânea, representa a porção mais bem aquinhoada em termos de volumes descobertos de toda a margem brasileira. Em termos históricos, a exploração de petróleo no Brasil inclui três grandes fases: o período pré-Petrobras, basicamente de atividades pioneiras de reconhecimento; a etapa de exclusividade da Petrobras, onde se vislumbram quatro etapas - 1954/1968: Fase Terrestre, 1969/1974: Fase Marítima/Plataforma Rasa, 1975/1984: Fase Marítima/Plataforma Rasa/Bacia de Campos, e 1985/1997: Fase Marítima/Bacia de Campos/Águas Profundas, cada uma delas com características particulares e responsável por sucessivos incrementos na reserva petrolífera do País, que alcança hoje cerca de 16 bilhões de barris de óleo-equivalente; e a fase atual, sob a vigência da Nova Lei do Petróleo, caracterizada por intensa atividade em que várias companhias nacionais e estrangeiras atuam tanto em áreas anteriormente trabalhadas como em desafiadoras novas fronteiras.

Evolution and Hydrocarbon Potential of Offshore Pinar del Rio Area, Southern Gulf of Mexico: ABSTRACT

ABSTRACT The evolution of Southeast Gulf of Mexico comprises three main periods: pre-orogenic, syn-orogenic and post-orogenic. During pre-orogenic time, from Lower Jurassic to Campanian, the stages are the rift of Pangaea and the thermal subsidence (or drift). In drift stage two domains interacted in the space; the carbonate platforms (Bahamas, Yucatan, Organos and others) and the deep water basins. These fluctuations were dictated by the differential subsidence and horizontal displacements of basement blocks as well as by the eustatic movements of the ocean. The Organos platform, for example, was entirely submerged since Upper Jurassic and sedimentation continued in a deep water environment. The collision between Greater Antilles Volcanic Arc and the continental margins has modeled the Cuban orogen since the Upper Cretaceous. Here, the southern facies was thrusted over the northern section with simultaneous strike slip movements. The interaction suddenly ceased in the Eocene. The source rock levels are considerably more frequent in the deep water domain than in the platforms. The Lower and Upper Jurassic as well as the Lower and Middle Cretaceous horizons have a very high content of organic matter. The offshore seismic profile shows the transition from the thrusted belt to the foreland basin with a typical triangle zone configuration. Reservoirs are expected in the Cretaceous section and are covered by seals formed of early foreland basin sediments of Upper Cretaceous-Paleocene age. Foothill structures have a great potential for hydrocarbon exploration. End_of_Record - Last_Page 483-------