Canyon Fill Research Articles

Evolution and architecture of an exhumed ocean‐facing coarse‐grained submarine canyon fill, Baja California, Mexico

Evolution and architecture of an exhumed ocean‐facing coarse‐grained submarine canyon fill, Baja California, Mexico

Właściwości fizyczne zbiorników łupkowo-piaskowych: Pole Szafranowe, Delta Nilu, Egipt

The Saffron gas Field is in the Scarab-Saffron Development Lease in the offshore Nile Delta. It was discovered by the Saffron-1 exploration well drilled in 1998 and appraised by Saffron-2 and Sapphire-3 wells. Saffron is a stacked channel system and consists of 6 different reservoirs with differing levels of connectivity between them. It can be interpreted as deep-water canyon fill deposits on a delta-front slope. Some physical properties of 4 full diameter core samples (approximatly164 core plugs) obtained from the Saffron-2 borehole were petrophysically analysed. Helium porosity, horizontal and vertical permeability, grain density and electrical resistivity were laboratory measured. Several bivariant plots were accomplished such as porosity- permeability; grain density, formation resistivity factor; cementation exponent and Winsaur’s multiplier (a) as well. Several regression line equations with robust coefficient of correlations were obtained to be used for reservoir characterization. On the other hand, numerous frequency histograms were built for most of the measured reservoir parameters to determine their type of distribution and other statistical parameters. Some important relations like cementation exponent versus multiplier (a) are performed which improves Archie’s general equation and subsequently the reservoir fluid saturation (Sw and/or Sh). The lack of stratification in sedimentary section represented by core numbers 4&5 of Saffron-2 well have severe consequences on measured reservoir parameters especially exposed by the porosity- permeability relation.

Gravity tectonics controls on reservoir-scale sandbodies: Insights from 3D seismic geomorphology of the canyons buried in the upper slope of the Eastern Niger delta basin

High-resolution 3D seismic data analysis was integrated with a calibrated well and biostratigraphy data to present the first overview of a buried Pleistocene canyon system on the upper slope of the eastern Niger Delta, the Galabor Canyon. Attribute maps of specific horizons allow documenting the changing morphologies and infill lithologies of two main branches of the canyon through two stages of activity separated by a reference horizon dated at 0.99 Ma based on well calibration. At the upper slope, growth faults dissect the canyon heads, the catchment of which encroaches a network of valleys incised on the outer shelf. The canyon fill is composed of muddy channels and mass-transport deposits, largely derived from the collapse of canyon walls and sand-rich bodies forming a tract sourced by shelf-edge deltas at the outlet of the incised valleys. High-density turbiditic processes likely control the distribution of sand bodies along the canyon, ranging from tributary fans on the upper slope to 6 km-wide meander belts on the middle slope. The sandy deposits accumulate in minibasins formed along the canyon path, downstream of the subsiding hanging wall of the growth faults and upstream of shale ridges that damp the flow in the canyon. These results show that canyons can be major targets for sand reservoir exploration on the upper slope of large muddy deltas.

Late Quaternary fluvial environments at Abo Arroyo, New Mexico, U.S.A.: response to millennial-scale climate change

ABSTRACT Abo Arroyo is a tributary of the Rio Grande in central New Mexico. Its alluvial sequence is made up of four informal units, their age defined by 44 AMS radiocarbon dates from 12.8 ka to 0.85 ka. The earliest, unit 1, is terminal Pleistocene to early Holocene (12.8 ka to 9.0 ka), including the Scholle wet meadow (12.3 ka to 11.1 ka) related to the Younger Dryas. After an erosional gap in the record from 9 ka to 6 ka, coarse gravel (unit 2) was deposited in the channel (5.8 ka and 4.3 ka) during the middle Holocene period of aridity. Subsequently, the late Holocene wet period is characterized by fine-textured alluvium (unit 3) (3.5 ka to 0.945 ka) with shells of an aquatic snail, indicating persistent stream flow. An upper 2-m zone of dark-colored clayey silt beds with high amounts of organic carbon and carbonate accumulated from 1.7 ka to 0.945 ka. A record of C4 signatures, previously interpreted to indicate dry conditions 1.4 ka to 0.945 ka, is reinterpreted as an interval of exceptionally wet floodplain conditions with C4 grasses and sedges. Abo Arroyo and other studies indicate three major episodes of late-Quaternary channel entrenchment: 1) from the full-glacial to late glacial-Bølling/Allerød (6.1 ky), 2) during the middle Holocene (2.5 ky), and 3) during the late Holocene Medieval Warm Period (0.4 ky), each erosional event less severe and shorter duration than the preceding one, and all three represent a significant change from wet to dry climate. During the Medieval Warm Period (A.D. 900 to 1300), a shallow channel formed in unit 3 alluvium, bracketed by AMS dates A.D. 1005 in unit 3 alluvium and A. D. 1100 in unit 4 channel fill. The channel cutting occurred with the shift from wet to dry climate, although the downcutting event was preceded by 100 years of landscape adjustment to the long drought. The canyon fill was entrenched again, deep and wide, by arroyo cutting in the late nineteenth and early twentieth centuries. The regional 83-year second-century drought (A.D. 100 to A.D. 182), documented by tree rings, shows up in the stable-carbon-isotope record from Abo Arroyo alluvium. The drought was more severe than the 400-year warm period but had little effect on the preserved alluvial record. The less severe but longer-duration Medieval Warm Period resulted in channel cutting at Abo Arroyo and elsewhere in the broad region at that time, but the second-century drought did not. Finally, the similarity of Abo Arroyo and Rio Grande late Holocene alluvial records with parallel stratigraphy, sedimentology, and geochronology illustrates that tributaries and main valleys respond alike and in concert to climate and climate change.

Deep-water Tectono-Stratigraphy at a Plate Boundary Constrained by Large N-Detrital Zircon and Micropaleontological Approaches: Peninsular Ranges Forearc, Baja California, Mexico

The distribution of sedimentary systems on Earth’s surface is intimately linked to tectonics, therefore, at plate boundaries the stratigraphic archive can unlock the timing and style of tectonism and relative plate motions. Using large-n detrital zircon and micropaleontological analyses, tied to field mapping and data collection, we unravel the timing of strike-slip motion and its influence on the development of a Cretaceous submarine canyon on a long-lived oblique-convergent margin. Structural analysis demonstrates that the canyon bedrock, composed of fluvial rocks (La Bocana Roja Fm., of maximum depositional age (MDA): 93.6±1.1 Ma), underwent both syn- and post-depositional contractional and extensional deformation during the Cenomanian-Turonian in response to dextral strike-slip movement. Relative sea-level rise associated with basin subsidence and hinterland uplift was coincident with incision and fill of a submarine canyon system (Punta Baja Fm., MDA 87.1±1.5 Ma to 84.9±2.0 Ma), which exploited structural lineaments in the bedrock. The canyon was filled by sediment derived from an uplifted magmatic arc during the Coniacian to Santonian, most likely shed from erosional topography associated with plutonic intrusions to the NE. Structural data suggest that oblique dextral strike-slip motion on the Pacific margin controlled the development and location of submarine erosion, and had ended by the earliest Santonian, significantly earlier than previously estimated. Basinward tilting led to uplift, followed by transgression and wave ravinement of the canyon fill, which was then overlain by a shallow-marine to fluvial system. Thus, the canyon was cut, filled, buried, uplifted and rotated basinward, planed off through wave ravinement, and onlapped by shallow-marine to fluvial sediments within an 8 Myr period. Our findings, in part, reconcile contrasting basin evolution models for the Late Mesozoic Pacific margin.

Evolution of a Miocene canyon and its carbonate fill in the pre-evaporitic eastern Mediterranean

Extensive canyons, excavated into the margins of the Levant Basin during the Oligocene–Miocene, are interesting case-studies for canyon fills in carbonate settings. The carbonate Pattish Formation, developed along the margins of the pre-evaporitic Messinian Beer Sheva Canyon in Israel, was investigated using both onshore seismic imaging and field data. The canyon has three main seismic facies of fill (1) Subparallel reflections mimicking the canyon´s morphology; (2) chaotic reflections overlying the subparallel ones, and (3) sigmoidal reflections, locally with sharp edges at the canyon margins. The first seismic facies corresponds to the pelagic marls of the Bet Eshel Formation. The other two seismic facies are, respectively, equivalent to bioclastic calcarenite clinobeds with slumps and channels, and to coral–stromatolite reefs and reef slopes of the Pattish Formation observed at outcrop. There were three phases of canyon development: (1) slope incision and headward erosion due to tectonic uplift and eustatic sea-level fall during the Early Oligocene, and large slope failure during the latest Middle Miocene; (2) platform incision and connection with a fluvial system in the Late Miocene related to falling sea level and tectonic uplift; and (3) canyon filling first by pelagic marls at the centre of the canyon, followed by calcarenite clinobeds at the canyon flanks formed by gravity flows. Finally, carbonate production at the margins of the canyon resulted in reefs and associated slopes prograding towards the canyon axis. The late canyon filling phase ended with the deposition of evaporites during the Messinian Salinity Crisis.

Architecture of coarse-grained gravity flow deposits in a structurally confined submarine canyon (late Eocene Tokaren Conglomerate, Slovakia)

This study documents the coarse-grained fill of an upper slope, late Eocene Tokaren Canyon in the Carpathian Mountains, whose planform geometry and internal architecture were driven by normal faulting of an underlying carbonate platform. Facies analysis hints at a narrow shelf and a direct link to rivers draining a rapidly-uplifting hinterland. The axial part of the canyon consists of several meters thick, amalgamated conglomerate intervals deposited by debris flows and, to a lesser extent, by debris falls, slides and high-density turbidity currents. The sediments form sheets consisting of several tens to several hundreds of meters wide lobes occasionally entrenched by small erosional chutes. The deposits on the higher, fault-bounded blocks closer to the channel margins, include well-developed conglomerate–sandstone packages. They show a sheet-like geometry scattered with small channels. The textural immaturity of the sediment, grain-size caliber, the sediment thickness variation in the canyon, the sedimentary facies and their spatial distribution imply a dominant role of tectonics and sediment supply in the evolution of the canyon.Despite numerous studies of canyons in tectonically active settings, there are surprisingly limited studies on the depositional fill architectures of such canyons based on outcrop analogs. The detailed study of the Tokaren Canyon architecture brings a valuable insight into processes and distribution of proximal canyon fill facies controlled by syn-depositional faulting. It describes the architecture of such coarse-grained depositional system fed directly by rivers and governed by tectonics and supplements the knowledge from such systems obtained by different methodologies.

Repeated degradation and progradation of a submarine slope over geological timescales

ABSTRACTSubmarine slopes prograde via accretion of sediment to clinoform foresets and degrade in response to channel or canyon incision or to mass-wasting processes. The timescales over which progradation and degradation occur, and the large-scale stratigraphic record of these processes, remain unclear due to poor age constraints in subsurface-based studies and areally limited exposures of exhumed systems. We here integrate 3D seismic reflection and borehole data to study the geometry and origin of ancient slope canyons developed in late Mesozoic strata of the Måløy Slope, offshore Norway. Slope degradation and canyon incision commenced during the late Kimmeridgian, coincident with the latter stages of rifting. Later periods of canyon formation occurred during the Aptian to Albian and the Albian to Cenomanian, during early post-rift subsidence. The canyons are straight, up to 700 m deep, and 10 km wide on the upper slope and die out downdip onto the lower slope. The canyons trend broadly perpendicular to and crosscut most of the rift-related normal faults, although syn-filling fault growth locally helped to preserve thicker canyon-fill successions. The headwalls of the oldest (late Kimmeridgian) canyons are located at a fault-controlled shelf edge, where younger canyons overstep this fault, which was inactive when they formed, extending across the paleo-shelf. Downslope, Aptian to Albian canyons either erode into the older, late Kimmeridgian to Barremian canyon fills, forming a complicated set of unconformities, or in the case of the Albian to Cenomanian canyons, die out into correlative conformities. Boreholes indicate that the canyon bases are defined by sharp, erosional surfaces, across which we observe an abrupt upward shift from shallow- to deep-marine facies (i.e., late Kimmeridgian canyons), or deep marine to deep marine facies (Aptian to Albian and Albian to Cenomanian canyons). Missing biostratigraphic zones indicate the canyons record relatively protracted periods (c. 2–17 Myr) of structurally enhanced slope degradation and sediment bypass, separated by > 10 Myr periods of deposition and slope accretion. The trigger for slope degradation is unclear, but it likely reflects basinward tilting of this tectonically active margin, enhanced by incision of the slope by erosive sediment gravity flows. The results of our study have implications for the timescales over which large-scale slope progradation and degradation may occur on other tectonically active slopes, and the complex geophysical and geological record of these processes. We also show that canyon formation can cause large volumes of margin-derived sediment to bypass proximal sub-basins within rifted terranes, an important process not currently captured by marine rift-basin tectono-stratigraphic models.

Meteora: a Billion Years of Geological History in Greece to Create a World Heritage Site

The rock pinnacles of the Meteora UNESCO World Heritage Site, Central Greece, are global geologic icons but are inadequately studied. Herein, we summarize decades of observations leading to a geohistory and geoenvironmental model of the unique conditions that were essential for their creation. Via this synthesis, we hope thus to encourage further specialized studies of the West Thessaly-Meteora region and to promote the value of updating geological research within World Heritage Sites. The Meteora rock spires owe their existence to ten critical geologic episodes spread over a period of nearly a billion years. Early Miocene sedimentary deposits that make up the rock spires are derived largely from the metamorphic core complex of the exhumed Pelagonian (~ Precambrian to Permian) continental complex and include fragments of “blueschist” derived from the Miocene exhumation of Mount Olympos (subducted Triassic-Eocene carbonate banks). The Miocene sediments are deposited as turbidite formations overlain by “Gilbert-style” deltaic conglomerates. The cobble-turbidite formations comprise submarine canyon fills. The rock spires themselves result from initiation of Pleistocene erosion into a peneplain estimated, very roughly, to ~ 700,000 years in age. This geoenvironment is similar to today’s active sedimentation ongoing off the Malibu coast of California in that the deposits include “Gilbert-style” deltas and turbidites originating from an exhuming metamorphic complex, simultaneously eroding and depositing within off-shore canyons. This comparative model requires a reinterpretation of the “consensus” interpretation of the Miocene oceanic margin south of the Meteora region to one hosting more active energetic deposition and a deeper basin.

Down-canyon evolution of turbidity currents at a late-glacial ice margin: Halibut Canyon, offshore southeastern Canada

Submarine canyons are the principal conduit for turbidity currents transporting sediment to the deep sea. This study examines the interplay between ice-margin conditions and the style of turbidity currents during deglaciation from 19 to 11 ka. We investigated 7 cores from Halibut Canyon, located seaward of a small ice stream draining the Newfoundland Ice Dome. Cores were X-radiographed for sedimentary structures, sediment provenance was assessed from X-ray fluorescence geochemistry, and age was determined by AMS C-14 dating. High resolution seismic profiles and cores show three phases of canyon evolution: (1) Canyon erosion by plunging hyperpycnal meltwater from shelf-edge ice at maximum ice extent. (2) During deglaciation, active deposition of an inner levee by turbidity currents, adjacent to an erosional talweg system, recorded in cores from the Younger Dryas (12 ka) to before H1 (16.5 ka). (3) Passive canyon fill during the Holocene by the alongslope Labrador Current, with only minor down-canyon sediment supply. In the active canyon depositional phase, turbidity currents were of variable size, reaching thicknesses >390 m at 40 km down canyon. Numbers of sand beds and mean grain size decrease down canyon, which is inferred to result from rapid entrainment of ambient seawater on the steep gradient and a downflow thinning of the lower part of the current with fine sand in suspension. Silt becomes increasingly segregated from muds downcanyon as a result of floc break-up and re-formation. The processes inferred from Halibut Canyon are representative of other canyons on formerly glaciated margins.

The Mariner Field, Block 9/11a, UK North Sea

Abstract The Mariner Field is located on the East Shetland Platform in UK Block 9/11, 320 km to the NE of Aberdeen. The 9/11-1 well was drilled in 1981, discovering oil in the Paleocene Heimdal Sandstone Member and the Paleocene Maureen Formation. The deeper Maureen Formation was deposited on a submarine slope as canyon fill, and overspill canyon sands and debrites. The Heimdal Sandstone Member was deposited above the Maureen Formation on the same inherited, but younger, submarine slope system as deep-water slope channels, and is encased within suspension-deposited Lista Formation claystones. These slope channel sands have undergone post-depositional remobilization and sand-injection processes, leading to the complex sandstone geometries identified and mapped on seismic data. During a 36-year period, 28 exploration, appraisal and production test wells were drilled in UK Block 9/11, but only now is the field finally undergoing development. The long interval between discovery and development is due to several key issues, including the fact that development of heavy oil is technically and commercially challenging, and that the seismic imaging of the Heimdal Sandstone Member has been difficult or not possible until recently. These challenges are being overcome and the Mariner Field started producing in August 2019.

Emergence of a submarine canyon, Crotone Basin, southern Italy

Abstract The Serra Mulara canyon is a middle Pleistocene submarine canyon developed along the Ionian coast of Calabria, southern Italy, now exposed on land due to the long-term regional uplift of the area. New data have allowed recognizing three depositional sequences in the upper part of the succession, probably glacio-eustatic in origin, documenting an evolution of depositional systems that reflect the emergence of the canyon. Sequence 1 shows a rapid shift from turbidites and hemipelagites accumulated in the upper part of the canyon fill to forced regressive deltaic deposits, which reflect a marked shallowing of the area. Sequence 2 consists of estuarine transgressive and deltaic highstand deposits, whereas Sequence 3 is fully composed of fluvial deposits, testifying the emergence of the area. The upper part of the Serra Mulara succession is an useful example showing the transition from submarine canyon to continental settings, a situation that is not adequately documented in the literature, and is also relevant to better reconstruct the timing of the uplift of this part of Calabria.

Slope fan depositional elements evaluation: Implication for reservoir depositional origin in the deep offshore Niger Delta Basin, Nigeria

A study on the slope fan depositional element evaluation with the implication for reservoir depositional origin from the deep offshore Niger Delta Basin, Nigeria has been carried out. This involved an evaluation of the spatial distribution of reservoir depositional facies and their textural properties from deepwater cores obtained at different stratigraphic intervals. Six lithofacies were sedimentologically described based mainly on the lithological composition, textural characteristics, sedimentary structures, sediment concentration, particle cohesion and particle support mechanisms namely coarse-grained clast-supported sandstones, medium-grained normally graded sandstones, parallel laminated sandstones, cross to convolute laminated sandstones, mud-rich heterolithic and massive mudstones. They were genetically grouped into debris flow, turbidity current flow and overbank mud lithofacies associations. Depositional architectures varied from amalgamated channel sands and incised canyon fills to lobate sands. The lobate deposits were dominated by suspension settling and traction depositions due to fluid turbulence and bottom current reworking respectively, and were documented within the mid fan and outer fan complexes. The inner fans and the canyon fill deposits were dominated by debris flows associated with high density, clast-supported laminar flows. The study inferred that the erosion and channelization of the subaerially exposed Niger Delta continental shelf during an early forced regressive event triggered the accumulation of the Q-Sands by debris flow process in an inner fan environment while a short-lived early rise normal regressive event that followed an earlier forced regressive deposits brought about the mobilization of the R-Sands in an entrenched channel levee setting in a mid-fan environment. The continued aggradation of the continental shelf in the fluvial to shallow-marine environments during the early rise normal regression resulted in the delivery of mudstones of low density turbidity flows to the outer fan environment.

Continental slope-confined canyons in the Pearl River Mouth Basin in the South China Sea dominated by erosion, 2004–2018

Repeat multibeam bathymetric surveys conducted in 2004, 2005 and 2018 show that seven slope-confined canyons on the continental slope of the Pearl River Mouth Basin, South China Sea, were dominated by large volume, widespread erosion. Erosion volumes were up to 3.4 times greater than deposition volumes. Erosion-dominated areas of the canyons are up to 2.3 times greater than areas dominated by deposition. Average rates of erosion (ranging from 0.7 to 0.8 m/yr) were greater than average rates of deposition (ranging from 0.5 to 0.8 m/yr). In plan view, the erosion-dominated zones exhibit two characteristic shapes: (1) linear, found mainly in upper canyon reaches, distributed predominantly along canyon axes and at the base of eastern canyon walls, and; (2) blocky, found mainly in lower canyon reaches, widely distributed along the steep canyon walls and on lower-canyon interfluves. The deposition-dominated zones are scattered along canyon floors and walls. Seismic reflection data show lateral shifts of canyon fill deposits through time, indicative of longer-term eastward canyon migration. The linear erosion-dominated zones may be attributed to erosive turbidity currents triggered by energetic internal solitary waves shoaling on the shelf. The eastward canyon shifts were likely induced by rapid near-bed eastward currents generated mainly by westward propagating powerful internal solitary waves of depression. The widespread erosion in the deeper canyon areas and interfluves is likely a consequence of slope instabilities associated with the presence of gas hydrates. This study indicates that active sedimentary processes can occur in slope-confined canyons even during sea level highstands. Local, site-specific oceanographic and geological features (e.g., internal solitary waves, gas hydrates) can significantly increase sedimentary activity in and around submarine canyons.

Interwell EOR Pilot Proves Advantages of Polymer Flooding

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 190175, “Results of the UK Captain Field Interwell EOR Pilot,” by Annette Poulsen, SPE, Adam Jackson, SPE, Nicolas Ruby, SPE, and Karl Charvin, Chevron; Michael Shook, Mike Shook and Associates; Varadarajan Dwarakanath, SPE, and Sophany Thach, Chevron; and Mark Ellis, prepared for the 2018 SPE Hydraulic Fracturing Technology Conference, Tulsa, Oklahoma, USA, 14–18. The paper has not been peer reviewed. This paper discusses an enhanced-oil-recovery (EOR) polymer-flood pilot at the Captain field in the UK North Sea during 2011–2013. The polymer flooding accelerated 6 years of potential waterflood recovery to 1 year and minimized potential water injection and handling by 25.2 million STB. A polymer incremental recovery of 16% original oil in place and improved sweep of 4.7 million STB demonstrated the advantage of using polymer EOR for viscous oils. Finally, the pilot data provided sufficient information to deliver a reliable subsurface assessment for the full-field project. These data also provide evidence that chemical-flood pilots not only can be economical but also can compete economically with waterflooding in some challenging locations when designed and operated efficiently. Introduction The Southern Upper Captain Sandstone (SUCS) reservoir is a complex channel in-fill of a localized canyon eroding the underlying Mid Captain Shale (MCS) and Lower Captain Sandstone (LCS). The canyon was created when two megaslump scars merged into a linear valley cut, giving the reservoir its characteristic shape. The slump scar process also triggered deposition of debrites (a mixture of MCS and LCS sediments) of poor reservoir quality, isolating the underlying LCS from the subsequent SUCS canyon fill. Fluids from the Captain field are unlike those normally encountered in black-oil reservoirs. The fluid is a low-gravity oil with a relatively low dissolved-gas/-oil ratio. The oil is heavily biodegraded with some property gradation across the field. There is an apparent general increase in biodegradation from east to west. The oil in the SUCS is analogous to that in the main part of the Upper Captain Sandstone (UCS). Pressure/volume/temperature and special core-analysis laboratory data reveal a highly unfavorable calculated endpoint mobility ratio equal to 31. The following field observations support the adverse mobility ratio: Strong coning tendency Early water breakthrough Modest oil-rate decline Long oil-tail production in waterflood-recovery profiles Sharp oil-saturation changes between unswept and swept regions Injected water slumping to the base of the reservoir, advancing along the base of the sand, and bypassing the oil Pilot Objectives, Mechanisms, and Implementation The polymer flood for the field was originally envisioned in the field- development plan, and the concept was included in the original facilities design to enable a field trial. The major challenge in deploying a polymer flood is field implementation. Though onshore polymer flooding may be considered a mature technology, field experience is difficult to transfer and the offshore environment adds another level of complexity.

Morphology, architecture, and evolutionary processes of the Zhongjian Canyon between two carbonate platforms, South China Sea

Two isolated Neogene carbonate platforms (Xisha and Guangle carbonate platforms) have developed in the rifted uplifts since the Early Miocene. A large-scale submarine canyon system, the Zhongjian Canyon (ZJC), has developed in the tectonic depression between the two platforms since the Middle Miocene. High-resolution bathymetry data and 2D and 3D seismic data reveal the existence of the ZJC on the present seafloor, as well as in Neogene intervals. It exhibits typical characteristics of deepwater canyons that cut the surrounding rocks and indicate strong erosional features. The ZJC resulted from northwest–southeast strike-slip fault activities during synrift and postrift stages, and it periodically grew during the development of carbonate platforms since the Middle Miocene. We identified four cycles of parallel to subparallel high amplitude and dim reflectors in seismic data, which we interpreted as alternating canyon fill, based on the interpretation of seismic facies. Thus, the sedimentary evolution of the ZJC can be divided into four typical stages, which were in the Middle Miocene, Late Miocene, Early Pliocene, and Pleistocene. Considering the tectonic background of the carbonate platforms, as well as the on-going igneous activities, the sediment filling the canyon could be derived from a mixture of carbonate clasts, igneous clasts, mud, and silt. The laminar high-amplitude reflectors and dim-reflector package represented a fining-upward sedimentary cycle. The coarse-grained sediment in canyon fillings could be turbidites, carbonate debrites, and even igneous clasts. In contrast, the fine-grained sediment is likely to be dominated by pelagic to hemipelagic mud, and silt. This case study describes a deepwater canyon under a carbonate-dominated sedimentary environment and has significant implications for improving our knowledge of periplatform slope depositional processes. Furthermore, the insight gained into periplatform slope depositional processes can be applied globally.

Depositional environment of the early Pleistocene Castlepoint Formation, New Zealand: a canyon fill in situ

ABSTRACTThe early Pleistocene (early Nukumaruan) Castlepoint Formation cropping out on the Wairarapa coast contains a diverse molluscan, bryozoan and barnacle assemblage, with a few brachiopods, corals, echinoids, crabs and polychaetes, comprising mixed warm- and cool-water taxa and outer shelf and shallow-water taxa. Sedimentary structures within the beds (fluid release structures, steep original dips, large load casts, displaced blocks) confirm a dynamic depositional setting by gravity sliding into what is interpreted as a canyon head. The barnacle- and bryozoan-rich molluscan coquina (barnamol and bryomol) that makes up much of the Castlepoint Formation comprises thanatocoenoses resulting from transportation of shallow-water elements, which accumulated deeper-water taxa in transit, to settle in a shelf-edge canyon environment. We interpret all stratigraphic contacts as sedimentary ones; the formation is essentially a canyon fill in situ.

The study of deep water submarine reservoir in Bangle Bay Basin

ABSTRACTAlthough the huge potential of the Bangle Bay Basin has been proven by a series of discoveries, recent drilling and other studies still have not demonstrated the mechanism of hydrocarbon accumulations in Bangle Bay Basin because of the low exploration degree and less geological data available. So, it is difficult to identify and predict the distribution patterns of the main gas reservoir by now. Based on a review of previous work and the latest exploration activities in the study area, the depositional environment and reservoir distribution had been discussed, and thereby assess the location of reservoir–seal couplets for the purposes of stratigraphic traps identification and prospect evaluation within the study area. This paper has also discussed the sequence stratigraphic framework, depositional environment, and facies features by using the biostratigraphic, geochemical analyses and wireline, image logs data. Various broad depositional environments and depositional subsettings have been identified or updated, meanwhile some new environment modeling had been proposed. In this article, reservoir geology study had been conducted after regional depositional feature analysis. Reservoir architecture had been summarized as mouthbars, submarine canyon fill, submarine channels, and levees. Most prospective reservoir intervals identified within the study area are in the Lower Pliocene, Upper Pliocene, and Lower Pleistocene formations.

Source and sink characteristics of the continental slope-parallel Central Canyon in the Qiongdongnan Basin on the northern margin of the South China Sea

The “source-conduit-sink” model is crucial for studying deep-water sedimentary systems along a continental margin. Using seismic data, bulk rare earth element compositions of sediments and zircon U-Pb age data, we examined the supply and deposition (i.e., the source and sink) of the sediments in the Central Canyon of the South China Sea. Five phases of secondary canyon fill are present in the Central Canyon. The natural levees developed at the head of phase 1 of the secondary canyon deposits indicate that the Central Canyon initially developed at 10.5Ma. The sediments in the Central Canyon were supplied by the Ledong submarine fan, and the provenance of the material in the Ledong submarine fan and Central Canyon was eastern Vietnam. Large amounts of sediments were transported through the Central Canyon to the Shuangfeng Basin and deposited during four phases of submarine fan development. Phases 1–3 of the Shuangfeng submarine fans are composed of deep-water branching channel and inter-channel sediments. Phase 4 of the Shuangfeng submarine fan consists of deep-water channel and lobe sediments. Tectonic events, including the broad uplift of the Tibetan Plateau and central-southern Vietnam during the late Miocene, reversal of the strike-slip Red River Fault, and rapid subsidence in the Qiongdongnan Basin at approximately 5.5Ma, provided favourable conditions for the growth of the Ledong submarine fan, Central Canyon and Shuangfeng submarine fan system.

Seismic stratigraphy and tectono-sedimentary framework of the Pliocene to recent Taixinan foreland basin in the northeastern continental margin, South China Sea

The Pliocene to recent Taixinan basin is a unique foreland basin built on the northeastern part of the northern passive margin of the South China Sea (SCS). We have used multichannel seismic profiles tied to well controls from ODP Leg 184 to investigate the tectonic and sedimentary characteristics of the foreland basin. We defined three seismic sequences, dated respectively to the Pliocene (5.33–2.5 Ma), early Quaternary (2.5–1.0 Ma), and late Quaternary (1.0 Ma–present). They represent three stages of evolution of the foreland basin. We have recognized seven types of seismic facies, which are parallel-to-subparallel, progradational, fill-type, divergent mounded, wavy, lenticular, and chaotic facies, and are interpreted as hemipelagic deposits, deltas, submarine canyon fills, levees, sediment waves, submarine fans, and mass transport deposits, respectively. Seismic facies analysis indicates that sedimentation within the foreland basin has been dominated by turbidity currents and the other gravity transport processes. Tectonically, the foreland basin consists of three structural zones: an eastern wedge-top, a central foredeep, and a western forebulge zones. Different from a typical foreland basin, however, the basin extends in the northeast–southwest direction, which is oblique to the north–south-striking Taiwan orogenic zone, but parallel to the northern SCS passive margin, where the basin is hosted, suggesting that the foreland basin is significantly influenced by the development of the passive margin. In addition, the basin displays a distinctive inverted-triangle-shaped downstream-converging sediment dispersal system instead of ideal transverse or longitudinal drainage systems common in a typical foreland basin. We have suggested that the Pliocene to recent Taixinan basin is an atypical foreland basin, which was formed as a flexural response of tectonic loading by the Taiwan orogenic wedge, but strongly affected by its passive continental margin background.