Seismic Geomorphology Research Articles

Mechanism and controlling factors of mass transport complexes migration: A case study of the mass transport complexes in the taranaki deep water basin, New Zealand

Mass transport Complexes (MTCs) form significant sediment accumulations in continental slopes, hold key insights for natural hazard prediction and offshore oil exploration. This paper uses high-definition 3D seismic data to reconstruct the seismic geomorphology and sedimentary dynamics of MTCs, meticulously exploring the depositional systems of the Tanaraki Basin, New Zealand. It deciphers by kinematic notation, seismic faciess, quantifies megaclast morphological characteristics, in conjunction with the basal slope and channel structure development as the migration or kinematics of MTCs. Five seismic facies categories and dynamic traits—compression ridges, thrust faults, slides, grooves and slope terraces are distinguished in MTCs. Based on attributes maps and geomorphological interpretations, MTCs is segmented into four zones, showing combined effects of levée, basal slopes, and megaclast clusters on its migration. Lithological and topographical variations along these features modulate erosion properties and MTCs mobility, with base height shifts guiding local migration trajectories. The results of megaclast parameters in Zones 1 and 3 tune our understanding of stress patterns and directionality shifts, highlighting the complex dynamics at play. Notably, the differential motion triggered by levees instigates longitudinal shear zones. At critical migration disparities, MTCs fracture at these weak points, discharging pore pressure and filling fractures with fines, birthing “promontory” formations marked by low-amplitude fills. This work, therefore, establishes a groundbreaking migratory model that synthesizes the impacts of levees height, rock type variability, and megaclasts accumulation intensity, depicting a fragmented migration pattern. This study not only enriches our grasp of MTCs behavior in deep-water contexts but also furnishes a robust scientific foundation and predictive tool for gauging the hazards that MTCs may pose to underwater structures, thus carrying substantial theoretical and applied significance.

Interpreting environments of deposition from facies analysis of outcrop versus seismic reflection data: A cautionary tale from the Mount Messenger Formation, Taranaki Basin (New Zealand)

The lower part of the Mount Messenger Formation, which crops out along the North Taranaki coast (North Island, New Zealand), is widely regarded to display classic examples of exhumed basin floor fan strata. This interpretation is supported by numerous publications on the sedimentary facies and depositional environments inferred for these strata, which are exposed in coastal cliff exposures about 20 m high with limited lateral extent. Consequently, for almost three decades, this succession has served as an analogue and training ground for geoscientists investigating the features of basin floor fan deposits and their reservoir characteristics. Here, we bring together seismic stratigraphy and seismic geomorphology of 2D and 3D seismic reflection datasets, as well as photogrammetric models based on images collected using uncrewed aerial vehicle (UAV) drones from selected locations along the outcrop belt to challenge this paradigm. We analyzed seismic reflection data in an area immediately offshore and down-dip of the strata exposed in the coastal outcrop and found no objective criteria for submarine fan depositional elements based on accepted seismic stratigraphic criteria. Furthermore, mapping of seismic reflectors revealed large submarine channel systems (up to 3 km wide and up to 200 m deep) within the lower part of the Mount Messenger Formation. Submarine channel depositional elements (less than 250 m wide and 25 m thick) are also observed to incise through the outcrops, but they are generally below seismic resolution. In the context of the regional geology, we conclude that the lower Mount Messenger Formation accumulated as continental slope sediments cross-cut by channels rather than as basin floor fans. This study issues a cautionary tale about applying facies analysis to outcrop with limited 3D exposure to interpret sedimentary environments. The spatial distribution of facies and architectural elements viewed in seismic data are invaluable for testing the veracity of facies interpretations.

Application of 9-component S-wave 3D seismic data to study sedimentary facies and reservoirs in a biogas-bearing area: A case study on the Pleistocene Qigequan Formation in Taidong area, Sanhu Depression, Qaidam Basin, NW China

To solve the problems in restoring sedimentary facies and predicting reservoirs in loose gas-bearing sediment, based on seismic sedimentologic analysis of the first 9-component S-wave 3D seismic dataset of China, a fourth-order isochronous stratigraphic framework was set up and then sedimentary facies and reservoirs in the Pleistocene Qigequan Formation in Taidong area of Qaidam Basin were studied by seismic geomorphology and seismic lithology. The study method and thought are as following. Firstly, techniques of phase rotation, frequency decomposition and fusion, and stratal slicing were applied to the 9-component S-wave seismic data to restore sedimentary facies of major marker beds based on sedimentary models reflected by satellite images. Then, techniques of seismic attribute extraction, principal component analysis, and random fitting were applied to calculate the reservoir thickness and physical parameters of a key sandbody, and the results are satisfactory and confirmed by blind testing wells. Study results reveal that the dominant sedimentary facies in the Qigequan Formation within the study area are delta front and shallow lake. The RGB fused slices indicate that there are two cycles with three sets of underwater distributary channel systems in one period. Among them, sandstones in the distributary channels of middle-low Qigequan Formation are thick and broad with superior physical properties, which are favorable reservoirs. The reservoir permeability is also affected by diagenesis. Distributary channel sandstone reservoirs extend further to the west of Sebei-1 gas field, which provides a basis to expand exploration to the western peripheral area.

About this title - Seismic Geomorphology: Subsurface Analyses, Data Integration and Palaeoenvironment Reconstructions

The spatial extent and quality of seismic and subsurface datasets have substantially improved in recent years due to traditional hydrocarbon activities and the emergence of green technologies like offshore wind. This Special Publication investigates the opportunities for (re)investigating past environments using seismic geomorphology and its integration with other datasets.

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.

Seismic geomorphological analysis of submarine fan architecture in the Baiyun Sag, Pearl River Mouth Basin: Impact of second-order relative sea-level change

Whereas the effects of high-order relative sea level change (3rd-order and higher) on the formation and architecture of submarine fan systems are relatively well established, a lack of large-scale spatial and temporal data has resulted in the impacts of low-order relative sea level change (i.e., 2nd-order) eluding characterization. With the aim of revealing the impacts of 2nd-order relative sea level, this study applied regional-scale seismic geomorphology to examine 142 Miocene-aged (21–8.2 Ma) submarine fans in the Baiyun Sag of the Pearl River Mouth Basin (China), integrating a large 3D seismic volume (6000 km2), well logs and core data. By extracting seismic attributes calibrated to well data, architectural elements were interpreted, statistically correlated, and their evolution through time was assessed. The results were as follows: (1) architectural elements of submarine channels and lobes, as well as associated highstand deltas, shelf-margin deltas and incised valleys, were identified based on their seismic geomorphological features and location, revealing that submarine channels shift paleo-seaward from incised valleys and feed lobes; (2) there is a positive correlation between average width of submarine channels and average area of lobes, as well as between the average width of incised valleys and average width of submarine channels; (3) the size of architectural elements is inversely related to proportion of sand; and most importantly, (4) the size variation of architectural elements coincides with changes in 2nd-order relative sea level. Results also indicate that rapid tectonic subsidence played an important control on the size and sandiness of deep-water architectural elements. The findings of this study may inform reconstruction of submarine fan systems and prediction of their petroleum reservoir potential in other systems globally.

Seismic geomorphology: subsurface analyses, data integration and palaeoenvironment reconstructions – an introduction

Abstract Since the last Special Publication on seismic geomorphology, the application of seismic data has grown substantially, revolutionizing our understanding of basin evolution in the process. The papers presented here provide an insight into the direction of travel for seismic geomorphological analyses and how the science has evolved since 2007. New methods of data collection, new methods of processing and visualization, and the integration of new types of complementary data, all have played a role in maximizing the potential palaeo-environmental insights that can be derived from such studies. The submissions range across different geological settings, consisting of glacial, fluvial, volcanic, deltaic and slope settings. Many of these studies integrate different methods, showing what can be achieved by combining multiple datasets to understand the subsurface. As more legacy datasets become available, the observed acceleration in seismic data availability and the associated publications will likely continue. Newer methods and greater knowledge of the subsurface are yielding a greater understanding of not just the palaeoenvironments, but also what generates seismic reflectivity in the subsurface. The study of seismic geomorphology remains in its infancy, and much exciting research potential is yet to be realized.

Glacial seismic geomorphology and Plio-Pleistocene ice sheet history offshore NW Europe

Abstract Plio-Pleistocene records of ice-rafted detritus suggest NW European ice sheets regularly reached coastlines. However, these records provide limited insight on the frequency, extent and dynamics of ice sheets delivering the detritus. Three-dimensional reflection seismic data of the NW European glaciated margin have previously documented buried landforms that inform us on these uncertainties. This paper reviews and combines these existing records with new seismic geomorphological observations to catalogue landform occurrence along the European glaciated margin and considers how they relate to ice sheet history. The compilation shows Early Pleistocene ice sheets regularly advanced across the continental shelves. Early Pleistocene sea-level reconstructions demonstrate lower magnitude fluctuations compared to the Middle–Late Pleistocene, and more extensive/frequent Early Pleistocene glaciation provides a possible mismatch with sea-level reconstructions. This evidence is discussed with global records of glaciation to consider possible impacts on our wider understanding of Plio-Pleistocene climate changes, in particular how well Early Pleistocene sea-level records capture ice sheet volume changes. Resolving such issues relies on how well landforms are dated, whether they can be correlated with other proxy datasets, and how accurately these proxies reconstruct the magnitudes of past climatic changes. Many questions about Pleistocene glaciation in Europe and elsewhere remain.

Seismic geomorphology of the deepwater sediment dispersals systems in the drift phase of the Mundaú sub-basin, equatorial margin, Brazil

The Ceará Basin, located in the Brazilian Equatorial Margin, represents an exploratory frontier situated in a complex structural framework. The basin observed a dynamic interplay of extensional, transtensional, and transpressional regimes, registered by several sedimentary intervals and unconformities poorly documented by wells, especially at the deeper portions. In this study, based on 3D seismic and well data from the Mundaú Sub-Basin, we interpreted the main seismic sequences of the drift phase to build a Relative Geological Time (RGT) model, based on a semi-automatic seismic traces correlation matched with the well top formations. A seismic attribute analysis from key seismic surfaces extracted from the RGT, highlights the main sediment dispersal routes revealing a significant change after the Mid-Eocene, once sedimentation overpassed a topographic barrier created by fault reactivations, in a transpressional regime, associated with the Romanche Fracture Zone. The integration of seismic and well data affords a deeper understanding of basin dynamics, revealing how sedimentary processes respond to shifts in tectonic stress in this portion of the basin.

Seismic geomorphology of the basin floor area in the Northern North Sea: evolution of the Frigg submarine channels and their influence on sediment distribution

Seismic geomorphology of the basin floor area in the Northern North Sea: evolution of the Frigg submarine channels and their influence on sediment distribution

Hydrostratigraphic decomposition of fluvio-deltaic sediments inferred from seismic geomorphology and geophysical well logs in the Pannonian Basin, Hungary

Heterogeneity and anisotropy of lithological units influences hydraulic conductivity on several scales. The purpose of this study is to develop a novel method supporting hydrostratigraphic classification by considering horizontal and vertical variations of sand content in relation with the paleo-depositional environment. The workflow was applied for the uppermost ca. 1800 m thick fluvio-deltaic deposits (Great Plain Aquifer) of late Neogene to Quaternary age basin-fill succession in the eastern part of the Pannonian basin in Hungary. Five combined 3D seismic volumes, seven master horizons, and 30 well logs were analyzed. First, RMS amplitude maps were extracted to interpret the seismic geomorphological features and depositional architectures. Their associated lithology was inferred from wireline logs (GR and SP) by calculating the shale volume and the net-to-gross sand ratio for 30 m thick intervals. These were used to calibrate the seismic facies as a proxy for the horizontal distribution of sand versus shale. This method allowed the identification of sand bodies, i.e.: deltaic lobes, complex channel belts, simple fluvial channels behaving as aquifers, and the dominantly muddy delta plain to flood plain suits as aquitard. The vertical pattern of sand distribution was also evaluated. Three major stratiform and some corridor-like minor hydrostratigraphic units were defined instead of the former regional (basin) scale aquifer unit. 1) Laterally extended interval of stacked deltaic lobes of high sand ratios and high rate of connectedness, at the bottom of the studied interval. 2) General presence of extended muddy floodplains with anastomosing river systems, characterized by 100–200 m wide channels, low sand ratio, and limited connectedness: 3) widespread meandering and/or braided river systems with high sand ratios and high connectedness in the Quaternary. Within unit 2) spatially and temporally variable appearance of major 500–3600 m wide meandering channel belts produce locally high sand-ratio corridors in the NE-SW direction. A workflow adapted from the oil-and-gas industry was successfully applied to distinguish units of varying sand content and hydraulic conductivity. This approach can be used on basin to local scale to build a spatially complex facies-based model of hydrostratigraphy. Thus, a robust heterogeneous geological model serves as a base for investigating fluid flow on the required scale.

Seismic geomorphology analysis and petroleum geology significance of presalt Jurassic carbonate in the right bank of Amu Darya River

Paleogeomorphological pattern has a great influence on the formation of carbonate reef-shoal complexes and the evolution of carbonate reservoirs. Accurate paleogeomorphology restoration is one of the significant tasks while exploring oil and gas stored in carbonate rocks. However, the previous paleogeomorphology restoration methods mostly rely on high-density drilling data or high-quality seismic data. The applicability of these methods to areas with low-quality seismic data of presalt reservoirs and less drilling control is often low, and they cannot accurately restore paleogeomorphology. This will seriously affect the success rate of oil and gas exploration in presalt reservoirs. Hence, this study aims to address the problem associated with paleogeomorphology restoration under the conditions of highly flexible salt-gypsum rock and low-quality seismic data. By comparing the paleogeomorphology restoration principles of the impression and residual thickness methods and considering multiple factors such as sediment filling and tectonic evolution settings, an innovative model representing the relationship between geomorphology and seismic attributes was established and the paleogeomorphology in the period of deposition of the Middle Jurassic Callovian strata in the eastern part of the right bank of Amu Darya River was restored based on seismic geomorphology, 3D seismic data, drilling data, well log data, core data, and thin-section data. Based on the analysis of the reconstructed paleogeomorphology, it is observed that the high paleogeomorphology shoals in the western part of the study area obstruct the growth of the eastern shoals, affecting the development thickness. However, the quality of thin-layered shoal reservoirs in the eastern part is superior to those in the western part. The distribution of well-developed thick shoals and high-quality reservoirs in this area exhibits obvious spatial differentiation on the plane. Under the unique paleogeomorphology pattern of alternate uplifts and depressions in this area, the quality of reservoirs in the western part is poor, the development quality of reef-shoal reservoirs in the central and eastern region is superior, and the reservoirs in the paleogeomorphologic lowlands are poorly developed.

Geomorphologic control on the evolution of Middle-Late Miocene submarine channels in the Southern Taranaki Basin, New Zealand

The Clifdenian-Tongaporutuan interval in the Southern Taranaki Basin experienced significant activity by turbidity flows during the Middle to Late Miocene, resulting in the formation and burial of several submarine channels. The chronological evolution of these channels is difficult to prove due to their architectures, repeated cut-and-fill, stacking patterns, erosive and erosional natures, and spatial-temporal interactions. In this study, high-quality 3D seismic reflection data from three industrial seismic reflection surveys, combined with five exploration industrial standard wellbore data, were used to analyze the geomorphologic controls on the evolution of fourteen channels within the Clifdenian-Tongaporutuan interval (Middle to Late Miocene) of the southern Taranaki Basin. Our seismic geomorphological analysis, which included seismic facies, slicing, and seismic attribute techniques, revealed that the channels can be classified into two main groups: isolated and amalgamated stacks. These groups may further include high sinuosity-meandering, low sinuosity-meandering, and straight channels. Additionally, gamma-ray logs indicated cylindrical, bell, and serrated trends of sandstone within a thick shale interval, indicating the presence of submarine channels in the study area. Furthermore, the complex spatial interactions of the channels, including architectural variation, and their temporal evolution reflect the activities of different turbidity flow regimes and the interaction with seafloor topography. These interactions, along with a balance between waxing and waning energy phases, influenced the evolution, architecture, and scale of the channels. Importantly, the eustatic sea-level fall in the late Waiauan at approximately 13 Ma, increased clastic sediment supply (climate) and tectonic activities related to rifting and contraction in the Middle Miocene played a significant role in shaping the channels. The workflow, integrated analysis, findings, and the unique case study area presented in this study contribute to research on submarine channels and provide insights into seismic geomorphology, seismic attributes, paleoenvironment reconstruction, the Taranaki Basin, climate, sea-level, and tectonics.

Three-dimensional seismic architecture of an Upper Cretaceous volcanic complex and associated carbonate systems; Taylor Group, Elaine field, South Texas, USA

The seismic architecture of a tuff-dominated volcanic complex and the associated carbonate systems in the Upper Cretaceous Taylor Group (Anacacho Limestone) Elaine field in South Texas was examined using a three-dimensional seismic dataset. The investigation demonstrates that the combination of traditional seismic lithofacies analysis and seismic sedimentology allows the visualization and interpretation of volcanic elements and penecontemporaneous carbonate lithofacies at the scale of tens of meters. A wireline-log based, rock-physics model was analyzed and calibrated using core samples, which link volcanic and carbonate lithofacies to 90°-phase seismic amplitude events. Seismic-velocity effects permit the identification of subtle volcanic lithofacies changes such as low-velocity tuff bodies or high-velocity basalt intrusions. Also, frequency fusion expands seismic visualization of thick lithofacies bodies (e.g., basaltic dykes) to the 100-m range and seismic facies analysis helps understand interrelationships between the components in and adjacent to the volcanic body. Horizontal seismic slices reveal seismic geomorphology at multiple stages of volcanic activity. This investigation reveals three major seismic facies systems (1) a magma-feeder (i.e., plumbing) intrusive system beneath the volcano, including deep faults, dykes and sills, and remnant radial/concentric fault systems; (2) a large (4000–5000 m diameter) volcanic complex consisting of a deep crater (300-m negative feature below the paleo-sea floor), a large mound (200-m positive feature above the paleo-sea floor), multiple secondary craters filled predominantly with tuffs and less common lava flows; and (3) penecontemporaneous carbonate systems including fringing and mound-top shoals and reefs, lagoon and debris fan aprons at the base of the volcanic mounds. The fringing and mound top carbonate systems were probably in water depths less than 20 m whereas for the fan-apron carbonates, water depths are estimated to be about 140–200 m. These carbonate bodies can form hydrocarbon reservoirs.

Concealed Canyons Delineation and Depositional Elements Analysis Applying a Multidisciplinary Geological and Geophysical Approach: A Case Study of the Pliocene Turbidites, West El-Burullus Area, Offshore Nile Delta, Egypt

A detailed geological-depositional model and a clear understanding of the depositional elements of reservoirs decrease the drilling risks in the development of oil and gas fields. Building an effective geological model is a challenge in West El-Burullus (WEB) area because of its complicated reservoir, which consists of turbidite incised canyons system of Pliocene shales intercalated with sands. These canyons have occurred due to turbidity currents associated with the basin slope forming Kafr El-Sheikh Formation. Deducting the geological-depositional model and basins architecture is carried out utilizing the integration of seismic geomorphology, seismic facies analysis, sequence stratigraphy, and petrophysical analysis. The available datasets comprise a 3D seismic cube and logs of the WEB-1 well. Analyses of these data revealed various lithological facies relations and their paleo-depositional environments. This study demonstrated that Kafr El-Sheik Formation comprises a third-order sequence of turbidite units in-filling a canyon named WEB canyon with five sedimentary facies components: basal lobe through the incised old canyon, amalgamated channels fill, followed by splays, lobes, levees either proximal or distal facies, then the last plugged channels. Time–frequency spectral decomposition of time slices at the base and the top of the WEB canyon assisted the description of the litho-morphological and facies distribution of the concealed Kafr El-Sheikh Formation turbidity incisions and recognized reservoir trending and the canyon fairway. The turbidity facies with high reservoir quality was found in the overbank sedimentary distribution channels such as proximal levees and splays that reflected good to excellent petrophysical reservoir characteristics.

Fluvial reservoir characterization through channel belt dimension and petrophysical analysis

The dimensions and connectivity of fluvial reservoirs vary greatly, making it challenging to characterize them using conventional approaches. In this study integrated channel belt dimension analysis from seismic geomorphology and empirical equations, well log facies, and petrophysical analysis were performed to characterize the fluvial reservoirs. The study interval consists of fluvial deposits and is divided into three reservoir zones, which are defined by four key regional markers (B, D, K, O). In these intervals, six (6) fluvial facies have been identified. Based on the log facies proportions and their stacking relationships, it is interpreted that the reservoirs in Zone 1 (B to D) were deposited in a proximal reach of a meandering system, Zone 2 (D to K) in a marginal marine setting, and Zone 3 (K) in a distal reach of a meandering system. The dimensions of fluvial channels and channel belts were determined using empirical equations. The results were compared with the observed dimensions of fluvial channels and channel belts from the seismic horizon and stratal slices of the same intervals. Zone 1 and 3 are characterized by broad meander belts (1000–4000 m) compared to zone 2 (600–1300m). Petrophysical analysis showed zone 1 and 3 have the better petrophysical properties compared to zone 2. Though zone 3 has the most well-developed sand bodies the best reservoir interval is zone 1 because of its higher porosity. Although channel belt dimensions have a significant influence on reservoir connectivity, they do not seem to have control on reservoir properties. The channel belt dimensions obtained from the empirical equations and interpreted from the seismic geomorphology analysis were found to be strikingly similar. Since three-dimensional seismic data is not available everywhere and seismic imaging quality decreases with depth, empirical equations can be used to analyze fluvial reservoir parameters and their connectivity at greater depths.

Quantitative seismic geomorphology of sediment conduits on an evolving Miocene slope in Taranaki Basin (New Zealand): The influence of increasing slope gradient through time

Submarine canyons, channels and gullies are conduits that transport sediments across shelf-slope margins to deep water. In South Taranaki Basin, an increase in sediment supply through the Miocene resulted in progradation and significant steepening of the slope system. Previous studies have identified numerous sediment conduits developed within this system, however their morphology and morphometric relationships with the depositional slope have not been considered. Here we apply seismic geomorphology to establish the statistical relationships between the metrics of sediment conduits at three stratigraphic intervals between which the slope gradient progressively increased. In the early-Middle Miocene, sinuous upper Moki Formation channel complexes with an average width of 1.1 km developed on a slope with an average gradient of 0.2o, routing sediment from south to north. By the late-Middle Miocene, the slope began to prograde rapidly, concurrent with a regional reorientation of the slope to the northwest, on which the lower Mount Messenger Formation canyon networks developed with a slope gradient of 0.4–1.0o. At shallow slopes of less than 0.5o, canyon morphometrics (mean width 6.6 km) are 1.8–4.7 times larger than on related upper slopes with gradients steeper than 0.5o (mean canyon width of 2.7 km). This significant shift in morphometrics occurs abruptly across the clinoform toe line. Rapid Late Miocene slope progradation resulted in the development of steep clinoform slope surfaces up to 9o, into which linear upper Mount Messenger Formation gully complexes incised. The mean gully width throughout the Middle to Late Miocene interval decreased from 1.3 km to 1.0 km as the slope gradient became steeper. This study documents how the morphology and morphometrics of sediment conduits on the South Taranaki Basin slope system changed through time in relation to changes in depositional slope gradients.

Stratigraphic expression of the Paleocene-Eocene Thermal Maximum climate event during long-lived transient uplift—An example from a shallow to deep-marine clastic system in the Norwegian Sea

Seismic geomorphology and stratigraphic analysis can reveal how source-to-sink systems dynamically respond to climatic and tectonic forcing. This study uses seismic reflection data from the Norwegian Sea to investigate the stratigraphic response to a short-lived (0.2 Myr) period of climate change during the Paleocene-Eocene Thermal Maximum (PETM), superimposed on a long-lived (∼8 Myr) period of hinterland uplift. The data show that long-term uplift resulted in ∼300 m of relative sea-level fall, forced regression and formation of incised valleys during the latest Paleocene-earliest Eocene. The short-lived PETM climate perturbation at ∼56 Ma changed the transport dynamics of the system, allowing sediment to be bypassed to wide channel complexes on the basin floor, feeding a large mud-rich basin-floor fan more than 50 km into the basin. Our analysis also suggest that sediment supply was up to four times higher during the PETM compared to earlier and later periods. Maximum regression at ∼55.5 Ma resulted in the formation of a subaerial unconformity. The style of subaerial incision was dictated by shelf accommodation and proximity to the area of direct sediment input. Out-of-grade shelves and slopes sourced by littoral drift were prone to incision, but direct-fed and graded shelves and slopes were not. Despite maximum regression, sediments were not transported significantly beyond the toe-of-slope aprons, suggesting that rapid climate change was more efficient in bypassing sediment to the deep-water than low stands of sea level. As long-term accommodation increased after the PETM, deltas were still able to reach shelf edge, but periods of maximum regression were not associated with deep incisions along the outer shelf and only smaller canyons and gullies formed. The shelf-slope wedge was finally transgressed at ∼51 Ma. The age of deep valley incisions overlaps with the time of subaerial erosion in the East Shetland and Faroe-Shetland basins, suggesting a common mechanism for North Atlantic uplift around 55–56 Ma. Other seismic stratigraphic surfaces do not seem to be regionally time-equivalent, highlighting the importance of local controls on internal architecture of shelf-slope wedges. This study demonstrates the high-resolution stratigraphic response to long- and short-term external forcing together with intrinsic processes and can help identify similar relationships in other areas.

Seismic geomorphological analysis of channel types: a case study from the Miocene Malay Basin

Abstract Imaging the subsurface is a major challenge due to many aspects; the most notable is the resolution of the data, which often leads to misinterpretation of reservoir behaviour and depositional environment. Even with the robust tools available to precisely model the subsurface reservoir and depositional architecture, a precise result is still incorrect if derived from an inaccurate subsurface description. Recent advances in 3D seismic geomorphology analytical methods, particularly the application of root mean square (RMS) and frequency decomposition analysis, have enabled detailed imaging, description and classification of subsurface channel networks. Typically, it is easier to image shallow subsurface channels (<500 m depth), but it gets increasingly challenging to recognize channel features at subsurface depths ≥1.5 km. This paper presents the characterization of channel features imaged from such depths within the Miocene section of the Malay Basin, offshore Peninsular Malaysia. An integrated dataset from a selected area in the central region of the Malay Basin was used for this study, including a high-quality 3D seismic cube (1563 km2) and data from one well penetrating the Miocene section of the Malay Basin. We have identified five seismic geobody groups and 10 channel types from both planform and cross-section views. The dimensions, shapes, sinuosities and thicknesses of these channel types vary. Additionally, they display various seismic characteristics in cross-section and planform views. Variability in channel geometries is related to the complex interplay between fluvial and marine processes.

Seismic geomorphology of the Chandeleur submarine landslide in the northern Gulf of Mexico

Abstract The Chandeleur Submarine Landslide Complex occurs on the upper Mississippi Fan of the Gulf of Mexico in approximately 1100 m of water, 200 km SE of New Orleans, Louisiana. This part of the Mississippi Fan received high sedimentation throughout the Pleistocene, causing high pore fluid pressure and abundant slope failures, though few as large as the Chandeleur. Given its large size, proximity to major coastal cities and seafloor infrastructures, we examine the Chandeleur Slide to understand what led to the initial slope failure and decipher its post-failure transport behaviour using 2D and 3D multichannel seismic surveys, high-resolution bathymetric data, and well logs. We find a large sediment mass with a translational-rotational behaviour that was displaced to the south/SE up to 40 km from the source area. The Chandeleur Slide includes extensional faulting in the headscarp area and compressional structures in the toe where confined by a natural ramp-like structure. Beneath the Chandeleur Slide, we identify a regional sand-rich unit (called the Blue Unit) that is known to be overpressured. Beneath the Blue Unit we observe an upward-migrating salt diapir. We suggest one possible scenario for the origin of the Chandeleur Slide is the combined effects of an upward-migrating salt diapir impinging on an already overpressured Blue Unit, leading to the initial failure. The initial failure was followed by retrogressive headwall retreat northward, which created the prominent scarp on the seafloor. In total, the Chandeleur Slide complex covers an area of about 1000 km 2 and contains about 300 km 3 of sediment.