Basin Research

Bouchakour, Massine; Zhao, Xiaoming; Miclăuș, Crina; Yang, Baoquan

doi: 10.1111/bre.12750pmid: N/A

Understanding the interactions of submarine channels with seafloor deformations is challenging as these channels more often involve a wide variety of responses relying on both autogenic and allogenic factors. The effect of active growing structures on channel pathways is well documented, but the evolution of lateral migration and the internal architectures along the deflected channel bends around ongoing active structures remain poorly constrained. Here, we use 3D seismic interpretation and quantitative geomorphologic methods to examine the channel bend morphology and the kinematics of lateral migration near gravity‐driven tectonic deformation. Using high‐resolution seismic reflection data acquired from the offshore Niger Delta, two‐channel levee systems (Amaku Major System and Amaku Channel Levee System) have been recognized in the seismic survey. Each system consists of three channel complexes, recording five types of deflected channel bends, defined here as: (i) avulsed bend, (ii) confined bend, (iii) chute cut‐off bend, (iv) blocked bend and (v) kinked bend. Geomorphologic parameters including bend sinuosity, bend amplitude, along‐bend length, straight‐bend length, channel depth and width, were considered within the deflected channels. Lateral migration estimators; channel lateral shift (SH), and channel lateral spacing (CS), were assessed throughout the distances of cross‐sectional channel patterns. The lateral migration estimators (SH and CS) were used to estimate the expression of internal architectures and the evolution of lateral migration around seabed deformation at the scale of the channel complex. The results show that the morphology and internal architecture of the deflected bends, although developing in the same structural context, display varied responses to structural deformation. Unlike previously published models of channel‐fold interactions asserting tectonics as the solitary driver, here we demonstrate that the channel deflections around structures are sensitive to the lateral confinement produced by sediment relief of the outer levees, and the autogenic forcing of channel mechanisms. This study provides new insights into the evolution of submarine channels in active tectonic settings, shows detailed mechanisms of channel bends at a small scale and offers a better understanding of the distribution of sediments in the deep sea.

Hsieh, Amy I.; Dashtgard, Shahin E.; Wang, Pei‐Ling; Horng, Chorng‐Shern; Su, Chih‐Chieh; Lin, Andrew T.; Vaucher, Romain; Löwemark, Ludvig

doi: 10.1111/bre.12741pmid: N/A

The Taiwan Western Foreland Basin is thought traditionally to have received sediment mainly from Eurasia until the late Pliocene–early Pleistocene, after which time, the Taiwan orogen became the dominant source. However, a combination of clay mineralogy, δ13Corg and C/N of organic matter, and mass‐specific magnetic susceptibility of late Miocene to early Pliocene strata of the Kueichulin Formation indicate that onset of major sediment contributions from Taiwan occurred much earlier, and correlates closely to the uplift and initial emergence of the Taiwan orogen. Clay mineralogy shows an upsection increase in illite and illite crystallinity, and a decrease in chlorite and kaolinite after the late Miocene, and this is attributed to rapid erosion of the Taiwan orogen. Results from δ13Corg and C/N analyses show that organic material in the Kueichulin Formation changed from dominantly marine to dominantly terrestrial in the early Pliocene, and this is linked to the delivery of large quantities of terrestrial organic material from the Taiwan orogen to the adjacent Taiwan Strait. Magnetic susceptibility also decreases significantly during the early Pliocene, resulting from dilution of magnetic minerals through the influx of non‐magnetic minerals delivered from the Taiwan orogenic belt. The establishment of the growing Taiwan orogen as a major sediment source to the Western Foreland Basin occurred at the Miocene–Pliocene transition, about two million years earlier than previously recognized.

Amadori, Chiara; Maino, Matteo; Marini, Mattia; Casini, Leonardo; Carrapa, Barbara; Jepson, Gilby; Hayes, Robert George; Nicola, Chiara; Reguzzi, Simone; Di Giulio, Andrea

doi: 10.1111/bre.12752pmid: N/A

The Tertiary‐Piedmont Basin (NW Italy) is an episutural basin that developed from the late Eocene on the Alps–Apennines tectonic junction. Several coeval geodynamic processes, including the loading and exhumation of the Western Alps, the outward migration of the Apennine accretionary wedge and the opening of the Liguro‐Provençal rift basin, controlled the basin evolution. We integrate fluid‐inclusion microthermometry, low‐temperature thermochronology and burial history with numerical modelling to constrain the palaeo‐geothermal gradients required and evaluate the mechanisms that governed the basin thermal history. Apatite fission‐track and (U‐Th‐Sm)/He analyses of the basal late Eocene turbidites show reset ages of ca. 25 and 20 Ma, respectively, which require temperatures to be >120°C. Homogenization temperatures up to ca. 130°C from fluid inclusion analyses from authigenic minerals confirm the thermochronometric data, supporting a significant post‐depositional heating in the lower sequence of the basin. Stratigraphic reconstructions and decompaction of the basin fill indicate that the maximum burial experienced by the basal strata at 25 Ma is 2.3 ± 0.1 km, which is not sufficient to reset the AFT thermochronometric system when applying a typical geothermal gradient (ca. 20–30°C/km). An elevated geothermal gradient of 45 ± 5°C/km is thus necessary to explain the thermochronometric dates and the elevated thermal signature at shallow depths. 2D numerical simulations indicate that such an elevated palaeo‐geothermal gradient can be best explained by mantle upwelling, consistent with crustal thinning caused by the inception of the Liguro‐Provençal rift basin and related outward migration of the Alpine and Apennine fronts during the Oligocene.

O'Neill, Sean R.; Jones, Stuart J.; Kamp, Peter J. J.

doi: 10.1111/bre.12749pmid: N/A

Significant variations in pore pressure across the Taranaki Basin, New Zealand, are attributed to changes in lithofacies and structure, usefully illustrated in terms of ten areas that we term geopressure provinces, each displaying individual pore pressure trends. Cretaceous to Early Miocene formations in different parts of the basin can be either normally pressured (near or at hydrostatic) or significantly overpressured (up to 28 MPa) at the same depth. Variations in Eocene–Oligocene facies types and thicknesses both within and between geopressure provinces provide first‐order control on the magnitude, distribution and maintenance of overpressure across the basin. Examples of hydraulic compartmentalisation due to sealing faults and stratigraphic architecture are identified within the basin. Deep pore pressure transitions are sealed by diagenetic, structural or stratigraphic mechanisms in different places and are associated with an increase in mudrock volume (reduced permeability) or gas generation. Thus, pore pressure distribution in the Taranaki Basin is controlled by a combination of sediment loading, lithofacies variations, fault zone permeability and structural architecture. This work represents an appraisal of the pore pressure distribution across the whole of a multiphase structurally complex basin, and the approach taken provides a framework for better understanding the distribution of pore fluid pressures and pore fluid migration in other sedimentary basins.

doi: 10.1111/bre.12677pmid: N/A

Yang, Jing; Nie, Junsheng; Zhang, Haobo; Rasmeni, Sonwabile Kidwell; Ncube, Lindani; Niekerk, Helena Johanna; Zhao, Baojin; Hu, Xiaofei

doi: 10.1111/bre.12746pmid: N/A

Understanding the source‐to‐sink relationship of a large river‐marginal sea system is key to using marginal sea sediments to infer terrestrial erosion/weathering variations. The Zambezi River, the largest river in the southern African region, has been transporting large amounts of sediments to the southwestern Indian Ocean since the Cretaceous, which have been often used to infer river integration history and uplift of the southern African region. Thus, characterizing the geochemical features of different parts of the river is the key to correctly interpreting terrestrial sediment signals in the southwestern Indian Ocean drill cores. Here we present the first provenance study based on Sr‐Nd‐Hf isotopic results of river sands from mainstream and tributaries of the Zambezi River. We find that the isotopic signatures of the river sediments are largely consistent with its underlying basements of the different reaches, which suggests the local geology control of the river sedimentary provenance. This result is in line with the studies of the provenance of the Yellow and Yangtze Rivers, which suggest that sediments transported by the upper reaches of large rivers draining interior continents are primarily stored in sedimentary basins on land instead of marginal seas. This study suggests caution must be taken in using sediments of marginal seas to infer erosion history of the hinterland mountain uplift and exhumation.

Lymer, Gaël; Childs, Conrad; Walsh, John

doi: 10.1111/bre.12745pmid: N/A

Low‐angle detachments are fundamental crustal structures found in many extensional systems and plate tectonic boundaries, including onshore extensional basins, rifted margins and mid‐oceanic ridges. Direct observations of the complete geometry of extensional detachments are rare so that aspects of our understanding of their development and evolution rely mainly on proxy observations and numerical simulations. A high‐resolution 3D seismic reflection survey Offshore West of Ireland images a complete corrugated extensional detachment, from its steep oceanward breakaway faults to its back‐rotated domal crest. The detachment surface, the P reflector, developed during the Jurassic hyperextension of the Porcupine Basin and is preserved in its slip position. It covers 95 × 35 km area and has a N‐S elongate domal shape, at right angles to the prevailing extension direction, with a crest at ca. 6.3 s two‐way travel time. It is overlain by a syn‐rift sequence offset by steep frontal faults that pass eastward into shallower, predominantly west‐dipping highly listric faults that merge downwards with the detachment. The detachment has pronounced E‐W corrugations parallel to the basin opening direction, and N‐S lineaments that correspond with the footwall cutoff lines of overlying Jurassic faults. The most significant N‐S lineaments correspond with changes in dip of the detachment. We propose that the geometry of P can be explained by a conceptual model in which the detachment was assembled from initially steep faults that developed at the front of P and back‐rotated to form listric faults during extension, with punctuated oceanward propagation of the segments of the detachment. Comparisons with 2D profiles and 3D surfaces of published detachments suggest that our conceptual model may be applicable to other detachments that accommodate extreme extension at other rifted margins and at mid‐oceanic slow and ultra‐slow spreading ridges.

Gallardo Jara, Rocío E.; Ghiglione, Matías C.; Galliani, Lisandro Rojas; Mpodozis, Constantino

doi: 10.1111/bre.12739pmid: N/A

This contribution characterizes primary lithologic and depositional components of the Magallanes‐Austral basin and defines infill geometries and stacking patterns from seismic and well data. An integrated seismic model is proposed for recognition of rifting, thermal sag and foreland tectono‐stratigraphic phases based on depositional geometries and its relation with the evolving deformational and geodynamic framework. Above a Middle–Late Jurassic extensional phase, evidenced by synrift depositional geometries, follow marine successions representing the subsidence thermal sag phase (Tithonian–Early Cretaceous) characterized by concordant and laterally extensive seismic reflectors. The following foreland phase is described through the evolution and lateral migration history of the foredeep depocentre and concomitant forebulge development. The foreland phase is represented by different stages characterized by asymmetric sedimentary wedges bounded by basal surfaces and/or major unconformities recording transitions from underfilled to overfilled conditions. The accumulated thickness due to lithospheric flexure reflects different foreland subsidence profile patterns across the southern depocentre of the Magallanes‐Austral basin, producing asymmetrical westward and southward thickening wedges. The first Foreland I stage (Coniacian?–Maastrichtian) is recorded as an asymmetric wedge infill, that thins cratonward, with a NW‐trending foredeep axis. The erosive basal foreland surface (BF) at its base deepens towards the west and south along the active margin of the basin, where subsidence was maximum. On top of it, along the western portion of the basin and with a source area from the north, deep‐marine slope deposits and turbiditic complexes were deposited; while on the forebulge to the east, a clastic platform developed. The Foreland II stage (early‐to‐middle Palaeocene–middle Eocene) is characterized by renewed uplift and flexure, and increasing tectonic subsidence rates, building a new clastic wedge‐shaped foreland succession next to the orogenic belt, and a well‐represented forebulge to the east. Subsequently, an extensive diachronous G7 unconformity was generated, eroding locally the previous foreland deposits towards the eastern margin. A pronounced and continuous NW‐SE trending deflection is established subtly to the east. The following Foreland III stage (middle to late‐Eocene–Oligocene) is characterized by a reduction in thrust load along the western active margin, and progradational systems towards the NE, a time during which the subsidence rate decreased and accommodation space was reduced. Deposition occurred within a wide and continuous NW‐SE trending foredeep without a marked forebulge. The top of this stage is the A1 unconformity, marking the beginning of the Foreland IV stage (early Miocene–Neogene), regarded as an overfilled basinal stage without a marked foredeep and major variations in thickness across the extent of the basin. The depositional pattern in this stage is largely conformal and tabular. The proposal model represents an evolutionary example for the internal geometry of deep‐marine foreland basin system, including variables such as tectonic load and flexural subsidence, accommodation space, sediment supply variation, and relative sea‐level fluctuations.

Kudriavtseva, Anna; Sobel, Edward R.; Codilean, Alexandru T.; Meijers, Maud J. M.; Mulch, Andreas; Hoke, Gregory D.; Fink, David; Mikolaichuk, Alexander V.; Fülöp, Réka‐H.; Wilcken, Klaus M.; Enge, T. Gabriel

doi: 10.1111/bre.12751pmid: N/A

Uplift of the Tian Shan range modified regional climate during Cenozoic aridification in Central Asia. This study presents facies analyses and Neogene oxygen and carbon isotopic records from magnetostratigraphically dated terrestrial sedimentary sections on the southern side of the intermontane Issyk‐Kul basin in the Kyrgyz Tian Shan and 26Al/10Be isochron burial ages from the southern and eastern sides of the basin. The δ18O and δ13C data show a positive ca. 2‰ shift in values between ca. 8 and 7 Ma and a change from a negative to a positive trend. This change is attributed to the upwind growth of the Kyrgyz, Kungey and Trans Ili (Zaili) ranges, which diverted the westerlies, thereby changing the Issyk‐Kul basin from a windward to a leeward position, enhancing aridification and establishing the modern‐day spring and summer precipitation regime within the basin. Two 4 to 5 Ma 26Al/10Be isochron burial ages constrain the onset of Sharpyl Dak deposition on the eastern side of the basin; southward paleocurrent directions there suggest the eastward growth of the Kungey range in the Pliocene. Increased subsidence on the southern side of the basin and local tectonically induced river system reorganization led to the commencement of lake formation at ca. 5 Ma, followed by a ca. 2 Ma local depositional hiatus. The transition from sandstones of the Chu sedimentary group to conglomerates of the Sharpyl Dak group, marking a change from fluvial‐alluvial deposits to a proximal alluvial fan, is dated at 2.6–2.8 Ma by 26Al/10Be isochron burial dating on the southern side of the basin, driven either by tectonics or Northern Hemisphere glaciation. This study concludes that the late Miocene–Pliocene northward growth of Tian Shan significantly altered environmental conditions within the range, preventing the moisture‐bearing westerlies from reaching the intermontane Issyk‐Kul basin and promoting lake formation and expansion.

Acevedo, Eliana; Fernández Paz, Lucía; Encinas, Alfonso; Horton, Brian K.; Hernando, Agustín; Valencia, Victor; Folguera, Andrés

doi: 10.1111/bre.12744pmid: N/A

The Middle Jurassic–Early Cretaceous evolution of the Neuquén Basin is traditionally attributed to a long phase of thermal subsidence. However, recent works have challenged this model. In view of this, we study the Late Jurassic Tordillo Formation, a non‐marine depositional unit that marks a shift to regional regression across the basin. Previous studies propose different causes for this regression, including the growth of the magmatic arc in the west, uplift in the south or extension in the north. We studied the Tordillo Formation in sections located at an intermediate position in the Neuquén Basin, in order to understand the tectonic processes active during sedimentation. We present evidence of normal faulting within the Tordillo Formation and the base of the overlying Vaca Muerta Formation. Some of these faults can be attributed as syndepositional. We characterize the Tordillo Formation as part of a distal fan‐playa lake depositional system with a contemporaneous western magmatic arc as the main source of sediment. When compared to the Late Triassic–Early Jurassic NE to NNE‐oriented rifting, which marks the opening of the Neuquén Basin, the Late Jurassic extension shows a switch in stress orientation; the latter is orthogonal to the north‐trending subduction zone. We interpret this change as a renewed phase of back‐arc extension induced by slab rollback along with minor distributed intraplate extension prior to opening of the South Atlantic Ocean.