Seismic stratigraphy and the sedimentation history in the Laxmi Basin of the eastern Arabian Sea:Constraints from IODP Expedition 355

Detailed interpretation of seismic stratigraphic sequences in the Laxmi Basin of the eastern Arabian Sea are presented in this study using closely spaced high resolution multi-channel seismic(MCS)data.Our stratigraphic interpretation is further corroborated using recent drilling results in the Laxmi Basin,derived from the long sediment cores collected during International Ocean Discovery Program(IODP)Expedition 355.Integrated core-log interpretation discussed in the present study,offer important insights about the lithostratigraphic variations in this region.Analyses of multi-channel seismic reflection data reveal five depositional sequences(ranging from Paleocene to Recent)that led to the development of this marginal basin since the Cenozoic period.Regional igneous basement is successfully imaged,which was also validated by deep sea coring during the IODP Expedition 355.In the present study,we primarily focus on the post-rift sedimentation in the Laxmi Basin and its possible mechanisms.Our detailed interpretation in the prevailing tectonic framework of the basin suggests that near-shelf oldest volcaniclastic sedimentation immediately overlying the acoustic basement is linked to the onset of India-Madagascar and India-Seychelles rifting activities during the Late Cretaceous period.Eventually,during the Early-Mid to Late Miocene,the basin received maximum sedimentation dominantly through an extensive mass transport mechanism implying possible large-scale deformation on the Indian shelf.Subsequent sediment input to the basin appears to have been fed variably via the Indus Fan as well as coastal discharge from the Indian mainland.The total sediment thickness in the Laxmi Basin ranges from 1.1 to 3.5 km.New stratigraphic information and sediment isopach maps presented here provide vital information about syn-and post-rift sedimentation pattern in the region and their long term tectonic implications.

Machine learning-supported seismic stratigraphy of the Paleozoic Nubia Formation(SW Gulf of Suez-rift):Implications for paleoenvironmentpetroleum geology of a lacustrine-fan delta

Steeply dipping prograding fan deltas possess high reservoir quality facies that could be excellent targets while exploring for hydrocarbons.Due to their complex stacking nature,and limited examples,delineating their architectural elements is still challenging.In this paper we mainly performed sedimentary facies analysis;applying various disciplines e.g.sequence stratigraphy,seismic stratigraphy,GR-log motifs,and seismic waveform segmentation;so as to adequately depict the reservoir heterogeneity and quality of the Paleozoic Nubia clastics in West Esh El Mallaha Concession(southwest Gulf of Suez rift).Organic maturity prediction,to confirm the hydrocarbon charging from source units to reservoir intervals,was also of most importance in this study.Accordingly,1D basin model was established to define the past geologic events;subsidence,and thermal maturity;and their controls on sedimentary basin evolution and associated petroleum potential.We utilized several key-information scales;e.g.wireline logs,and seismic profiles.Linking different disciplines applied in this study points to a successful integrated reservoir characterization workflow capable of unfolding ancient environments and the associated hydrocarbon potential.The results show that Nubia Formation was built during the lowstandtransgressive phase of a 3rd order depositional sequence.It encompasses fluvio-lacustrine system with eight sedimentary facies associations;form source to sink.Fluvial channels and mouth bars,settled in subaerial and subaqueous settings respectively,represent the most significant reservoir facies in the area.Given best hydrocarbon-reservoir quality,the deltaic mouth bars ought to attract attention of further oilfield development plans and be considered while investigating similar settings.

Neogene faulting and volcanism in the Victoria Land Basin of the Ross Sea, Antarctica

The Neogene Terror Rift in the Antarctic Victoria Land Basin(VLB)of the Ross Sea,Antarctica,is composed of the Discovery Graben and the Lee Arch.Many Neogene volcanoes are aligned in the north-south direction in the southern VLB,belonging to the McMurdo Volcanic Group.However,due to multiple glaciations and limited seismic data,the volcanic processes are still unclear in the northern VLB,especially in the Terror Rift.Multichannel seismic profiles were collected at the VLB from the 32nd Chinese National Antarctic Research Expedition(CHINARE).We utilized four seismic profiles from the CHINARE and additional historical profiles,along with gravity and magnetic anomalies,to analyze faults and stratigraphic characteristics in the northern Terror Rift and volcanism in the VLB.Negative flower structures found in the northern Terror Rift suggest that the Terror Rift was affected by dextral strike-slip faults extending from the northern Victoria Land(NVL).After the initial orthogonal tension,the rift transited into an oblique extension,forming a set of downward concaving normal faults and accommodation zones in the Terror Rift.On the Lee Arch,several imbricated normal faults formed and converged into a detachment fault.Under gravitational forces,the strata bent upward and formed a rollover anticline.Many deep faults and thin strata subjected to erosion facilitated volcanic activity.A brittle volcanic region in the VLB was affected by dextral strike-slip movements and east-west extension,resulting in two Neogene volcanic chains that connect three igneous provinces in the VLB:the Hallett,Melbourne,and Erebus Provinces.These two chains contain mud volcanoes with magnetic nuclei,volcanic intrusions,and late-stage volcanic eruptions.Volcanisms have brought about opposite polarities of magnetic anomalies in Antarctica,indicating the occurrence of multiple volcanic activities.

Evolution of sedimentary environments of the middle Jiangsu coast, South Yellow Sea since late MIS 3

An evolutionary model of sedimentary environments since late Marine Isotope Stage 3 （late MIS 3, i.e., ca. 39 cal ka BP） along the middle Jiangsu coast is presented based upon a reinterpretation of core 07SR01, new correlations between adjacent published cores, and shallow seismic profiles recovered in the Xiyang tidal channel and adjacent northern sea areas. Geomorphology, sedimentology, radiocarbon dating and seismic and sequence stratigraphy are combined to confirm that environmental changes since late MIS 3 in the study area were controlled primarily by sea-level fluctuations, sediment discharge of paleo-rivers into the South Yellow Sea （SYS）, and minor tectonic subsidence, all of which impacted the progression of regional geomorphic and sedimentary environments （Le., coastal barrier island freshwater lacustrine swamp, river floodplain, coastal marsh, tidal sand ridge, and tidal channel）. This resulted in the formation of a fifth-order sequence stratigraphy, comprised of the parasequence of the late stage of the last interstadial （Para-Sq2）, including the highstand and forced regressive wedge system tracts （HST and FRWST）, and the parasequence of the postglacial period （Para-Sql）, including the transgressive and highstand system tracts （TST and HST）. The tidal sand ridges likely began to develop during the postglacial transgression as sea-level rise covered the middle Jiangsu coast at ca. 9.0 cal ka BP. These initially submerged tidal sand ridges were constantly migrating until the southward migration of the Yellow River mouth to the northern Jiangsu coast during AD 1128 to 1855. The paleo-Xiyang tidal channel that was determined by the paleo-tidal current field and significantly different from the modern one, was in existence during the Holocene transgressive maxima and lasted until AD 1128. Following the capture of the Huaihe River in AD 1128 by the Yellow River, the paleo-Xiyang tidal channel was infilled with a large amount of river-derived sediments from AD 1128 to 1855, causing the emergence of some of the previously submerged tidal sand ridges. From AD 1855 to the present, the infilled paleo-Xiyang tidal channel has undergone scouring, resulting in its modern form. The modern Xiyang tidal channel continues to widen and deepen, due both to strong tidal current scouring and anthropogenic activities.