Boundary Sediments Research Articles

Constraints of nonseismic geophysical data on the deep geological structure of the Benxi iron-ore district, Liaoning, China

Abstract The Benxi area in Liaoning Province is one of the most important iron-ore districts in China. This study uses nonseismic geophysical data (in the form of gravity–magnetic–magnetotelluric data) and based on the section modeling method to model the deep, three-dimensional geological structure of the Benxi area. Based on the modeling results and deep geological structure characteristics, the Benxi area can be divided into three first-order deep geological tectonic units. A close relationship is between tectonic unit and iron-ore concentrations. First, high-quality iron-ore deposits occur within the tectonic boundary and sedimentary boundary zone of the Jiao–Liao–Ji Belt, reflects the protective effect of sedimentary cover on the iron-bearing formation. Second, enriched iron-ore deposits are mainly developed in Mesozoic granitic intrusion zone, reflects the hydrothermal leaching of silicon in host iron-bearing formations during magma intrusion. Thus, the findings of this study have important implications for future prospecting in the Benxi iron-ore district.

Detecting shifts of submarine sediment boundaries using side-scan mosaics and GIS analyses

Detecting changes of sediment boundaries on the seafloor is important for a better understanding of sediment dynamics and related impacts to benthic habitats. Side-scan sonars (SSS) perform more cost-effectively in shallow waters than other acoustic systems because of their larger swath widths, and the resolution of its images does not change with varying water depth. However, as they are generally towed behind the survey vessel, they tend to have lower positioning accuracy, which makes them unreliable for change detection analyses. In this study, we present a workflow that processes SSS data in a way that makes them fit for change detection analyses. To test the capacity of SSS mosaics for change detection, we used a free software called “Digital Shoreline Analysis System”, which was developed by the United States Geological Survey for ArcGIS version 10.4 onwards. The methods were applied in three areas in the Sylt Outer Reef, German Bight, North Sea. Our results showed that with appropriate processing, SSS mosaics could be used for change detection of sharp sediment boundaries. We found a common trend in the sediment distribution patterns of coarse sediments by monitoring the movement of their boundaries. The boundaries moved in northeast-southwest direction and boundary movements of less than 20 m were typically observed. The methods presented here are semi-automated, repeatable, and replicable, which has potential for wide-scale monitoring of sediment distribution patterns.

Petrographic study of oil migration on the example of Imilorskoye field (Kogalymsky petroleum region, Western Siberia)

Subject. This paper presents the results of studies of the mechanism of primary oil migration in the boundary sediments of the late Jurassic (Bazhenov formation)–early Cretaceous (Achimov pack) on the example of the well 431Р of the Imilor field. Materias and methods. Based on the working hypothesis of fluid fracturing as the main mechanism of primary oil migration, using optical-petrographic analysis, supplemented by geochemical research methods, systems of interconnected microcracks in the Tithonian-lower Berriasian and early Valanginian deposits were studied. Results. It is established that the investigated cracks occurred in three stages: 1) formation of primary sedimentary-lithogenetic fissures as a result of dehydration of clays in the stage of diagenesis and hydraulic fractures in the implementation of the Achimov of terrigenous rocks; 2) partial healing of cracks with secondary minerals in the catagenesis; 3) restoration of patency of the cracks in the generation of large amounts of free hydrocarbons of protopetroleum. It is shown that the migration of hydrocarbons generated by the formation occurred both within the Bazhenov formation itself and through a system of interconnected cracks in the contact zone of the Bazhenov formation with the Achimov formation. Conclusion. A detailed study of the mechanism of oil migration allows us to expand our understanding of the reservoir properties of the oil column, which in the future will allow us to forecast the reservoir properties of the Bazhenov formation including in the zones of anomalous sections (for example, in the Kogalym region).

Experimental study on near-bed flow turbulence of sinuous channel with downward seepage

The presence of a small seepage velocity in streams and rivers induces transfer of mass and momentum near the sediment boundary, causing bank failure and instability of hydraulic structures. This experimental study is intended to report near-bed hydrodynamics and morphological characteristics under the impact of downward seepage. A laboratory investigation was conducted in a sinuous rectangular alluvial channel with rigid sides and movable uniform sand bed. From the distribution of Reynolds shear stress (RSS), the transverse or radial motion of the sediment across the bend was identified. High values of RSS in the outer region relate to higher momentum flux, eroding the outer bend. The contribution probability of ejection and sweep events are highest in the bend region. For seepage, the contribution probability of the events has increased. Moreover, the altered flow with seepage affected the transport of sediment and caused noticeable modifications along the channel bed. With seepage, the erosion rate has been enhanced along the outer bend of the channel.

Seafloor sediment thickness beneath the VoiLA broad-band ocean-bottom seismometer deployment in the Lesser Antilles from P-to-S delay times

SUMMARYBroad-band ocean-bottom seismometer (OBS) deployments present an opportunity to investigate the seafloor sediment thickness, which is important for constraining sediment deposition, and is also useful for subsequent seismological analyses. The Volatile Recycling in the Lesser Antilles (VoiLA) project deployed 34 OBSs over the island arc, fore- and backarc of the Lesser Antilles subduction zone for 15 months from 2016 to 2017. Using the amplitudes and delay times of P-to-S (Ps) scattered waves from the conversion of teleseismic earthquake Pwaves at the crust–sediment boundary and pre-existing relationships developed for Cascadia, we estimate sediment thickness beneath each OBS. The delay times of the Ps phases vary from 0.20 ± 0.06 to 3.55 ± 0.70 s, generally increasing from north to south. Using a single-sediment and single-crystalline crust earth model in each case, we satisfactorily model the observations of eight OBSs. At these stations we find sediment thicknesses range from 0.43 ± 0.45 to 5.49 ± 3.23 km. To match the observations of nine other OBSs, layered sediment and variable thickness crust is required in the earth model to account for wave interference effects on the observed arrivals. We perform an inversion with a two-layer sediment and a single-layer crystalline crust in these locations finding overall sediment thicknesses of 1.75 km (confidence region: 1.45–2.02 km) to 7.93 km (confidence region: 6.32–11.05 km), generally thinner than the initial estimates based on the pre-existing relationships. We find agreement between our modelled velocity structure and the velocity structure determined from the VoiLA active-source seismic refraction experiment at the three common locations. Using the Ps values and estimates from the VoiLA refraction experiment, we provide an adjusted relationship between delay time and sediment equations for the Lesser Antilles. Our new relationship is ${{H}} = {{1.42}}{{\rm d}}{{{t}}^{ {1.44}}}$ , where H is sediment thickness in kilometres and dt is mean observed Ps delay time in seconds, which may be of use in other subduction zone settings with thick seafloor sediments.

Community structure of actively growing bacteria in a coastal fish-farming area.

In fish-farming areas, copious amounts of organic matter are released into the surrounding environment. Although it is well-known that bacterial community structures and activities are tightly coupled with organic conditions in the environment, actively growing bacteria (AGB) species that are responsible are still largely unknown. Here, we determined seasonal variations in the community structures of free-living and particle-attached AGB in surface and bottom seawater, and also in the easily resuspendable sediment boundary layer. Accordingly, we used bromodeoxyuridine (BrdU) magnetic bead immunocapture and PCR-denaturing gradient gel electrophoresis (BUMP-DGGE) analysis. Whereas overall bacterial communities in the resuspendable sediment were quite different from those of the free-living and particle-attached bacteria, the AGB community structures were similar among them. This result suggests that sediment resuspension in aquaculture environments functions as an organic source for bacteria in the water column, and that bacterial species contributing to the environmental capacity and carbon cycle are limited. We identified 25 AGB phylotypes, belonging to Alphaproteobacteria (Roseobacter clade, nine phylotypes), Gammaproteobacteria (five phylotypes), Deltaproteobacteria (one phylotype), Bacteroidetes (seven phylotypes), and Actinobacteria (three phylotypes). Among them, some AGB phylotypes appeared throughout the year with high frequency and were also identified in other coastal environments. This result suggests that these species are responsible for the environmental capacity and carbon cycle, and are key species in this fish-farming area, as well as other coastal environments.

New Prospects for Particle Characterization Using Analytical Centrifugation with Sector‐Shaped Centerpieces

AbstractAnalytical centrifugation (AC) has recently shown great potential for the accurate determination of particle size distributions. The well‐established LUMiSizer(R) is customized by a new design allowing for higher rotor speeds, improved thermal insulation, and measurement cell assembly. The latter enables sedimentation analysis of nanoparticles (NPs) in sector‐shaped centerpieces. The measurement window of AC experiments is assessed by the Peclet (Pe) number. It is shown that at low Pe numbers (0.7 < Pe < 30), sedimentation, and diffusion can be accurately and simultaneously analyzed from the sedimentation boundaries within one experiment. Moreover, sedimentation properties can be reliably determined up to Pe numbers of 4000. The thermal characteristic throughout the sedimentation analysis is validated by measuring polystyrene particles at elevated temperatures. Moreover, the performance of the setup is demonstrated by determining the sedimentation properties of SiO2 NPs at intermediate Pe numbers in excellent agreement with results from analytical ultracentrifugation experiments. Finally, for the first time, an accurate analysis of the core–shell properties of Au NPs via AC is presented. By combining the analysis of sedimentation and diffusional properties at low Pe numbers, the shell thickness of the stabilizer cetyltrimethylammonium bromide alongside the core diameter distribution of the Au NPs is determined.

Segregation and retention of As, potentially toxic metals, and organic pollutants in a reservoir from the Ohře River (the Czech Republic)

This work addresses the fates of elements from historical mining that peaked in the 16th (Ag, Cu, Pb, and Sn mining) and 20th (U) centuries, polycyclic aromatic hydrocarbons (PAHs), and polar pesticides in the Nechranice Dam Reservoir in the Ohře River. A steady fluvial input from secondary pollution (As, Cu, Pb, Sn, Zn) enabled the study of pollutant segregation during deposition and post-depositional migration in sediments. These elements are present in concentrations close to toxic levels for aquatic life, which will prevent the achievement of a favourable ecological status in the Ohře River, which is similar to many rivers in central and western Europe. The reservoir bottom morphology was acquired by sonar imaging. The sediments were then sampled by extracting 23 gravity cores to describe the distribution of pollution in sediments with sufficient reliability. The inflow delta was characterised by a sub-bottom profiler, aerial imaging, and photogrammetric modelling. X-ray fluorescence spectroscopy and chromatography were used for sediment analysis. The catchment-specific Hg and U pollution peaks provided local chemostratigraphic markers of the pre-dam/reservoir sediment boundary. The Sn-bearing pollutant particles were mostly retained immediately after entering the Nechranice Reservoir. Concentrations of Cu, Pb, and Zn are lower in the reservoir basin than in the inflow delta. The sediments of the reservoir basin with water depths > 20 m are enriched in the top layer with Mn species, which may be relevant for the fates of some pollutants. Arsenic shows a post-depositional enriched peak near the base of the Mn-enriched layer. The PAH concentrations normalised to the total organic carbon content (TOC) in the basin sediments are indirectly proportional to the Mn/Fe ratio, showing their oxidative degradation in the Mn-enriched strata. Our work reveals the important behaviour of pollutants in dam reservoirs, which has not yet been studied adequately to the relevance of the historical burdens in current fluvial systems, secondary fluvial pollution, and future reservoirs with historically polluted catchments. The inflow delta is a highly dynamic sedimentary system responding to changes in water level. The studied reservoir has behaved as a settling system with post-depositional chemical reactions relevant to pollutant fates. The retention of Mn(III,IV) oxides that is considerably enhanced by river damming might play a positive role in the degradation of modern organic pollutants. Arsenic in the sediments undergoes translocation to sharp subsurface peaks.

Biostratigraphy and determination of the K/Pg boundary in the upper Cretaceous sediments in northeast Kazerun, Fars zone (Zagros)

Biostratigraphy and determination of the K/Pg boundary in the upper Cretaceous sediments in northeast Kazerun, Fars zone (Zagros)

Cenomanian/Turonian oceanic anoxic event 2 in October oil field, central Gulf of Suez, Egypt

Gulf of Suez is one of the world most prolific Cretaceous and Miocene oil provinces in Egypt. In this basin the Late Cenomanian/Early Turonian organic rich limestone and shale sediments are referred to oceanic anoxic event 2 (OAE2). Two oil-cored wells (GS 197-2 and OCT-A8) have encountered the Late Cenomanian/Early Turonian Abu Qada Formation in October Field, central part of Gulf of Suez. The aim of this work is to pick the global Cenomanian/Turonian anoxic boundary in the subsurface sediments within the Gulf of Suez basin. Consequently, the core samples of the studied wells have been investigated in order to recognize the lithofacies, biostratigraphy, geochemistry and isotope content of upper Raha, Abu Qada and lower Wata formations. The microfacies association of anoxic middle to outer shelf marine were recognized. In addition, remarkable turnover and significant change in biostratigraphy and ichnological diversity and abundance were confirmed the abrupt change in oxidation and nutrition the Cenomanian-Turonian boundary. The recorded positive δ13C excursion (1.8‰) matched with maximum TOC value encountered to mark OAE2 as well as source rock maturity and potentiality of Abu Qada Formation. The neighboring exposed section of Abu Qada Formation in Gabal Nezzazat show similar isotopic and biostratigraphic characteristics that recorded in the studied wells. This work define the Cenomanian-Turonian OAE2 as material based chronostratigraphic surface boundary in Nezzazat Group from surface to subsurface integrated data to improve sequence stratigraphic interpretation of the heterogeneous Upper Cretaceous shallow marine reservoirs in Gulf of Suez.

Effect of the Mid-Carboniferous event on the diversity of brachiopods in the Middle and Southern Urals

Research subject. In this study, the distribution of brachiopods in the Mid-Carboniferous boundary (MCB) sediments in the Middle and Southern Urals was investigated with the aim of determining the influence of the global Serpukhovian-Bashkirian minor mass extinction event on the diversity of these benthic organisms. Materials and methods . Brachiopods distributed over the most complete carbonate sections of the West-Uralian (Brazhka, Sokol, Martyanovo, Askyn, Lakly), Magnitogorskian (Khudolaz, Kalinino, Bolshoy Kizil) and the East-Uralian (Beklenishchevo, Cave gully, Brod-Klyuchiki, “Uralnerud-1” quarry) megazons were studies. Results. It was established that the diversity of the Giganto-productus-Striatifera brachiopod association reduced during the Late Serpukhovian, with the extinction of its dominant taxa having occurred during the Early and Middle Carboniferous boundary. During the Syuranian time of the Bashkirian Age, the Middle-Late Carboniferous Choristites association was formed. Further, in the Akavassian time, the diversity of brachiopods was restored. The consequences of the described event affected mainly the taxa of the species and genus taxonomic rank, and, to a much lesser extent, those of the family rank. On the western slope of the Urals, the maximum regression was recorded at the top of the Striatifera shell-rock layer of the Lower Carboniferous Staroutkinskian regional substage. On the eastern slope of the Urals, the brachiopod diversity characterizing the event in question can be clearly seen in the Late Serpukhovian. This dynamics was also manifested in the lowermost Pennsylvanian; however, it was obscured by the activation of regional tectonic factors. Conclusion. In the Middle and Southern Urals, the Mid-Carboniferous minor mass extinction event is recognized according to the dynamics of the genus and species diversity of bra-chiopods in the deposits of different facies.

Enhancement of physicochemical and encapsulation stability of O1/W/O2 multiple nanoemulsions loaded with coenzyme Q10 or conjugated linoleic acid by incorporating polyphenolic extract.

Multiple O1/W/O2 nanoemulsions and O1/W nanoemulsions fortified with CLA or CoQ10 were produced using extra virgin olive or olive pomace oil and were also incorporated with polyphenols extracted from olive kernel to enhance their kinetic and chemical stability. They were prepared using a high-speed ultrasonic homogenizer. Specifically, nanoemulsions with 6 wt% lipid phase and 6 wt% non-ionic emulsifier (Tween 40) were produced and they demonstrated a droplet diameter >200 nm and high encapsulation stability during 30 days of storage at 4 °C or 25 °C. The incorporation of CLA or CoQ10 and polyphenolic compounds facilitated the homogenization of emulsions, reducing the droplet size and enhancing their chemical stability, and their bioactive retention values were >79%. O1/W/O2 nanoemulsions were produced using a mixture of non-ionic emulsifiers (Span 20 and Tween 40) and the O1/W enriched nanoemulsion as the dispersed phase. All multiple emulsions showed a bimodal droplet size distribution and Newtonian behavior while polyphenols facilitated their homogenization. Both vegetable oils resulted in samples with high kinetic and chemical stability; the bioactive retention values were found to be >80% at the end of 30 days of storage at 4 °C or 25 °C. Extra virgin olive oil resulted in more stable nanoemulsions in regards to kinetic and chemical stability at 4 °C, showing limited creaming and sedimentation boundary. Multiple nanoemulsions with the lowest initial droplet size presented the lowest droplet diameter growth and phase separation and the highest retention values. By comparing O1/W nanoemulsions and O1/W/O2 nanoemulsions, we noted that the reduction in the total phenolic content and antioxidant activity during storage was higher in the O1/W type. However, both delivery systems protected CLA and CoQ10 presenting high retention during storage. FTIR spectra before and after ultrasonic homogenization indicated that the sonication process did not significantly affect the lipid phase of O1/W/O2 nanoemulsions.

Wenlock-Ludlow boundary sediments on Chernov upli (Arctic region of Russia)

Wenlock-Ludlow boundary sediments on Chernov upli (Arctic region of Russia)

Paleogeography reconstruction of a multi-stage modified intra-cratonic basin—a case study from the Jurassic Ordos Basin, Western North China Craton

Post-depositional modification is commonly found in sedimentary basins, particularly in the eastern Tethys Tectonic Domain, and is related to special geological settings and evolution processes of the region. The Chinese continent is composed of numerous small-scale blocks that underwent intensive tectonic movements. Paleogeography reconstruction for a modified basin is fundamental for objectively understanding the basin dynamics and exploration of hydrocarbon, sandstone-type uranium deposits, and other mineral resources. As a large-scale intra-cratonic depression basin in the western part of the North China Craton (NCC), the Mesozoic Ordos Basin underwent multi-stage modification; as a result, only the western part was preserved. In this study, the paleogeography in Bathonian–Oxfordian ages of the Jurassic was reconstructed via integrated approaches including stratigraphic correlation, sedimentary facies analysis, provenance analysis, and fission track analysis. The original sedimentary boundary of the Ordos Basin during this period is approximately outlined. We determine that the northern and southern borders reach the Cenozoic Hetao Basin and the Cenozoic Weihe Basin, respectively, and that the eastern, northwestern, and southwestern borders lie to the west of Taihang Mountain, at the Langshan–Bayanhot Basin–Kexueshan, and to the west of Liupan Mountain, respectively. The original sedimentary extent of the Ordos Basin was almost twice that of the present-day residual basin. The evolution of this basin in the Mesozoic recorded the evolution and destruction processes of the NCC. The NCC shows that N–S- and W–E-trending compressional setting occurred during the Triassic and the Jurassic, respectively. The interactive activities of adjacent tectonic domains played a critical role in subsidence dynamics for the intra-cratonic Ordos Basin. This study provides further insights for exploration of hydrocarbon and sandstone-type uranium deposits in the Ordos Basin.

Structure of the Sediment and Crust in the Northeast North China Craton from Improved Sequential H-k Stacking Method

AbstractH-k stacking method is a standard receiver-function method to detect crustal thickness. But this method can not be applied in low-velocity sedimentary basins. To solve this problem, we propose an improved sequential H-k stacking method. The improved method needs two sequential stacks. Firstly, sediment structure is calculated using converted waves and multiples on the bottom boundary of sediments. Secondly, the sedimentary results are applied to calculate the crustal structure. Theoretical calculations and “recovery tests” indicate that the improved method can obtain accurate estimates in sedimentary basins. With the teleseismic data of North China Craton, the structure of sediments is thick in the depression and thin in the uplifted area, which is consistent with Deep Seismic Sounding results. The crust to the west of the North-South Gravity Lineament is relatively thick and has a low average Poisson ratio, whereas the east is relatively thin and has a high average Poisson ratio. This result and the structural feature from data regression imply that the eastern crust of the North China Craton has experienced wide extension, which reflect the crustal response to the severe destruction and deformation in that area compared to the western crust.

Modeling of Fluvial Processes for Braided Channel in Down Yangtze River, Part 2: Application to the Channel Regulation

A well validated two-dimensional surface numerical model for braided channel in down Yangtze River was used to analyse the effect of the channel regulation projects in Hechangzhou reach. Based on the different flow and sediment boundaries, the calculations were carried out to analyse the river bed evolution and the slit ratio under the impacts of two supposed projects. The results show that the subsequent submerged dikes nearby the existed one in left branch will be beneficial to the maintenance of the deep-water channel for right branch.

A matching method for integrating multiscale components to model elastic parameters

ABSTRACTSeismic inversion and reservoir identification are complicated problems with integrated data sets and need a velocity or density model to ensure the stability of the results. However, an elastic parameter model, such as velocity or density, is difficult to obtain with high precision by conventional migration or interpolation, especially during the early exploration stage, which contains few available logging data. The kriging method has proved to be an effective technique for mineral exploration and petroleum geophysics, and has led to a series of expansive techniques in earth science. In this paper, we proposed a new matching method, base value compensation (BVC), for integrating multiscale data sets into model elastic parameters. Considering the variety of original information, we used multiple constrain cokriging for three types of data set at different scales. These three data sets come from logging, seismic attributes and sedimentary facies information. The P-wave velocity model is stable and more representative of the subsurface condition, but we found that this method produces few points with anomalous values in the density model. Those abnormal points cause substantial loss of geological detail at sedimentary boundaries. In most modelling methods, this shortcoming is due to the fact that these three input parameters have significantly different properties. The proposed method can effectively solve this problem by matching the input data sets at a similar observational scale before modelling. We demonstrated this method using a case study in the South China Sea. The decrease in abnormal points in the final modelling results verifies the effectiveness of BVC.

Influence of Temperature Variability in the Near-Bottom Layer on the Results of Geothermal Measurements in the Kvitøya Trough (Barents Sea)

According to a study of the thermal variability of the water column in the Kvitoya trough (northern part of the Barents Sea), substantial water temperature fluctuations in the near-bottom layer were found, both seasonal and interannual, which affect the temperature distribution in the upper layer of bottom sediments and, therefore, the results of geothermal measurements. The contribution of temperature fluctuations at the water–sediment boundary to the values of conductive heat flow measured during cruise 25 of the R/V Akademik Nikolaj Strakhov was calculated. Endogenous heat flow was determined.

Titanium local coordination environments in Cretaceous–Paleogene and Devonian–Carboniferous boundary sediments as a possible marker for large meteorite impact

The local coordination environments of Ti in Cretaceous–Paleogene (K–Pg) from Stevns Klint and Devonian–Carboniferous (D–C) boundary from western part of Cat Co Beach on Cat Ba Island sediments are studied by K-edge X-ray absorption fine structure (XAFS) in order to provide local atomic information by X-ray absorption near edge structure (XANES) and coordination environments by extended X-ray absorption fine structure (EXAFS). Ti K-edge XAFS spectra in bulk part of K–Pg and D–C boundary sediments are compared with those of reference materials such as TiO2 (rutile, anatase and brookite polymorph), CaTiO3, MgTiO3, SrTiO3, PbTiO3, moldavite-brownish, moldavite-green, suevite from Ries crater, impactite, obsidian and Kilauea volcanic glass. The shapes of XANES and EXAFS spectra in K–Pg sediments are similar to those in suevite. Suevite was formed under meteorite impact and its glass component was formed under high temperature and high pressure. Similarities of XANES and EXAFS between K–Pg sediments and suevite indicate that formation process of K–Pg sediments is related to a meteorite impact event. On the other hand, the shape of XANES spectrum in D–C sediments is similar to those in anatase and obsidian. However, the shape of EXAFS spectra in D–C sediments is similar to those in obsidian, rather than anatase. Coordination environments of Ti in D–C sediments suggest that the original glass-like local environments were changed to anatase-like local environments by devitrification. This leads to the conclusion that the analysis of the atomic coordination environments of Ti in boundary sediments can in principle be used as a marker of large meteorite impact, though this Ti local environmental information is actually lost due to the devitrification phenomenon to anatase by quenching process or long-time diagenesis. This may be compensated by the XAFS analysis of Zr because local coordination environments of Zr in same analytical point of K–Pg sediments were not affected by diagenesis (Tobase et al., J Miner Petrol Sci 110:88–91, 2015a).

Undrained shear strength evaluation for hydrate-bearing sediment overlying strata in the Shenhu area, northern South China Sea

The undrained shear strength of shallow strata is a critical parameter for safety design in deep-water operations. In situ piezocone penetration tests (CPTU) and laboratory experiments are performed at Site W18-19 in the Shenhu area, northern South China Sea, where China’s first marine hydrate exploitation operation is due to be located. The validation of the undrained shear strength prediction model based on CPTU parameters. Different laboratory tests, including pocket penetrometer, torvane, miniature vane and unconsolidated undrained triaxial tests, are employed to solve empirical cone coefficients by statistical and mathematical methods. Finally, an optimized model is proposed to describe the longitudinal distribution of undrained shear strength in calcareous clay strata in the Shenhu area. Research results reveal that average empirical cone coefficients based on total cone resistance, effective resistance, and excess-pore pressure are 13.8, 4.2 and 14.4, respectively. The undrained shear strength prediction model shows a good fit with the laboratory results only within specific intervals based on their compaction degree and gas-bearing conditions. The optimized prediction model in piecewise function format can be used to describe the longitudinal distribution of the undrained shear strength for calcareous clay within all depth intervals from the mud-line to the upper boundary of hydrate-bearing sediments (HBS). The optimized prediction result indicates that the effective cone resistance model is suitable for very soft to firm calcareous clays, the excess-pore pressure model can depict the undrained shear strength for firm to very stiff but gas-free clays, while the total cone resistance model is advantageous for evaluating the undrained shear strength for very stiff and gassy clays. The optimized model in piecewise function format can considerably improve the adaptability of empirical models for calcareous clay in the Shenhu area. These results are significant for safety evaluations of proposed hydrate exploitation projects.