2024 Vol. 43, No. 2
Display Method:
2024, 43(2): .
Abstract:
2024, 43(2): 1-10.
doi: 10.1007/s13131-023-2147-0
Abstract:
Composite analyses were performed in this study to reveal the difference in spring precipitation over southern China during multiyear La Niña events during 1901 to 2015. It was found that there is significantly below-normal precipitation during the first boreal spring, but above-normal precipitation during the second year. The difference in spring precipitation over southern China is correlative to the variation in western North Pacific anomalous cyclone (WNPC), which can in turn be attributed to the different sea surface temperature anomaly (SSTA) over the Tropical Pacific. The remote forcing of negative SSTA in the equatorial central and eastern Pacific and the local air-sea interaction in the western North Pacific are the usual causes of WNPC formation and maintenance. SSTA in the first spring is stronger than those in the second spring. As a result, the intensity of WNPC in the first year is stronger, which is more likely to reduce the moisture in southern China by changing the moisture transport, leading to prolonged precipitation deficits over southern China. However, the tropical SSTA signals in the second year are too weak to induce the formation and maintenance of WNPC and the below-normal precipitation over southern China. Thus, the variation in tropical SSTA signals between two consecutive springs during multiyear La Niña events leads to obvious differences in the spatial pattern of precipitation anomaly in southern China by causing the different WNPC response.
Composite analyses were performed in this study to reveal the difference in spring precipitation over southern China during multiyear La Niña events during 1901 to 2015. It was found that there is significantly below-normal precipitation during the first boreal spring, but above-normal precipitation during the second year. The difference in spring precipitation over southern China is correlative to the variation in western North Pacific anomalous cyclone (WNPC), which can in turn be attributed to the different sea surface temperature anomaly (SSTA) over the Tropical Pacific. The remote forcing of negative SSTA in the equatorial central and eastern Pacific and the local air-sea interaction in the western North Pacific are the usual causes of WNPC formation and maintenance. SSTA in the first spring is stronger than those in the second spring. As a result, the intensity of WNPC in the first year is stronger, which is more likely to reduce the moisture in southern China by changing the moisture transport, leading to prolonged precipitation deficits over southern China. However, the tropical SSTA signals in the second year are too weak to induce the formation and maintenance of WNPC and the below-normal precipitation over southern China. Thus, the variation in tropical SSTA signals between two consecutive springs during multiyear La Niña events leads to obvious differences in the spatial pattern of precipitation anomaly in southern China by causing the different WNPC response.
2024, 43(2): 11-22.
doi: 10.1007/s13131-023-2223-5
Abstract:
The wave-induced liquefaction of seabed is responsible for causing damage to marine structures. Particle composition and consolidation degree are the key factors affecting the pore water pressure response and liquefaction behavior of the seabed under wave action. The present study conducted wave flume experiments on silt and silty fine sand beds with varying particle compositions. Furthermore, a comprehensive analysis of the differences and underlying reasons for liquefaction behavior in two different types of soil was conducted from both macroscopic and microscopic perspectives. The experimental results indicate that the silt bed necessitates a lower wave load intensity to attain the liquefaction state in comparison to the silty fine sand bed. Additionally, the duration and development depth of liquefaction are greater in the silt bed. The dissimilarity in liquefaction behavior between the two types of soil can be attributed to the variation in their permeability and plastic deformation capacity. The permeability coefficient and compression modulus of silt are lower than those of silty fine sand. Consequently, silt is more prone to the accumulation of pore pressure and subsequent liquefaction under external loading. Prior research has demonstrated that silt beds with varying consolidation degrees exhibit distinct initial failure modes. Specifically, a dense bed undergoes shear failure, whereas a loose bed experiences initial liquefaction failure. This study utilized discrete element simulation to examine the microscopic mechanisms that underlie this phenomenon.
The wave-induced liquefaction of seabed is responsible for causing damage to marine structures. Particle composition and consolidation degree are the key factors affecting the pore water pressure response and liquefaction behavior of the seabed under wave action. The present study conducted wave flume experiments on silt and silty fine sand beds with varying particle compositions. Furthermore, a comprehensive analysis of the differences and underlying reasons for liquefaction behavior in two different types of soil was conducted from both macroscopic and microscopic perspectives. The experimental results indicate that the silt bed necessitates a lower wave load intensity to attain the liquefaction state in comparison to the silty fine sand bed. Additionally, the duration and development depth of liquefaction are greater in the silt bed. The dissimilarity in liquefaction behavior between the two types of soil can be attributed to the variation in their permeability and plastic deformation capacity. The permeability coefficient and compression modulus of silt are lower than those of silty fine sand. Consequently, silt is more prone to the accumulation of pore pressure and subsequent liquefaction under external loading. Prior research has demonstrated that silt beds with varying consolidation degrees exhibit distinct initial failure modes. Specifically, a dense bed undergoes shear failure, whereas a loose bed experiences initial liquefaction failure. This study utilized discrete element simulation to examine the microscopic mechanisms that underlie this phenomenon.
2024, 43(2): 23-33.
doi: 10.1007/s13131-024-2290-2
Abstract:
At present, the main controlling factors of helium accumulation is one of the key scientific problems restricting the exploration and development of helium reservoir. In this paper, based on the calculation results of He generation rate and the geochemical characteristics of the produced gas, both the similarities and differences between natural gas and He resources in the Bohai Bay, Ordos and the surrounding Songliao Basin are compared and analyzed, discussing the main controlling factors of helium resources in the three main petroliferous basins of the North China Craton. It is found that the three basins of Bohai Bay, Ordos and Songliao have similar characteristics of source rocks, reservoirs and cap rocks, that’s why their methane resource characteristics are essentially the same. The calculated 4He generation per cubic metamorphic crystalline basement in the three basins is roughly equivalent, which is consistent with the measured He resources, and it is believed that the 4He of radiogenic from the crust is the main factor controlling the overall He accumulation in the three basins; there is almost no contribution of the mantle-derived CH4, which suggests that the transport and uplift of mantle-derived 3He carried by the present-day magmatic activities along the deep-large faults is not the main reason for the mantle-derived 3He mixing in the basins. Combined with the results of regional volcanic and geophysical studies, it is concluded that under the background of the destruction of North China Craton, magma intrusion carried a large amount of mantle-derived material and formed basic volcanic rocks in the Bohai Bay Basin and Songliao Basin, which replenished mantle-derived 3He for the interior of the basins, and that strong seismic activities in and around the basins also promoted the upward migration of mantle source 3He. This study suggests that the tectonic zone with dense volcanic rocks in the Cenozoic era and a high incidence of historical strong earthquakes history may be a potential area for helium resource exploration.
At present, the main controlling factors of helium accumulation is one of the key scientific problems restricting the exploration and development of helium reservoir. In this paper, based on the calculation results of He generation rate and the geochemical characteristics of the produced gas, both the similarities and differences between natural gas and He resources in the Bohai Bay, Ordos and the surrounding Songliao Basin are compared and analyzed, discussing the main controlling factors of helium resources in the three main petroliferous basins of the North China Craton. It is found that the three basins of Bohai Bay, Ordos and Songliao have similar characteristics of source rocks, reservoirs and cap rocks, that’s why their methane resource characteristics are essentially the same. The calculated 4He generation per cubic metamorphic crystalline basement in the three basins is roughly equivalent, which is consistent with the measured He resources, and it is believed that the 4He of radiogenic from the crust is the main factor controlling the overall He accumulation in the three basins; there is almost no contribution of the mantle-derived CH4, which suggests that the transport and uplift of mantle-derived 3He carried by the present-day magmatic activities along the deep-large faults is not the main reason for the mantle-derived 3He mixing in the basins. Combined with the results of regional volcanic and geophysical studies, it is concluded that under the background of the destruction of North China Craton, magma intrusion carried a large amount of mantle-derived material and formed basic volcanic rocks in the Bohai Bay Basin and Songliao Basin, which replenished mantle-derived 3He for the interior of the basins, and that strong seismic activities in and around the basins also promoted the upward migration of mantle source 3He. This study suggests that the tectonic zone with dense volcanic rocks in the Cenozoic era and a high incidence of historical strong earthquakes history may be a potential area for helium resource exploration.
2024, 43(2): 34-42.
doi: 10.1007/s13131-023-2226-2
Abstract:
To better understand the community patterns mediated by connectivity in artificial reefs of coastal areas, it is necessary to understand the distribution and coexistence of organisms with artificial reefs area and adjacent waters. This study was conducted to examine main catches assemblages collected by trawls in Haizhou Bay, which included five habitats: the artificial reef area (AR), aquaculture area (AA), natural area (NA), estuary area (EA) and comprehensive effect area (CEA). The result shows that the total abundances of species in the five habitats were highly different (univariate PERMANOVA: P = 0.001, n = 24), but some species were also unique in their habitat (e.g. Scapharca subcrenata and Glossaulax didyma in AA). The body size distribution of specific species between habitats are different. For Collichthys lucidus, their body size in AR (14.63 cm ± 1.64 cm) and EA (14.3 cm ± 0.85 cm) is higher than that in NA (10.65 cm ± 1.64 cm), CEA (11.28 cm ± 1.85 cm) and AA (12.1 cm ± 0.43 cm), which indicates the potential connection from AR to EA mediated by their adult population. We concluded that artificial reefs in AR can be considered key components that have the ability to support species assemblages in adjacent habitats. This study has implications for the conservation and monitoring of species assemblages in coastal areas in terms of that artificial reefs can be applied in different stages of habitat protection implementation and in different combinations of scenarios.
To better understand the community patterns mediated by connectivity in artificial reefs of coastal areas, it is necessary to understand the distribution and coexistence of organisms with artificial reefs area and adjacent waters. This study was conducted to examine main catches assemblages collected by trawls in Haizhou Bay, which included five habitats: the artificial reef area (AR), aquaculture area (AA), natural area (NA), estuary area (EA) and comprehensive effect area (CEA). The result shows that the total abundances of species in the five habitats were highly different (univariate PERMANOVA: P = 0.001, n = 24), but some species were also unique in their habitat (e.g. Scapharca subcrenata and Glossaulax didyma in AA). The body size distribution of specific species between habitats are different. For Collichthys lucidus, their body size in AR (14.63 cm ± 1.64 cm) and EA (14.3 cm ± 0.85 cm) is higher than that in NA (10.65 cm ± 1.64 cm), CEA (11.28 cm ± 1.85 cm) and AA (12.1 cm ± 0.43 cm), which indicates the potential connection from AR to EA mediated by their adult population. We concluded that artificial reefs in AR can be considered key components that have the ability to support species assemblages in adjacent habitats. This study has implications for the conservation and monitoring of species assemblages in coastal areas in terms of that artificial reefs can be applied in different stages of habitat protection implementation and in different combinations of scenarios.
2024, 43(2): 43-57.
doi: 10.1007/s13131-023-2264-9
Abstract:
High-resolution sea-level data and high-precision dating of corals in the northern South China Sea (SCS) during the Holocene provide a reference and historical background for current and future sea-level changes and a basis for scientific assessment of the evolutionary trend of coral reefs in the SCS. Although sporadic studies have been performed around Hainan Island in the northern SCS, the reconstructed sea level presents different values or is controversial because the indicative meaning of the sea-level indicators were neither quantified nor uniform criteria. Here, we determined the quantitative relationship between modern living coral and sea level by measuring the top surfaces of 27 live Porites corals from the inner reef flat along the east coast of Hainan Island and assessed the accuracy of results obtained using coral as sea-level indicators. Additionally, three in situ fossil Porites corals were analyzed based on elevation measurements, digital X-ray radiography, and U-Th dating. The survey results showed that the indicative meanings for the modern live Porites corals is (146.09 ± 8.35) cm below the mean tide level (MTL). It suggested that their upward growth limit is constrained by the sea level, and the lowest low water is the highest level of survival for the modern live Porites corals. Based on the newly defined indicative meanings, 6 new sea-level index points (SLIPs) were obtained and 19 published SLIPs were recalculated. Those SLIPs indicated a relative sea level fluctuation between (227.7 ± 9.8) cm to (154.88 ± 9.8) cm MTL between (5 393 ± 25) cal a BP and (3 390 ± 12) cal a BP, providing evidences of the Mid-Holocene sea-level highstand in the northern SCS. Besides that, our analysis demonstrated that different sea-level histories may be produced based on different indicative meanings or criteria. The dataset of 276 coral U-Th ages indicates that coral reef development in the northern SCS comprised the initial development, boom growth, decline, and flourishing development again. A comparison with regional records indicated that synergistic effects of climatic and environmental factors were involved in the development of coral reefs in the northern SCS. Thus, the cessation of coral reef development during the Holocene in the northern SCS was probably associated with the dry and cold climate in South China, as reflected in the synchronous weakening of the ENSO and East Asian summer monsoon induced by the reduction of the 65°N summer insolation, which forced the migration of the Intertropical Convergence Zone.
High-resolution sea-level data and high-precision dating of corals in the northern South China Sea (SCS) during the Holocene provide a reference and historical background for current and future sea-level changes and a basis for scientific assessment of the evolutionary trend of coral reefs in the SCS. Although sporadic studies have been performed around Hainan Island in the northern SCS, the reconstructed sea level presents different values or is controversial because the indicative meaning of the sea-level indicators were neither quantified nor uniform criteria. Here, we determined the quantitative relationship between modern living coral and sea level by measuring the top surfaces of 27 live Porites corals from the inner reef flat along the east coast of Hainan Island and assessed the accuracy of results obtained using coral as sea-level indicators. Additionally, three in situ fossil Porites corals were analyzed based on elevation measurements, digital X-ray radiography, and U-Th dating. The survey results showed that the indicative meanings for the modern live Porites corals is (146.09 ± 8.35) cm below the mean tide level (MTL). It suggested that their upward growth limit is constrained by the sea level, and the lowest low water is the highest level of survival for the modern live Porites corals. Based on the newly defined indicative meanings, 6 new sea-level index points (SLIPs) were obtained and 19 published SLIPs were recalculated. Those SLIPs indicated a relative sea level fluctuation between (227.7 ± 9.8) cm to (154.88 ± 9.8) cm MTL between (5 393 ± 25) cal a BP and (3 390 ± 12) cal a BP, providing evidences of the Mid-Holocene sea-level highstand in the northern SCS. Besides that, our analysis demonstrated that different sea-level histories may be produced based on different indicative meanings or criteria. The dataset of 276 coral U-Th ages indicates that coral reef development in the northern SCS comprised the initial development, boom growth, decline, and flourishing development again. A comparison with regional records indicated that synergistic effects of climatic and environmental factors were involved in the development of coral reefs in the northern SCS. Thus, the cessation of coral reef development during the Holocene in the northern SCS was probably associated with the dry and cold climate in South China, as reflected in the synchronous weakening of the ENSO and East Asian summer monsoon induced by the reduction of the 65°N summer insolation, which forced the migration of the Intertropical Convergence Zone.
2024, 43(2): 58-66.
doi: 10.1007/s13131-023-2222-6
Abstract:
Based on high-tide shoreline data extracted from 87 Landsat satellite images from 1986 to 2019 as well as using the linear regression rate and performing a Mann-Kendall (M–K) trend test, this study analyzes the linear characteristics and nonlinear behavior of the medium- to long-term shoreline evolution of Jinghai Bay, eastern Guangdong Province. In particular, shoreline rotation caused by a shore-normal coastal structure is emphasized. The results show that the overall shoreline evolution over the past 30 years is characterized by erosion on the southwest beach, with an average erosion rate of 3.1 m/a, and significant accretion on the northeast beach, with an average accretion rate of 5.6 m/a. Results of the M–K trend test indicate that significant shoreline changes occurred in early 2006, which can be attributed to shore-normal engineering. Prior to that engineering construction, the shorelines are slightly eroded, where the average erosion rate is 0.7 m/a. However, after shore-normal engineering is performed, the shoreline is characterized by significant erosion (3.2 m/a) on the southwest beach and significant accretion (8.5 m/a) on the northeast beach, thus indicating that the shore-normal engineering at the updrift headland contributes to clockwise shoreline rotation. Further analysis shows that the clockwise shoreline rotation is promoted not only by longshore sediment transport processes from southwest to northeast, but also by cross-shore sediment transport processes. These findings are crucial for beach erosion risk management, coastal disaster zoning, regional sediment budget assessments, and further observations and predictions of beach morphodynamics.
Based on high-tide shoreline data extracted from 87 Landsat satellite images from 1986 to 2019 as well as using the linear regression rate and performing a Mann-Kendall (M–K) trend test, this study analyzes the linear characteristics and nonlinear behavior of the medium- to long-term shoreline evolution of Jinghai Bay, eastern Guangdong Province. In particular, shoreline rotation caused by a shore-normal coastal structure is emphasized. The results show that the overall shoreline evolution over the past 30 years is characterized by erosion on the southwest beach, with an average erosion rate of 3.1 m/a, and significant accretion on the northeast beach, with an average accretion rate of 5.6 m/a. Results of the M–K trend test indicate that significant shoreline changes occurred in early 2006, which can be attributed to shore-normal engineering. Prior to that engineering construction, the shorelines are slightly eroded, where the average erosion rate is 0.7 m/a. However, after shore-normal engineering is performed, the shoreline is characterized by significant erosion (3.2 m/a) on the southwest beach and significant accretion (8.5 m/a) on the northeast beach, thus indicating that the shore-normal engineering at the updrift headland contributes to clockwise shoreline rotation. Further analysis shows that the clockwise shoreline rotation is promoted not only by longshore sediment transport processes from southwest to northeast, but also by cross-shore sediment transport processes. These findings are crucial for beach erosion risk management, coastal disaster zoning, regional sediment budget assessments, and further observations and predictions of beach morphodynamics.
2024, 43(2): 67-82.
doi: 10.1007/s13131-023-2262-y
Abstract:
The Oligocene Zhuhai sandstones are significant reservoirs for hydrocarbons in the Baiyun Sag, South China Sea. For effective appraisal, exploration and exploitation of such a deep-water hydrocarbon sandstone, samples of five wells from depths of 850 m to 3000 m were studied. A series of comprehensive petrographic and geochemical analyses were performed to unravel the diagenetic features and their impact on the reservoir quality. Petrographically, the sandstones are dominated by feldspathic litharenites and lithic arenites with fine to medium grain sizes and moderate to good sorting. The reservoir quality varies greatly with a range of porosity from 0.2% to 36.1% and permeability from 0.016 ×10–3 μm2 to 4301 ×10–3 μm2, which is attributed to complex diagenetic evolution related to sedimentary facies; these include compaction, cementation of calcite, dolomite, siderite and framboidal pyrite in eogenetic stage; further compaction, feldspar dissolution, precipitation of ferrocalcite and ankerite, quartz cements, formation of kaolinite and its illitization, precipitation of albite and nodular pyrite, as well as hydrocarbon charge in mesogenetic stage. The dissolution of feldspar and illitization of kaolinite provide internal sources for the precipitation of quartz cement, while carbonate cements are derived from external sources related to interbedded mudstones and deep fluid. Compaction is the predominant factor in reducing the total porosity, followed by carbonate cementation that leads to strong heterogeneity. Feldspar dissolution and concomitant quartz and clay cementation barely changes the porosity but significantly reduces the permeability. The high-quality reservoirs can be concluded as medium-grained sandstones lying in the central parts of thick underwater distributary channel sandbodies (>2 m) with a high content of detrital quartz but low cement.
The Oligocene Zhuhai sandstones are significant reservoirs for hydrocarbons in the Baiyun Sag, South China Sea. For effective appraisal, exploration and exploitation of such a deep-water hydrocarbon sandstone, samples of five wells from depths of 850 m to 3000 m were studied. A series of comprehensive petrographic and geochemical analyses were performed to unravel the diagenetic features and their impact on the reservoir quality. Petrographically, the sandstones are dominated by feldspathic litharenites and lithic arenites with fine to medium grain sizes and moderate to good sorting. The reservoir quality varies greatly with a range of porosity from 0.2% to 36.1% and permeability from 0.016 ×10–3 μm2 to 4301 ×10–3 μm2, which is attributed to complex diagenetic evolution related to sedimentary facies; these include compaction, cementation of calcite, dolomite, siderite and framboidal pyrite in eogenetic stage; further compaction, feldspar dissolution, precipitation of ferrocalcite and ankerite, quartz cements, formation of kaolinite and its illitization, precipitation of albite and nodular pyrite, as well as hydrocarbon charge in mesogenetic stage. The dissolution of feldspar and illitization of kaolinite provide internal sources for the precipitation of quartz cement, while carbonate cements are derived from external sources related to interbedded mudstones and deep fluid. Compaction is the predominant factor in reducing the total porosity, followed by carbonate cementation that leads to strong heterogeneity. Feldspar dissolution and concomitant quartz and clay cementation barely changes the porosity but significantly reduces the permeability. The high-quality reservoirs can be concluded as medium-grained sandstones lying in the central parts of thick underwater distributary channel sandbodies (>2 m) with a high content of detrital quartz but low cement.
2024, 43(2): 83-93.
doi: 10.1007/s13131-023-2198-2
Abstract:
As one of the micro-blocks dispersed in the South China Sea (SCS), the basement of the Xisha Islands has rarely been drilled because of the thick overlying Cenozoic sediments, which has led to a confused understanding of the pre-Cenozoic basement of the Xisha Islands. Well CK-1, a kilometer-scale major scientific drill in the Xisha Islands in the northwestern SCS, penetrated thick reefal limestone (0–888.4 m) and the underlying basement rocks (888.4–901.4 m). In this study, we present the zircon U-Pb ages of basement basaltic pyroclastic rocks from Well CK-1 in the Xisha Islands of the northwestern SCS to investigate the basement nature of the Xisha micro-block. The basement of Well CK-1 consists of basaltic pyroclastic rocks on the seamount. The zircon grains yielded apparent ages ranging from ca. 2 138.9 Ma to ca. 36 Ma. The old group of zircon grains from Well CK-1 was considered to be inherited zircons. Two Cenozoic zircons gave a weighted mean 206Pb/238U age of (36.3 ± 1.1) Ma, Mean Squared Weighted Deviations (MSWD) = 1.2, which may represent the maximum age of the volcano eruption. The Yanshanian inherited zircons (116.9–105.7 Ma and 146.1–130.2 Ma) from Well CK-1 are consistent with the zircons from Well XK-1, indicating that the basement of Chenhang Island may be similar to that of Well XK-1. We propose that the Xisha micro-block may have developed on a uniform Late Jurassic metamorphic crystalline basement, intruded by Cretaceous granitic magma.
As one of the micro-blocks dispersed in the South China Sea (SCS), the basement of the Xisha Islands has rarely been drilled because of the thick overlying Cenozoic sediments, which has led to a confused understanding of the pre-Cenozoic basement of the Xisha Islands. Well CK-1, a kilometer-scale major scientific drill in the Xisha Islands in the northwestern SCS, penetrated thick reefal limestone (0–888.4 m) and the underlying basement rocks (888.4–901.4 m). In this study, we present the zircon U-Pb ages of basement basaltic pyroclastic rocks from Well CK-1 in the Xisha Islands of the northwestern SCS to investigate the basement nature of the Xisha micro-block. The basement of Well CK-1 consists of basaltic pyroclastic rocks on the seamount. The zircon grains yielded apparent ages ranging from ca. 2 138.9 Ma to ca. 36 Ma. The old group of zircon grains from Well CK-1 was considered to be inherited zircons. Two Cenozoic zircons gave a weighted mean 206Pb/238U age of (36.3 ± 1.1) Ma, Mean Squared Weighted Deviations (MSWD) = 1.2, which may represent the maximum age of the volcano eruption. The Yanshanian inherited zircons (116.9–105.7 Ma and 146.1–130.2 Ma) from Well CK-1 are consistent with the zircons from Well XK-1, indicating that the basement of Chenhang Island may be similar to that of Well XK-1. We propose that the Xisha micro-block may have developed on a uniform Late Jurassic metamorphic crystalline basement, intruded by Cretaceous granitic magma.
2024, 43(2): 94-110.
doi: 10.1007/s13131-023-2218-2
Abstract:
The southwest Lahad Datu felsic rocks were previously thought to have formed in the late Triassic as part of the microcontinental crystalline basement. Based on U-Pb ages, geochemistry, and the Hf isotopes of zircon from the southeastern Sabah gabbro and granite, in this study, the tectonic properties of the Sabah area during the Triassic were investigated. The weighted average U-Pb zircon ages of the gabbro and granite samples were determined to be (230.9 ± 2.5)Ma and (207.1 ± 3.3)Ma, respectively. The granite had SiO2 contents of 66.54%–79.47%, low TiO2 contents of 0.08%–0.3%, Al2O3 contents of 10.97%–16.22%, Na2O contents of 5.91%–6.39%, and low K2O contents of 0.15%–0.65%. The chondrite-normalized rare earth element (REE) patterns exhibit light REE enrichment, with right-sloping curves. The primitive mantle-normalized trace element spider diagrams exhibit Th, U, La, Sr, and Zr enrichment and Nb, Ta, P and Ti depletions, i.e., the geochemical characteristics of typical island arc igneous rocks. The tectonic discriminant diagram indicates that the granite is a volcanic arc granite. The Hf isotopic analysis of gabbro zircon revealed that the zircons have εHf(t) values of 12.08–16.24 (mean of 14.32) and two-stage model ages (tDM2) of 223–491 Ma (mean of 347 Ma). This indicates that the diagenetic magma of the gabbro was mainly derived from melting of newly formed crustal materials. The ophiolite in southeast Sabah has existed since the early Late Triassic. The crystalline basement granite in southeastern Sabah was emplaced lasted from late Triassic to early Cretaceous. Based on previous studies and global plate reconstruction models, it is speculated that the southeastern Sabah granite may have been formed in an island arc setting, i.e., where the oceanic crust of the Paleo-Tethys Ocean collided with the oceanic crust of the Panthalassa Ocean.
The southwest Lahad Datu felsic rocks were previously thought to have formed in the late Triassic as part of the microcontinental crystalline basement. Based on U-Pb ages, geochemistry, and the Hf isotopes of zircon from the southeastern Sabah gabbro and granite, in this study, the tectonic properties of the Sabah area during the Triassic were investigated. The weighted average U-Pb zircon ages of the gabbro and granite samples were determined to be (230.9 ± 2.5)Ma and (207.1 ± 3.3)Ma, respectively. The granite had SiO2 contents of 66.54%–79.47%, low TiO2 contents of 0.08%–0.3%, Al2O3 contents of 10.97%–16.22%, Na2O contents of 5.91%–6.39%, and low K2O contents of 0.15%–0.65%. The chondrite-normalized rare earth element (REE) patterns exhibit light REE enrichment, with right-sloping curves. The primitive mantle-normalized trace element spider diagrams exhibit Th, U, La, Sr, and Zr enrichment and Nb, Ta, P and Ti depletions, i.e., the geochemical characteristics of typical island arc igneous rocks. The tectonic discriminant diagram indicates that the granite is a volcanic arc granite. The Hf isotopic analysis of gabbro zircon revealed that the zircons have εHf(t) values of 12.08–16.24 (mean of 14.32) and two-stage model ages (tDM2) of 223–491 Ma (mean of 347 Ma). This indicates that the diagenetic magma of the gabbro was mainly derived from melting of newly formed crustal materials. The ophiolite in southeast Sabah has existed since the early Late Triassic. The crystalline basement granite in southeastern Sabah was emplaced lasted from late Triassic to early Cretaceous. Based on previous studies and global plate reconstruction models, it is speculated that the southeastern Sabah granite may have been formed in an island arc setting, i.e., where the oceanic crust of the Paleo-Tethys Ocean collided with the oceanic crust of the Panthalassa Ocean.
2024, 43(2): 111-119.
doi: 10.1007/s13131-023-2195-5
Abstract:
The tephra layers in multiple sediment cores from the offshore region of the Mahanadi basin in the northern Bay of Bengal were investigated for possible volcanic sources. The glass shards from those tephra layers were studied for size distribution, texture, and elemental geochemistry to establish chronostratigraphic markers for regional and global Quaternary correlation. The textural features of fine-grained (silty) volcanic glasses suggest the distal source of these tephra deposits. Major element composition with elevated SiO2 contents ranging between 75%–76% and dominance of K2O (> 4.5%) over CaO (< 0.9%) suggest ashes have originated from siliceous rhyolitic melts, similar to the petrographic composition of tephra from the Toba volcano. The bulk trace element compositions of the same glass shards were comparable with those reported in the youngest Toba tephra reported elsewhere. Likewise, the LREE-dominated chondrite normalized REE profiles of tephra from the Mahanadi basin closely resemble the characteristic REE patterns in Toba ash from other parts of the Indian Ocean and thus confirmed the contribution of the youngest Toba super-eruption for this ash layers.
The tephra layers in multiple sediment cores from the offshore region of the Mahanadi basin in the northern Bay of Bengal were investigated for possible volcanic sources. The glass shards from those tephra layers were studied for size distribution, texture, and elemental geochemistry to establish chronostratigraphic markers for regional and global Quaternary correlation. The textural features of fine-grained (silty) volcanic glasses suggest the distal source of these tephra deposits. Major element composition with elevated SiO2 contents ranging between 75%–76% and dominance of K2O (> 4.5%) over CaO (< 0.9%) suggest ashes have originated from siliceous rhyolitic melts, similar to the petrographic composition of tephra from the Toba volcano. The bulk trace element compositions of the same glass shards were comparable with those reported in the youngest Toba tephra reported elsewhere. Likewise, the LREE-dominated chondrite normalized REE profiles of tephra from the Mahanadi basin closely resemble the characteristic REE patterns in Toba ash from other parts of the Indian Ocean and thus confirmed the contribution of the youngest Toba super-eruption for this ash layers.
2024, 43(2): 120-129.
doi: 10.1007/s13131-023-2220-8
Abstract:
Mozambique’s continental margin in East Africa was formed during the break-off stage of the east and west Gondwana lands. Studying the geological structure and division of continent-ocean boundary (COB) in Mozambique’s continental margin is considered of great significance to rebuild Gondwana land and understand its movement mode. Along these lines, in this work, the initial Moho was fit using the known Moho depth from reflection seismic profiles, and a 3D multi-point constrained gravity inversion was carried out. Thus, high-accuracy Moho depth and crustal thickness in the study area were acquired. According to the crustal structure distribution based on the inversion results, the continental crust at the narrowest position of the Mozambique Channel was detected. According to the analysis of the crustal thickness, the Mozambique ridge is generally oceanic crust and the COB of the whole Mozambique continental margin is divided.
Mozambique’s continental margin in East Africa was formed during the break-off stage of the east and west Gondwana lands. Studying the geological structure and division of continent-ocean boundary (COB) in Mozambique’s continental margin is considered of great significance to rebuild Gondwana land and understand its movement mode. Along these lines, in this work, the initial Moho was fit using the known Moho depth from reflection seismic profiles, and a 3D multi-point constrained gravity inversion was carried out. Thus, high-accuracy Moho depth and crustal thickness in the study area were acquired. According to the crustal structure distribution based on the inversion results, the continental crust at the narrowest position of the Mozambique Channel was detected. According to the analysis of the crustal thickness, the Mozambique ridge is generally oceanic crust and the COB of the whole Mozambique continental margin is divided.
Yuzaoea gen. nov., a new biraphid diatom (Bacillariophyceae) genus and its phylogenetic significance
2024, 43(2): 130-136.
doi: 10.1007/s13131-023-2260-0
Abstract:
The flexed frustules in pennate diatoms are usually associated with monoraphid diatoms. Interestingly, we found a biraphid diatom species with flexed frustules in an offshore intertidal beach environment on Weizhou Island, Beihai City, Guangxi Zhuang Autonomous Region, China. Therefore, based on morphological characteristics, we described a new genus of diatoms Yuzaoea sinensis gen. et sp. nov. CH Li, HH Liu, YH Gao & CP Chen. The frustule of this genus is characterized by heterogeneous frustule with one concave valve and one convex valve, complete raphe on both valves, straight and moderately eccentric raphe, uniseriate striae and girdle bands with a single row of areolae. The most identifying feature of this genus was the flexed frustule, which is rare in biraphid diatoms and common in monoraphid diatoms. We compared the morphometric characteristics of genus Yuzaoea with genus Rhoikoneis and several genera within the family Rhoicospheniaceae, including Rhoicosphenia, Campylopyxis, and Cuneolus. Phylogenetic analyses based on SSU rRNA and rbcL showed that the genus Yuzaoea was the sister group to the clade of Rhoicosphenia with a high support value (bootstrap values = 100%), and the clade “Yuzaoea+Rhoicosphenia” was sister to the clade of monoraphid diatoms, in which the genera Achnanthidium, Planothidium and some Cocconeis with high support values (bootstrap = 100%). Morphologically, the genus Yuzaoea shares many morphological features with monoraphid diatoms like genera Achnanthidium and Planothidium and the members within the Rhoicospheniaceae. Therefore, based on a combined morphological studies and phylogenetic results we suggested that this branch may represented the evolution of one kind monoraphid diatoms, from biraphid diatoms (e.g. genus Yuzaoea), to incompleted biraphid diatoms (e.g. genera Rhoicosphenia, Campylopyxis), to monoraphid diatoms (e.g. genera Achnanthidium and Planothidium).
The flexed frustules in pennate diatoms are usually associated with monoraphid diatoms. Interestingly, we found a biraphid diatom species with flexed frustules in an offshore intertidal beach environment on Weizhou Island, Beihai City, Guangxi Zhuang Autonomous Region, China. Therefore, based on morphological characteristics, we described a new genus of diatoms Yuzaoea sinensis gen. et sp. nov. CH Li, HH Liu, YH Gao & CP Chen. The frustule of this genus is characterized by heterogeneous frustule with one concave valve and one convex valve, complete raphe on both valves, straight and moderately eccentric raphe, uniseriate striae and girdle bands with a single row of areolae. The most identifying feature of this genus was the flexed frustule, which is rare in biraphid diatoms and common in monoraphid diatoms. We compared the morphometric characteristics of genus Yuzaoea with genus Rhoikoneis and several genera within the family Rhoicospheniaceae, including Rhoicosphenia, Campylopyxis, and Cuneolus. Phylogenetic analyses based on SSU rRNA and rbcL showed that the genus Yuzaoea was the sister group to the clade of Rhoicosphenia with a high support value (bootstrap values = 100%), and the clade “Yuzaoea+Rhoicosphenia” was sister to the clade of monoraphid diatoms, in which the genera Achnanthidium, Planothidium and some Cocconeis with high support values (bootstrap = 100%). Morphologically, the genus Yuzaoea shares many morphological features with monoraphid diatoms like genera Achnanthidium and Planothidium and the members within the Rhoicospheniaceae. Therefore, based on a combined morphological studies and phylogenetic results we suggested that this branch may represented the evolution of one kind monoraphid diatoms, from biraphid diatoms (e.g. genus Yuzaoea), to incompleted biraphid diatoms (e.g. genera Rhoicosphenia, Campylopyxis), to monoraphid diatoms (e.g. genera Achnanthidium and Planothidium).
2024, 43(2): 137-150.
doi: 10.1007/s13131-023-2258-7
Abstract:
Caenogastropoda is a highly diverse group, containing ~60% of all existing gastropods. Species in this subclass predominantly inhabit marine environments and have a high ecological and economic value. Owing to the increase in relevant phylogenetic studies, our understanding of between species relatedness in Caenogastropoda has improved. However, the biodiversity, taxonomic status, and phylogenetic relationships of this group remain unclear. In the present study, we performed next-generation sequencing of four complete mitochondrial genomes from three families (Buccinidae, Columbellidae, and Cypraeidae) and the four mitogenomes were classical circular structures, with a length of 16 177 bp in Volutharpa ampullacea, 16 244 bp in Mitrella albuginosa, 16 926 bp in Mauritia arabica asiatica and 15 422 bp in Erronea errones. Base composition analysis indicated that whole sequences were biased toward A and T. Then compared them with 171 complete mitochondrial genomes of Caenogastropoda. The phylogenetic relationship of Caenogastropoda derived from Maximum Likelihood (ML) and Bayesian Inference (BI) trees constructed based on CDS sequences was consistent with the results of traditional morphological analysis, with all three families showing close relationships. This study supported Caenogastropoda at the molecular level as a separate clade of Mollusca. According to our divergence time estimations, Caenogastropoda was formed during the middle Triassic period (~247.2–237 Ma). Our novel mitochondrial genomes provide evidence for the speciation of Caenogastropoda in addition to elucidating the mitochondrial genomic evolution of this subclass.
Caenogastropoda is a highly diverse group, containing ~60% of all existing gastropods. Species in this subclass predominantly inhabit marine environments and have a high ecological and economic value. Owing to the increase in relevant phylogenetic studies, our understanding of between species relatedness in Caenogastropoda has improved. However, the biodiversity, taxonomic status, and phylogenetic relationships of this group remain unclear. In the present study, we performed next-generation sequencing of four complete mitochondrial genomes from three families (Buccinidae, Columbellidae, and Cypraeidae) and the four mitogenomes were classical circular structures, with a length of 16 177 bp in Volutharpa ampullacea, 16 244 bp in Mitrella albuginosa, 16 926 bp in Mauritia arabica asiatica and 15 422 bp in Erronea errones. Base composition analysis indicated that whole sequences were biased toward A and T. Then compared them with 171 complete mitochondrial genomes of Caenogastropoda. The phylogenetic relationship of Caenogastropoda derived from Maximum Likelihood (ML) and Bayesian Inference (BI) trees constructed based on CDS sequences was consistent with the results of traditional morphological analysis, with all three families showing close relationships. This study supported Caenogastropoda at the molecular level as a separate clade of Mollusca. According to our divergence time estimations, Caenogastropoda was formed during the middle Triassic period (~247.2–237 Ma). Our novel mitochondrial genomes provide evidence for the speciation of Caenogastropoda in addition to elucidating the mitochondrial genomic evolution of this subclass.
2024, 43(2): 151-155.
doi: 10.1007/s13131-023-2221-7
Abstract:
Acanthopagrus latus is an essential aquaculture species on the south coast of China. However, there is a lack of systematic breeding of A. latus, which considerably limits the sustainable development of A. latus. As a result, genetic improvements are urgently needed to breed new strains of A. latus with rapid growth and strong resistance to disease. During selective breeding, it is necessary to estimate the genetic parameters of the target trait, which in turn depends on an accurate disentangled pedigree for the selective population. Therefore, it is necessary to establish the parentage assignment technique for A. latus. In this study, 95 individuals selected from their parents and their 14 families were used as experimental material. SNPs were developed by genome re-sequencing, and highly polymorphic SNPs were screened on the basis of optimized filtering parameters. A total of 14 392 738 SNPs were discovered and 205 SNPs were selected for parentage assignment using the CERVUS software. In the model where the gender of the parents is known, the assignment success rate is 98.61% for the male parent, 97.22% for the female parent, and 95.83% for the parent pair. In the model where the gender of the parents is unknown, the assignment success rate is 100% for a single parent and 90.28% for the parent pair. The results of this study were expected to serve as a reference for the breeding of new varieties of A.latus.
Acanthopagrus latus is an essential aquaculture species on the south coast of China. However, there is a lack of systematic breeding of A. latus, which considerably limits the sustainable development of A. latus. As a result, genetic improvements are urgently needed to breed new strains of A. latus with rapid growth and strong resistance to disease. During selective breeding, it is necessary to estimate the genetic parameters of the target trait, which in turn depends on an accurate disentangled pedigree for the selective population. Therefore, it is necessary to establish the parentage assignment technique for A. latus. In this study, 95 individuals selected from their parents and their 14 families were used as experimental material. SNPs were developed by genome re-sequencing, and highly polymorphic SNPs were screened on the basis of optimized filtering parameters. A total of 14 392 738 SNPs were discovered and 205 SNPs were selected for parentage assignment using the CERVUS software. In the model where the gender of the parents is known, the assignment success rate is 98.61% for the male parent, 97.22% for the female parent, and 95.83% for the parent pair. In the model where the gender of the parents is unknown, the assignment success rate is 100% for a single parent and 90.28% for the parent pair. The results of this study were expected to serve as a reference for the breeding of new varieties of A.latus.
2024, 43(2): 156-160.
doi: 10.1007/s13131-023-2219-1
Abstract:
The resource of Fenneropenaeus chinensis has declined sharply due to excessive fishing intensity, ecological changes and diseases. In order to supplement the fishing yield and restore resources of F. chinensis, the relevant authorities have carried out the activities of stock enhancement and releasing. It can increase biomass and recover resources. However, compared with increasing biomass, there were still few reports on its effect on the recovery of resources. Resource recovery is a process related to whether the released individuals can form a reproductive population. Up to now, there has been a lack of evidence whether the released F. chinensis can complete the entire life history, and form reproduction population. In this study, gravid female shrimp after spawning migration were captured from coastal waters of Haiyang, Qingdao, and Yellow Sea. After identifying parentage relationships using simple sequence repeat (SSR) and mtDNA haplotype, it was finally confirmed that there were eight released individuals in the recapture samples. It was confirmed for the first time that at least part of the released F. chinensis can complete overwintering and reproductive migration, and maintain the migration habits as their wild counterparts. Therefore, we infered that the released shrimp can reproduce under natural conditions, these F. chinensis can form reproductive populations theoretically if without human intervention. These results indicated that enhancenment and release activities have a positive effect on resource recovery.
The resource of Fenneropenaeus chinensis has declined sharply due to excessive fishing intensity, ecological changes and diseases. In order to supplement the fishing yield and restore resources of F. chinensis, the relevant authorities have carried out the activities of stock enhancement and releasing. It can increase biomass and recover resources. However, compared with increasing biomass, there were still few reports on its effect on the recovery of resources. Resource recovery is a process related to whether the released individuals can form a reproductive population. Up to now, there has been a lack of evidence whether the released F. chinensis can complete the entire life history, and form reproduction population. In this study, gravid female shrimp after spawning migration were captured from coastal waters of Haiyang, Qingdao, and Yellow Sea. After identifying parentage relationships using simple sequence repeat (SSR) and mtDNA haplotype, it was finally confirmed that there were eight released individuals in the recapture samples. It was confirmed for the first time that at least part of the released F. chinensis can complete overwintering and reproductive migration, and maintain the migration habits as their wild counterparts. Therefore, we infered that the released shrimp can reproduce under natural conditions, these F. chinensis can form reproductive populations theoretically if without human intervention. These results indicated that enhancenment and release activities have a positive effect on resource recovery.
2024, 43(2): 161-167.
doi: 10.1007/s13131-023-2261-z
Abstract:
With the development of ultra-wide coverage technology, multibeam echo-sounder (MBES) system has put forward higher requirements for localization accuracy and computational efficiency of ray tracing method. The classical equivalent sound speed profile (ESSP) method replaces the measured sound velocity profile (SVP) with a simple constant gradient SVP, reducing the computational workload of beam positioning. However, in deep-sea environment, the depth measurement error of this method rapidly increases from the central beam to the edge beam. By analyzing the positioning error of the ESSP method at edge beam, it is discovered that the positioning error increases monotonically with the incident angle, and the relationship between them could be expressed by polynomial function. Therefore, an error correction algorithm based on polynomial fitting is obtained. The simulation experiment conducted on an inclined seafloor shows that the proposed algorithm exhibits comparable efficiency to the original ESSP method, while significantly improving bathymetry accuracy by nearly eight times in the edge beam.
With the development of ultra-wide coverage technology, multibeam echo-sounder (MBES) system has put forward higher requirements for localization accuracy and computational efficiency of ray tracing method. The classical equivalent sound speed profile (ESSP) method replaces the measured sound velocity profile (SVP) with a simple constant gradient SVP, reducing the computational workload of beam positioning. However, in deep-sea environment, the depth measurement error of this method rapidly increases from the central beam to the edge beam. By analyzing the positioning error of the ESSP method at edge beam, it is discovered that the positioning error increases monotonically with the incident angle, and the relationship between them could be expressed by polynomial function. Therefore, an error correction algorithm based on polynomial fitting is obtained. The simulation experiment conducted on an inclined seafloor shows that the proposed algorithm exhibits comparable efficiency to the original ESSP method, while significantly improving bathymetry accuracy by nearly eight times in the edge beam.
