A series of sub-parallel linear glacial scours are identified on the crest of the Baoshi Seamount in the Northwind Abyssal Plain by compiling new multibeam data acquired during the 9 th Chinese Arctic Research Expedit...A series of sub-parallel linear glacial scours are identified on the crest of the Baoshi Seamount in the Northwind Abyssal Plain by compiling new multibeam data acquired during the 9 th Chinese Arctic Research Expedition(CHINARE-Arc9)in 2018 and previously published data.The new data reveal scours that developed at water depths of 850–1030 m with an orientation of about 75°/255°.The maximum water depth occurs in the southernmost scour and is deeper than that from previous investigations,which showed a maximum scouring depth of about 900 m on the seamount.The topographic and geomorphological characteristics suggest that these scours resulted from erosion by the ice shelf extending from the Chukchi margin and/or Laurentide Ice Sheet that grounded on the crest of the seamount and moved in a NE–SW direction.Other possibilities of their genesis include armadas of large icebergs/multi-keel icebergs calved from the Chukchi Shelf or the Laurentide Ice Sheet.The new data provide new constraints for assessing the extent and volume of the ice sheet in the Chukchi area during glacial maxima.展开更多
The Chukchi Borderland is a relict continental block in the Arctic Ocean.Its origin and tectonic processes are of great significance for understanding the formation model of the Amerasia Basin and the configurations o...The Chukchi Borderland is a relict continental block in the Arctic Ocean.Its origin and tectonic processes are of great significance for understanding the formation model of the Amerasia Basin and the configurations of the Mesozoic Arctic regions.Due to the harsh environment and rare geological and geophysical data,the evolution of the Chukchi Borderland is still unclear(e.g.,Grantz et al.,1998,2011).We conducted two rock dredges and a multibeam full coverage survey of 830 km2 in the Northwind Abyssal Plain of the Chukchi Borderland during the Chinese ninth Arctic scientific expedition in 2018.This is the first rock dredge survey of China in the polar regions with floating ice,and is just after the HLY0905 dredge at the Northwind Abyssal Plain in 2009(Mayer and Armstrong,2011).The retrieved samples will provide new information for understanding the origin and tectonic evolution of the Chukchi Borderland.展开更多
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 s...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.展开更多
On September 5,2019,a moderate earthquake of Mw5.4 unexpectedly occurred in the apparently quiescent central basin of the South China Sea.We immediately carried out a seismicity monitoring experiment around the epicen...On September 5,2019,a moderate earthquake of Mw5.4 unexpectedly occurred in the apparently quiescent central basin of the South China Sea.We immediately carried out a seismicity monitoring experiment around the epicenter by using broadband ocean bottom seismometers(OBS)for the following three scientific targets.The first is knowing the earthquake seismogenic mechanism,fault structure and further development.The second is finding the role of the residual spreading ridge playing in earthquake processes and further revealing the deep structures of the ridge directional turning area.The third is confirming the existence and significance of the so called“Zhongnan fault”.This paper reports the preliminary results of the first phase experiment.Five OBSs were deployed for seismicity monitoring with a duration of 288 days,but only three were recovered.Micro-earthquakes were firstly detected by an automatic seismic phase picking algorithm and then were verified by analyzing their seismic phases and time-frequency characteristics in detail.A total of 21,68 and 89 microearthquakes were picked out from the three OBSs respectively within the distance of 30 km.The dominant frequency of these micro-earthquakes is 12-15 Hz,indicating tectonic fracturing.During the first two months after the mainshock the seismicity was relatively stronger,and micro-earthquakes were still occurring occasionally till the end of observation,indicating the epicenter area is active.We used Match&Locate method to locate 57 micro-earthquakes preliminarily.Their spatial distribution shows that the seismicity is developed mainly along the NE direction roughly parallel to the residual ridge with depth variations between 10-20 km.展开更多
基金The National Natural Science Foundation of China under contract No.41976079the Chinese Polar Environment Comprehensive Investigation and Assessment Programmes under contract No.CHINARE-03-03。
文摘A series of sub-parallel linear glacial scours are identified on the crest of the Baoshi Seamount in the Northwind Abyssal Plain by compiling new multibeam data acquired during the 9 th Chinese Arctic Research Expedition(CHINARE-Arc9)in 2018 and previously published data.The new data reveal scours that developed at water depths of 850–1030 m with an orientation of about 75°/255°.The maximum water depth occurs in the southernmost scour and is deeper than that from previous investigations,which showed a maximum scouring depth of about 900 m on the seamount.The topographic and geomorphological characteristics suggest that these scours resulted from erosion by the ice shelf extending from the Chukchi margin and/or Laurentide Ice Sheet that grounded on the crest of the seamount and moved in a NE–SW direction.Other possibilities of their genesis include armadas of large icebergs/multi-keel icebergs calved from the Chukchi Shelf or the Laurentide Ice Sheet.The new data provide new constraints for assessing the extent and volume of the ice sheet in the Chukchi area during glacial maxima.
基金The National Natural Science Foundation of China under contract No.41576065the Chinese Polar Environment Comprehensive Investigation and Assessment Programmes under contract Nos CHINARE 03-03 and CHINARE 04-03
文摘The Chukchi Borderland is a relict continental block in the Arctic Ocean.Its origin and tectonic processes are of great significance for understanding the formation model of the Amerasia Basin and the configurations of the Mesozoic Arctic regions.Due to the harsh environment and rare geological and geophysical data,the evolution of the Chukchi Borderland is still unclear(e.g.,Grantz et al.,1998,2011).We conducted two rock dredges and a multibeam full coverage survey of 830 km2 in the Northwind Abyssal Plain of the Chukchi Borderland during the Chinese ninth Arctic scientific expedition in 2018.This is the first rock dredge survey of China in the polar regions with floating ice,and is just after the HLY0905 dredge at the Northwind Abyssal Plain in 2009(Mayer and Armstrong,2011).The retrieved samples will provide new information for understanding the origin and tectonic evolution of the Chukchi Borderland.
基金supported by the Impact and Response of Antarctic Seas to Climate Change Project (IRASCC01-03-01)Hainan Naturtal Science Foundation Inovative Research Team Project (421CXTD441)the National Natural Science Foundation of China (Nos. 42176067, 41576069, 42176055, 41776189 and 41906197)
文摘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.
基金jointly supported by the National Natural Science Foundation of China(Nos.42076047,41890811)。
文摘On September 5,2019,a moderate earthquake of Mw5.4 unexpectedly occurred in the apparently quiescent central basin of the South China Sea.We immediately carried out a seismicity monitoring experiment around the epicenter by using broadband ocean bottom seismometers(OBS)for the following three scientific targets.The first is knowing the earthquake seismogenic mechanism,fault structure and further development.The second is finding the role of the residual spreading ridge playing in earthquake processes and further revealing the deep structures of the ridge directional turning area.The third is confirming the existence and significance of the so called“Zhongnan fault”.This paper reports the preliminary results of the first phase experiment.Five OBSs were deployed for seismicity monitoring with a duration of 288 days,but only three were recovered.Micro-earthquakes were firstly detected by an automatic seismic phase picking algorithm and then were verified by analyzing their seismic phases and time-frequency characteristics in detail.A total of 21,68 and 89 microearthquakes were picked out from the three OBSs respectively within the distance of 30 km.The dominant frequency of these micro-earthquakes is 12-15 Hz,indicating tectonic fracturing.During the first two months after the mainshock the seismicity was relatively stronger,and micro-earthquakes were still occurring occasionally till the end of observation,indicating the epicenter area is active.We used Match&Locate method to locate 57 micro-earthquakes preliminarily.Their spatial distribution shows that the seismicity is developed mainly along the NE direction roughly parallel to the residual ridge with depth variations between 10-20 km.