Several significant events of a geological nature occurred approximately 800 ka before the present: (1) Australasian tektite fall (AA), (2) Brunhes-Matuyama geomagnetic reversal (BMR), (3) mid-Pleistocene changes in i...Several significant events of a geological nature occurred approximately 800 ka before the present: (1) Australasian tektite fall (AA), (2) Brunhes-Matuyama geomagnetic reversal (BMR), (3) mid-Pleistocene changes in ice age cycles. Add to these the undated fault system (4) in the South-West (SW) of the South China Sea (SCS). Here we offer a unified cause for all four of these in (5), an impact in the SCS of a large, massive cosmic object, likely a comet, obliquely coming from the SW at an extremely shallow angle, striking the Sunda shelf yet unexploded with the shock of its compressed air bow wave, and causing the continual shelf and slope to collapse, resulting in the fault system (4), then traveling almost tangentially to the surface, exploding at impact with the sea surface, ejecting the tektites (1), creating the formation underlying the later atolls of Spratlies Archipelago (6), Nansha Islands in Chinese, & causing the BMR (2). An explanation of event (3) was Richard Muller’s hypothesis of planet Earth passing through an interplanetary dust cloud periodically due to ecliptic precession. Here we hypothesize this cloud actually is a belt of Australasian tektites ejected into space at super-orbital velocities that Earth encounters about every 100 ka.展开更多
Climate change impacts bird migration phenology,causing changes in departure and arrival dates,leading to potential mismatches between migration and other key seasonal constraints.While the impacts of climate change o...Climate change impacts bird migration phenology,causing changes in departure and arrival dates,leading to potential mismatches between migration and other key seasonal constraints.While the impacts of climate change on arrival at breeding grounds have been relatively well documented,little is known about the impacts of climate change on post-breeding migration,especially at stopover sites.Here we use long-term(11 years)banding data(11,118 captures)from 7 species at Mai Po Marshes Nature Reserve in Hong Kong,a key stopover site for migratory birds along the East Asian–Australasian Flyway,to describe long-term changes in migration phenology and to compare observed changes to annual weather variation.We also examine changes in wing length over a longer time period(1985–2020)as wing length often correlates positively with migration distance.We found that observed changes in migratory phenology vary by species;three species had later estimated arrival(by 1.8 days per year),peak(by 2.6 days per year)or departure(by 2.5 days per year),one showed an earlier peak date(by 1.8days per year)and two showed longer duration of passage(2.7 days longer and 3.2 days longer per year).Three species exhibited no long-term change in migration phenology.For two of the four species with shifting phenology,temperature was an important predictor of changing peak date,departure dates and duration of passage.Wing length was shorter in three species and longer in two species,but these changes did not correlate with observed phenological changes.The complex changes observed here are indicative of the challenges concerning the detection of climate change in migratory stopover sites.Continued monitoring and a better understanding of the dynamics of all sites in the migratory pathway will aid conservation of these species under global change.展开更多
Background:Avian migrants moving between common breeding and wintering areas may adopt different migration routes,and consequently affect timing.However,this pattern has rarely been investigated,especially in waterbir...Background:Avian migrants moving between common breeding and wintering areas may adopt different migration routes,and consequently affect timing.However,this pattern has rarely been investigated,especially in waterbirds.Moreover,autumn migration patterns of the Common Shelduck(Tadorna tadorna) have never been studied.Methods:We used GPS transmitters to track,for the first time,the autumn migration of the Common Shelduck in East Asia(n = 14).Results:The Common Shelduck undertook a broadly northwest–southeast autumn migration,taking a mean of 91.7 ± 38.7(SD) days to cover a mean distance of 1712.9 ± 450.5 km at a speed of 89.4 ± 226.5 km/day.The birds used 2.5 ± 1.8 stopover sites,and the total stopover duration was 81.9 ± 38.7 days.There were considerable betweenindividual variations in the onset(24 August to 28 September) and completion(29 September to 11 January) of migration,distance(1070.2–2396.4 km),speed(14.7-734.0 km/day),the index of straightness(0.6-1.0),duration(1.5-151.8 days),stopover times(0-5) and total stopover durations(0-148.1).More direct migration routes were associated with fewer and shorter stopovers(p = 0.003 in both cases).Post-breeding and wintering site habitat use was similar between individuals,whereas stopover site habitat use varied considerably within and between individuals.Conclusions:Our study showed remarkable variability in Shelduck migration patterns,which was likely associated with refuelling patterns en route.To understand fully the migration diversity and flexibility of habitat-use,we need to track more birds to increase representativeness,using accelerometer-integrated transmitters to investigate behaviours in different habitats.展开更多
A sedimentary profile exposed in soil quarries a few kilometers north of Noen Sa-nga district,Chaiyaphum province,NE Thailand,reveals a Quaternary geological history.The lower part of the soil profile is a gravel depo...A sedimentary profile exposed in soil quarries a few kilometers north of Noen Sa-nga district,Chaiyaphum province,NE Thailand,reveals a Quaternary geological history.The lower part of the soil profile is a gravel deposit characterized by sub-angular to well-rounded pebbles representing an abandoned river sedimentary deposit.The gravel bed in some places is coated by iron oxide as a thin layer of ferricrete at the uppermost part.The upper part of the soil profile is a bright reddish brown structureless sand deposit with fining upward sedimentary structure at the basal portion,the Yasothon soil series.A piece of tektite was discovered at the contact boundary between the two sedimentary units.It is characterized by an irregular shape with a smooth concaved surface regarding as an external mold of a piece of well-rounded pebble.This piece of tektite indicates that a solidified tektite had fallen from high sky then was remelted into a plastic form prior to reach and partly cover a piece of well-rounded pebble.These evidences suggest that there was a meteoritic or cometary impact on our earth surface somewhere in the region then catapulted numbers of melted silica ejecta with vast volume of dust into the sky.The melted silica ejecta were solidified into splash-form tektites with various shapes while they were in the high sky.After that the tektites had fallen down and remelted into a plastic form prior to reach the ground surface and then solidified as a tektite deposit followed by larger-sized sediments and angular quartz fragments forming a fining upward sedimentary structure.The finer sediments were gradually settled down forming a bright reddish brown structureless sand deposit,the Yasothon soil series.This meteoritic impact event occurred at about 0.77 Ma ago as the evidence of the previous tektite radiometric dating.展开更多
Background: Departure decisions and behaviors of migratory birds at stopover sites are expected to maximize fit?ness by trade?offs among avoiding predators, optimizing refueling(energy) capacity, and matching other li...Background: Departure decisions and behaviors of migratory birds at stopover sites are expected to maximize fit?ness by trade?offs among avoiding predators, optimizing refueling(energy) capacity, and matching other life?history events. We predict that species with different body sizes and migratory destinations will exhibit different behaviors when departing from the same stopover site. We also predict that with strong time constraint at the final pre?breed?ing stopover site, departure decisions may be less sensitive to exogenous factors, such as wind condition, compared to other stopover or nonbreeding sites.Methods: We recorded migratory departures of four shorebird species, i.e. Eurasian Curlew(Numenius arquata), Bar?tailed Godwit(Limosa lapponica), Great Knot(Calidris tenuirostris), and Grey Plover(Pluvialis squatarola), at Yaluji?ang Estuary Wetlands in China, a final pre?breeding stopover site in the northern Yellow Sea, from 2011 to 2014. We compared flock sizes, departure time and departure directions between species, and investigated the effects of tide and weather conditions(rain and ground wind speed and direction) on the departure decision of shorebirds.Results: We found that larger species departed in smaller flocks and were more variable in daily departure time. Departure trajectory of all four species appeared to be influenced by coastal topography. With the east–west coast?line and intertidal mudflat on the south, birds exhibited westward or eastward deflection from the shortest migra?tory routes. Bar?tailed Godwit was the only species that deviated to the southeast and did not climb over the land. Birds avoided departure during precipitation, while their departure was not related to ground wind benefit or tidal condition.Conclusions: Body size among species, which influences their vulnerability to predators, might be important in shaping shorebird departure strategies. Diverse departure directions could be the result of different wind use tac?tics in climbing stage. Narrow optimal time window of breeding might lead to reduced flexibility in departure date at a final pre?breeding site. Both endogenous and exogenous are important in shaping departure behaviors and decisions.展开更多
Six tektites from Guilin of Guangxi, Hainan, and Guangdong were analyzed for the abundances of major elements and 27 trace elements. All samples are splash-form tektites and have SiO2 contents ranging from 73.1wt% to ...Six tektites from Guilin of Guangxi, Hainan, and Guangdong were analyzed for the abundances of major elements and 27 trace elements. All samples are splash-form tektites and have SiO2 contents ranging from 73.1wt% to 76.0wt% (74.6wt% on average). The chemical compositions, except Cr and Ni, of tektites from different areas, are similar. Guangdong tektite shows enrichments of Ni and Cr contents by a factor of 3, and has slightly higher MgO and FeO than Hainan and Guilin tektites. It indicates that the tektites were formed by mixing several target rocks. The major and trace element concentrations of southern China tektites closely resemble previously reported data for average splash-form and Muong Nong-type indochinites, indicating that they have the same source. (La/Lu)CI (7.99), Zr/Hf (35.45 on average), Ba/Rb (3.59 on average), and the rare earth element (REE) contents of tektites are similar to those of typical post Archean upper crustal rocks. This study suggests that the best fit for the target source of southern China tektites could be a combination of 41% shale, 2% sandstone, 20% greywacke, and 37% quartzite.展开更多
Two sediment cores, MD06-3050 and MD06-3047, were analyzed to study the Quaternary calcareous nannofossil and microtektite records. We dated bioevents and the microtektite impact event by calibrating with oxygen isoto...Two sediment cores, MD06-3050 and MD06-3047, were analyzed to study the Quaternary calcareous nannofossil and microtektite records. We dated bioevents and the microtektite impact event by calibrating with oxygen isotope stratigraphy. Seven calcareous nannofossil bioevents were identified over the past 2.36 Ma including the last appearance of data for Discoaster brouweri, Calcidiscus macintyrei, large Gephyrocapsa and Pseudoemiliania lacunosa, the first appearance of data for large Gephyrocapsa and Emiliania huxleyi, and the abrupt increase in the abundance of Gephyrocapsa caribbeanica. In addition, we fortunately observed that Australasian microtektites were distributed in core MD06-3050 from 1340 to 1374 cm.展开更多
文摘Several significant events of a geological nature occurred approximately 800 ka before the present: (1) Australasian tektite fall (AA), (2) Brunhes-Matuyama geomagnetic reversal (BMR), (3) mid-Pleistocene changes in ice age cycles. Add to these the undated fault system (4) in the South-West (SW) of the South China Sea (SCS). Here we offer a unified cause for all four of these in (5), an impact in the SCS of a large, massive cosmic object, likely a comet, obliquely coming from the SW at an extremely shallow angle, striking the Sunda shelf yet unexploded with the shock of its compressed air bow wave, and causing the continual shelf and slope to collapse, resulting in the fault system (4), then traveling almost tangentially to the surface, exploding at impact with the sea surface, ejecting the tektites (1), creating the formation underlying the later atolls of Spratlies Archipelago (6), Nansha Islands in Chinese, & causing the BMR (2). An explanation of event (3) was Richard Muller’s hypothesis of planet Earth passing through an interplanetary dust cloud periodically due to ecliptic precession. Here we hypothesize this cloud actually is a belt of Australasian tektites ejected into space at super-orbital velocities that Earth encounters about every 100 ka.
基金Funding was provided by an RAE Improvement Grant to(TCB)from the Faculty of Science at The University of Hong Kong。
文摘Climate change impacts bird migration phenology,causing changes in departure and arrival dates,leading to potential mismatches between migration and other key seasonal constraints.While the impacts of climate change on arrival at breeding grounds have been relatively well documented,little is known about the impacts of climate change on post-breeding migration,especially at stopover sites.Here we use long-term(11 years)banding data(11,118 captures)from 7 species at Mai Po Marshes Nature Reserve in Hong Kong,a key stopover site for migratory birds along the East Asian–Australasian Flyway,to describe long-term changes in migration phenology and to compare observed changes to annual weather variation.We also examine changes in wing length over a longer time period(1985–2020)as wing length often correlates positively with migration distance.We found that observed changes in migratory phenology vary by species;three species had later estimated arrival(by 1.8 days per year),peak(by 2.6 days per year)or departure(by 2.5 days per year),one showed an earlier peak date(by 1.8days per year)and two showed longer duration of passage(2.7 days longer and 3.2 days longer per year).Three species exhibited no long-term change in migration phenology.For two of the four species with shifting phenology,temperature was an important predictor of changing peak date,departure dates and duration of passage.Wing length was shorter in three species and longer in two species,but these changes did not correlate with observed phenological changes.The complex changes observed here are indicative of the challenges concerning the detection of climate change in migratory stopover sites.Continued monitoring and a better understanding of the dynamics of all sites in the migratory pathway will aid conservation of these species under global change.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFC0505800)the National Natural Science Foundation of China(Grant Nos.31661143027,31670424,31500315)China Biodiversity Observation Networks(Sino BON)
文摘Background:Avian migrants moving between common breeding and wintering areas may adopt different migration routes,and consequently affect timing.However,this pattern has rarely been investigated,especially in waterbirds.Moreover,autumn migration patterns of the Common Shelduck(Tadorna tadorna) have never been studied.Methods:We used GPS transmitters to track,for the first time,the autumn migration of the Common Shelduck in East Asia(n = 14).Results:The Common Shelduck undertook a broadly northwest–southeast autumn migration,taking a mean of 91.7 ± 38.7(SD) days to cover a mean distance of 1712.9 ± 450.5 km at a speed of 89.4 ± 226.5 km/day.The birds used 2.5 ± 1.8 stopover sites,and the total stopover duration was 81.9 ± 38.7 days.There were considerable betweenindividual variations in the onset(24 August to 28 September) and completion(29 September to 11 January) of migration,distance(1070.2–2396.4 km),speed(14.7-734.0 km/day),the index of straightness(0.6-1.0),duration(1.5-151.8 days),stopover times(0-5) and total stopover durations(0-148.1).More direct migration routes were associated with fewer and shorter stopovers(p = 0.003 in both cases).Post-breeding and wintering site habitat use was similar between individuals,whereas stopover site habitat use varied considerably within and between individuals.Conclusions:Our study showed remarkable variability in Shelduck migration patterns,which was likely associated with refuelling patterns en route.To understand fully the migration diversity and flexibility of habitat-use,we need to track more birds to increase representativeness,using accelerometer-integrated transmitters to investigate behaviours in different habitats.
基金the Northeastern Research Institute of Petrified Wood and Mineral Resources,Nakhon Ratchasima Rajabhat University,for financial and logistical supports throughout the research project
文摘A sedimentary profile exposed in soil quarries a few kilometers north of Noen Sa-nga district,Chaiyaphum province,NE Thailand,reveals a Quaternary geological history.The lower part of the soil profile is a gravel deposit characterized by sub-angular to well-rounded pebbles representing an abandoned river sedimentary deposit.The gravel bed in some places is coated by iron oxide as a thin layer of ferricrete at the uppermost part.The upper part of the soil profile is a bright reddish brown structureless sand deposit with fining upward sedimentary structure at the basal portion,the Yasothon soil series.A piece of tektite was discovered at the contact boundary between the two sedimentary units.It is characterized by an irregular shape with a smooth concaved surface regarding as an external mold of a piece of well-rounded pebble.This piece of tektite indicates that a solidified tektite had fallen from high sky then was remelted into a plastic form prior to reach and partly cover a piece of well-rounded pebble.These evidences suggest that there was a meteoritic or cometary impact on our earth surface somewhere in the region then catapulted numbers of melted silica ejecta with vast volume of dust into the sky.The melted silica ejecta were solidified into splash-form tektites with various shapes while they were in the high sky.After that the tektites had fallen down and remelted into a plastic form prior to reach the ground surface and then solidified as a tektite deposit followed by larger-sized sediments and angular quartz fragments forming a fining upward sedimentary structure.The finer sediments were gradually settled down forming a bright reddish brown structureless sand deposit,the Yasothon soil series.This meteoritic impact event occurred at about 0.77 Ma ago as the evidence of the previous tektite radiometric dating.
基金financially supported by the National Natural Science Foundation of China(31071939,31572280,and 31772467)
文摘Background: Departure decisions and behaviors of migratory birds at stopover sites are expected to maximize fit?ness by trade?offs among avoiding predators, optimizing refueling(energy) capacity, and matching other life?history events. We predict that species with different body sizes and migratory destinations will exhibit different behaviors when departing from the same stopover site. We also predict that with strong time constraint at the final pre?breed?ing stopover site, departure decisions may be less sensitive to exogenous factors, such as wind condition, compared to other stopover or nonbreeding sites.Methods: We recorded migratory departures of four shorebird species, i.e. Eurasian Curlew(Numenius arquata), Bar?tailed Godwit(Limosa lapponica), Great Knot(Calidris tenuirostris), and Grey Plover(Pluvialis squatarola), at Yaluji?ang Estuary Wetlands in China, a final pre?breeding stopover site in the northern Yellow Sea, from 2011 to 2014. We compared flock sizes, departure time and departure directions between species, and investigated the effects of tide and weather conditions(rain and ground wind speed and direction) on the departure decision of shorebirds.Results: We found that larger species departed in smaller flocks and were more variable in daily departure time. Departure trajectory of all four species appeared to be influenced by coastal topography. With the east–west coast?line and intertidal mudflat on the south, birds exhibited westward or eastward deflection from the shortest migra?tory routes. Bar?tailed Godwit was the only species that deviated to the southeast and did not climb over the land. Birds avoided departure during precipitation, while their departure was not related to ground wind benefit or tidal condition.Conclusions: Body size among species, which influences their vulnerability to predators, might be important in shaping shorebird departure strategies. Diverse departure directions could be the result of different wind use tac?tics in climbing stage. Narrow optimal time window of breeding might lead to reduced flexibility in departure date at a final pre?breeding site. Both endogenous and exogenous are important in shaping departure behaviors and decisions.
基金supported by National Natural Science Foundation of China (Grant Nos. 40773046 and 10621303)Minor Planet Foundation of China
文摘Six tektites from Guilin of Guangxi, Hainan, and Guangdong were analyzed for the abundances of major elements and 27 trace elements. All samples are splash-form tektites and have SiO2 contents ranging from 73.1wt% to 76.0wt% (74.6wt% on average). The chemical compositions, except Cr and Ni, of tektites from different areas, are similar. Guangdong tektite shows enrichments of Ni and Cr contents by a factor of 3, and has slightly higher MgO and FeO than Hainan and Guilin tektites. It indicates that the tektites were formed by mixing several target rocks. The major and trace element concentrations of southern China tektites closely resemble previously reported data for average splash-form and Muong Nong-type indochinites, indicating that they have the same source. (La/Lu)CI (7.99), Zr/Hf (35.45 on average), Ba/Rb (3.59 on average), and the rare earth element (REE) contents of tektites are similar to those of typical post Archean upper crustal rocks. This study suggests that the best fit for the target source of southern China tektites could be a combination of 41% shale, 2% sandstone, 20% greywacke, and 37% quartzite.
基金supported by the Pilot Project of the National Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-221)the National Natural Science Foundation of China (40906030,40976026and40906038)the National Basic Research Program of China (2007CB815903)
文摘Two sediment cores, MD06-3050 and MD06-3047, were analyzed to study the Quaternary calcareous nannofossil and microtektite records. We dated bioevents and the microtektite impact event by calibrating with oxygen isotope stratigraphy. Seven calcareous nannofossil bioevents were identified over the past 2.36 Ma including the last appearance of data for Discoaster brouweri, Calcidiscus macintyrei, large Gephyrocapsa and Pseudoemiliania lacunosa, the first appearance of data for large Gephyrocapsa and Emiliania huxleyi, and the abrupt increase in the abundance of Gephyrocapsa caribbeanica. In addition, we fortunately observed that Australasian microtektites were distributed in core MD06-3050 from 1340 to 1374 cm.
