Zhao Quanhong

The Krithe problem: A case history of the distribution of Krithe and Parakrithe (Crustacea, Ostracoda) in the South China Sea

Abstract The distribution of 12 species of Krithe and 4 species of Parakrithe through the depth range of 150–4000 m and 5 depth stratified water masses in the South China Sea reveals that there is no correlation between size and shape of the anterior vestibulum and levels of dissolved oxygen, nor between the length of specimens and water depth. Given this evidence from elsewhere, it is recommended that the Peypouquet hypothesis, which argues for these relationships, should be re-evaluated and not used as a palaeoceanographical tool. It is suggested that the relative abundance of Krithe, as a percentage of the total ostracod fauna, may be an important factor in reconstructing palaeodepth. In the South China Sea, despite its somewhat restricted nature and endemically low oxygen levels, the Krithidae are shown to be the dominant deep-sea Ostracoda.

Recent podocopid Ostracoda of the Sedili River and Jason Bay, southeastern Malay Peninsula

The recent podocopid Ostracoda of the Sedili River, its estuary and the open shelf of Jason Bay, off the southeast coast of the Malay Peninsula, have been studied quantitatively. The distribution of live and dead assemblages is recorded. A total of 101 species were recorded in the study. Of these, 50 were recorded live in the area. In the freshwater system of the Sedili River, only two species were recorded live, in the brackish water of the Sedili Estuary only 4 live species were recorded while 48 live species were recovered from the open shelf. The dead assemblage exhibits a much higher diversity yet lower dominance than the live assemblage and constitutes a total of 98 species from the 3 biotopes. The dead representatives of species which also occur live are more widely distributed than their live counterparts due to postmortem transportation. In this study one new genus is erected, Malaycythereis, n. gen., and the following new species and subspecies are erected: Malaycythereis trachodes, Caudites asiaticus, C. scopulicolusjasonensis, Cytherella incohatus, Hemicytheridea wangi, Keijella gonia, Loxoconcha malayensis, L. triconicula, Neocytheretta murilineata, Paracytheroma ventrosinuosa, Semicytherura contraria, Leptocythere pulchra, and Xestoleberis malaysiana.

Neogene oxygen isotopic stratigraphy, ODP Site 1148, northern South China Sea

A detailed stable isotopic study based on benthic foraminifera from 1165 samples of ODP Site 1148 (18° 50.17.3’N, 116° 33.93’E, water depth 3308.3 m), northern South China Sea, provides an excellent oxygen isotopic record with an average resolution of 30 ka. It contains the most continuous δ18O data with highest resolution for the whole Neogene sequence in the world. The δ18O curve shows a step-like increasing upwards and records 5 increases, 3 decreases and 2 stable stages during the Neogene, reflecting the general trend of global cooling. Among these events the δ18O decrease at 17.2–14.5 Ma, and two δ18O increases at 14.5-13.6 and 3.0-2.4 Ma are most marked and globally comparable. The intervals at 13.6-10.2 and 6.0-3.0 Ma with the lowest-amplitude and least fluctuation in δ18O represent the most stable bottom water periods for the South China Sea.

A record of Miocene carbon excursions in the South China Sea

High-resolution δ13C records are presented for the Miocene benthic foraminifersCibicidoides wuellerstorfi andC. kullenbergi (24-5 Ma) and the planktonic foraminiferGlobigerinoides sacculifer (18-5 Ma) from ODP Site 1148A (18° 50.17’N, 116° 33.93’E, water depth 3308.3 m), northern South China Sea. The general pattern of parallel benthic and planktonic δ13C shows a decrease trend of δ13C values from the early-middle Miocene to the middle-late Miocene. Two distinct δ13C positive excursions at 23.1-22.2 and 17.3-13.6 Ma, and two negative excursions at 10.2-9.4 and 6.9-6.2 Ma have been recognized. All these events are cosmopolitan, providing the good data for the stratigraphic correlation of the South China Sea with the global oceans as well as for studying the changes of the global carbon reservoir and its corresponding climate.

Oxygen isotope stratigraphy and events in the northern South China Sea during the last 6 million years

Based on the stable isotopic analysis of more than 1000 samples of planktonic and benthic foraminifers from ODP Site 1148 in the northern South China Sea (SCS), the oxygen isotope stratigraphy has been applied to the last 3 million years for the first time in the SCS. Furthermore, the paleoceanographic changes in the northern SCS during the last 6 million years have been unraveled. The benthic foraminiferal δ18O record shows that before δ3.1 Ma the SCS was much more influenced by the warm intermediate water of the Pacific. The remarkable decrease in the deepwater temperature of the SCS during the period of 3.1-2.5 Ma demonstrates the formation of the Northern Hemisphere ice-sheet. However, the several sea surface temperature (SST) reductions during the early and middle Pliocene, reflected by the planktonic foraminiferal δ18O, might be related to the ice-sheet growth in the Antarctic region. Only those stepwise and irreversible SST reductions during the period of δ2.2-0.9 Ma could be related to the formation and growth of the Northern Hemisphere ice-sheet.Based on the stable isotopic analysis of more than 1000 samples of planktonic and benthic foraminifers from ODP Site 1148 in the northern South China Sea (SCS), the oxygen isotope stratigraphy has been applied to the last 3 million years for the first time in the SCS. Furthermore, the paleoceanographic changes in the northern SCS during the last 6 million years have been unraveled. The benthic foraminiferal δ 18 O record shows that before ~3.1 Ma the SCS was much more influenced by the warm intermediate water of the Pacific. The remarkable decrease in the deepwater temperature of the SCS during the period of 3.1—2.5 Ma demonstrates the formation of the Northern Hemisphere ice-sheet. However, the several sea surface temperature (SST) reductions during the early and middle Pliocene, reflected by the planktonic foraminiferal δ 18 O, might be related to the ice-sheet growth in the Antarctic region. Only those stepwise and irreversible SST reductions during the period of ~2.2—0.9 Ma could be related to the formation and growth of the Northern Hemisphere ice-sheet.

Age estimation of the mid-Pleistocene microtektite event in the South China Sea: A case showing the complexity of the sea-land correlation

The present study confirms the stratigraphical position of microtektite layer being clearly located below the Brunhes/Matuyama (BIM) boundary. Based on the sedimentation rate derived from the stable isotopic and magnetic data of ODP Site 772A, cores 17957 and 17959 in the South China Sea, the age of the mid-Pleistocene impact event was estimated at 1–12 ka earlier than the Brunhes-Matuyama polarity reversal. However, the microtektites were found above the measured BIM boundary in the loess profile due to the downward deviation of the measured B/M boundary from its true position[1]. This demonstrates the complexity of paleo-magnetic records in the loess profiles which, in turn, causes the confusion in the sea-land stratigraphic correlation.

A revision of Brady’s 1869 study of the Ostracoda of Hong Kong

This paper is a revision of Brady’s 1869 study of the Ostracoda of Hong Kong in ‘Les Fonds de la Mer’. In this he described the following nine new species: Cyrherella cingulata, Bairdia elegans, Bythocythere orientalis, Loxoconcha sinensis, L. hastata, Cytheridea impressa, Cythere cymba, C. euplectella and C. salebrosa. A detailed reappraisal of Brady’s original material which is deposited in the Hancock Museum, Newcastle-upon-Tyne, UK, and the Centre d’Etudes et de Recherches Scientifiques, Biarritz, France has revealed that the specimens of L. hastata are apparently lost. Holotypes and lectotypes have been designated by the authors for the other eight species. Those species which were subsequently recorded by Brady (1880) in the Challenger Report, such as C. cingulata, B. orientalis, L. sinensis and C. euplectella are demonstrated not to be conspecific with their original types first described in 1869. The following 10 species, Bythoceratina virgatella Hu, 1983 and B. cassidoidea Zhao, 1985; Cyprideis yehi Hu & Yeh, 1978, Sinocytheridea sinensis Hou. 1978, S. latiovata Hou & Chen, 1982, 5. lotjga Hou & Chen, 1982 and Eucytheridea sinobesani Hu, 1984: Cythereis subconvexa Kajiyama, 1913 and Aurila miii Ishizaki, 1968: Cythereis assimilis Kajiyama. 1913 are placed by the authors in the synonymies of Brady’s B. orientalis, C. impressa, C. cymba and C. salebrosa respectively.

Late Quaternary eolian records in the northwest Pacific with glacial cycles: a comparison

Two deep-sea cores in the northwest Pacific have been analysed for sedimentology, mineralogy and environmental magnetism. The results show that after eliminating the interference from volcanism, several proxies such as quartz content, mass susceptibility and anhysteretic magnetic remanence can be used to indicate the eolian deposit from East Asia, and provide information on paleo-atmospheric circulation. A comparison of eolian record in Cure RC10-175 with its oxygen isotopic curve has revealed that the peaks of eolian accumulation occurred at the climatic “optimum” of the Holocene and the last interglaciation, showing the fairly complex nonlinear relationship between continental/pelagic eolian records and the global glacial cycles as well as within the climatic and environmental system.Two deep-sea cores in the northwest Pacific have been analysed for sedimentology, mineralogy and environmental magnetism. The results show that after eliminating the interference from volcanism, several proxies such as quartz content, mass susceptibility and anhysteretic magnetic remanence can be used to indicate the eolian deposit from East Asia, and provide information on paleo-atmospheric circulation. A comparison of eolian record in Cure RC10-175 with its oxygen isotopic curve has revealed that the peaks of eolian accumulation occurred at the climatic “optimum” of the Holocene and the last interglaciation, showing the fairly complex nonlinear relationship between continental/pelagic eolian records and the global glacial cycles as well as within the climatic and environmental system.

TSPIXE analysis of Mg/Ca ratios in ostracode shells

The μm-PIXE setup of Fudan University has been used to study the trace elements of ostracode shells. Program TSPIXE was used to calculate their trace element concentrations.Stenocypris derupta Vavra, Dolerocypria mukaishimensis okubo andTanella opima Chen, three kinds of ostracodes were analyzed. In this study, we concentrate on the relationships between molar ratios of Mg/Ca and temperature, and between molar ratios of Mg/Ca and salinity of the host water. We have found that the molar ratios of Mg/Ca of ostracize shells are positively correlated with the temperature of the host water, but negatively correlated with its salinity.

Recognition of sea-level change duringthe Neolithic period in the Jiangsu Area, East China

Based on the detailed analyses, multi-proxies such as AMS14C dating, elevation measurements with GPS-CORS, and the identification of marine micropaleontology are used to research the archaeological stratums archived in the Qingdun site of Haian, the Taozhuang site and Kaizhuang site of Dongtai, and the Luotuodun site of Yixing, respectively. The results show that the depth of 389–489 cm (13.1–8.5 cal ka BP, 1985 Yellow Sea Datum - 0.65–1.65 m) of Qingdun site, the depth of 156–230 cm (12.6–9.2 cal ka BP, 1985 Yellow Sea Datum 0.97–0.23 m) of Taozhuang site, the depth of 228–390 cm (10.3–7.8 cal ka BP, 1985 Yellow Sea Datum 0.03–1.59 m) of Kaizhaung site, and the depth of 255–279 cm (12.0–9.2 cal ka BP, 1985 Yellow Sea Datum 1.08–1.84 m) of Qingdun site are significant marine sedimentary strata. These indicate that there was still a shallow sea sedimentary environment from the beginning of the Holocene to 7.8 cal ka BP in the region of Haian and Dongtai in north Jiangsu. Meanwhile, there was also a shallow sea environment from the beginning of the Holocene to 9.2 cal ka BP to the west of Taihu Lake in south Jiangsu. These research findings not only improve the resolution of Holocene sea level changes, but also provide scientific clues and evidence for searching the early Neolithic sites in Jiangsu. In addition, the elevations of 62 ancient wells and 102 ash pits under the Chenghu Lake of Suzhou were measured using the GPS-CORS. These measured data suggest that in the Songze cultural period, the Liangzhu cultural period, the Xia-Shang-Zhou dynasties and the Warring States period, the 1985 Yellow Sea Datum of the top of the wells and ash pits are mostly in between 0 - 2 m, and their bottom elevations are mostly around - 3 m. In the six dynasties and the Song Dynasty, some 1985 Yellow Sea Datum of the top of the wells and ash pits are lower than - 1 m, while some bottom elevations are lower than - 4 m. This evidence demonstrates that the forming age of Chenghu Lake in Suzhou is in the period after the Song Dynasty.