Chen Yifeng

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  • Article
    Ages and magnetic structures of the South China Sea constrained by deep tow magnetic surveys and IODP Expedition 349
    (John Wiley & Sons, 2014-12-27) Li, Chun-Feng ; Xu, Xing ; Lin, Jian ; Sun, Zhen ; Zhu, Jian ; Yao, Yongjian ; Zhao, Xixi ; Liu, Qingsong ; Kulhanek, Denise K. ; Wang, Jian ; Song, Taoran ; Zhao, Junfeng ; Qiu, Ning ; Guan, Yongxian ; Zhou, Zhiyuan ; Williams, Trevor ; Bao, Rui ; Briais, Anne ; Brown, Elizabeth A. ; Chen, Yifeng ; Clift, Peter D. ; Colwell, Frederick S. ; Dadd, Kelsie A. ; Ding, Weiwei ; Almeida, Ivan Hernandez ; Huang, Xiao-Long ; Hyun, Sangmin ; Jiang, Tao ; Koppers, Anthony A. P. ; Li, Qianyu ; Liu, Chuanlian ; Liu, Zhifei ; Nagai, Renata H. ; Peleo-Alampay, Alyssa ; Su, Xin ; Tejada, Maria Luisa G. ; Trinh, Hai Son ; Yeh, Yi-Ching ; Zhang, Chuanlun ; Zhang, Fan ; Zhang, Guo-Liang
    Combined analyses of deep tow magnetic anomalies and International Ocean Discovery Program Expedition 349 cores show that initial seafloor spreading started around 33 Ma in the northeastern South China Sea (SCS), but varied slightly by 1–2 Myr along the northern continent-ocean boundary (COB). A southward ridge jump of ∼20 km occurred around 23.6 Ma in the East Subbasin; this timing also slightly varied along the ridge and was coeval to the onset of seafloor spreading in the Southwest Subbasin, which propagated for about 400 km southwestward from ∼23.6 to ∼21.5 Ma. The terminal age of seafloor spreading is ∼15 Ma in the East Subbasin and ∼16 Ma in the Southwest Subbasin. The full spreading rate in the East Subbasin varied largely from ∼20 to ∼80 km/Myr, but mostly decreased with time except for the period between ∼26.0 Ma and the ridge jump (∼23.6 Ma), within which the rate was the fastest at ∼70 km/Myr on average. The spreading rates are not correlated, in most cases, to magnetic anomaly amplitudes that reflect basement magnetization contrasts. Shipboard magnetic measurements reveal at least one magnetic reversal in the top 100 m of basaltic layers, in addition to large vertical intensity variations. These complexities are caused by late-stage lava flows that are magnetized in a different polarity from the primary basaltic layer emplaced during the main phase of crustal accretion. Deep tow magnetic modeling also reveals this smearing in basement magnetizations by incorporating a contamination coefficient of 0.5, which partly alleviates the problem of assuming a magnetic blocking model of constant thickness and uniform magnetization. The primary contribution to magnetic anomalies of the SCS is not in the top 100 m of the igneous basement.
  • Article
    Seismic stratigraphy of the central South China Sea basin and implications for neotectonics
    (John Wiley & Sons, 2015-03-16) Li, Chun-Feng ; Li, Jiabiao ; Ding, Weiwei ; Franke, Dieter ; Yao, Yongjian ; Shi, Hesheng ; Pang, Xiong ; Cao, Ying ; Lin, Jian ; Kulhanek, Denise K. ; Williams, Trevor ; Bao, Rui ; Briais, Anne ; Brown, Elizabeth A. ; Chen, Yifeng ; Clift, Peter D. ; Colwell, Frederick S. ; Dadd, Kelsie A. ; Hernandez-Almeida, Ivan ; Huang, Xiao-Long ; Hyun, Sangmin ; Jiang, Tao ; Koppers, Anthony A. P. ; Li, Qianyu ; Liu, Chuanlian ; Liu, Qingsong ; Liu, Zhifei ; Nagai, Renata H. ; Peleo-Alampay, Alyssa ; Su, Xin ; Sun, Zhen ; Tejada, Maria Luisa G. ; Trinh, Hai Son ; Yeh, Yi-Ching ; Zhang, Chuanlun ; Zhang, Fan ; Zhang, Guo-Liang ; Zhao, Xixi
    Coring/logging data and physical property measurements from International Ocean Discovery Program Expedition 349 are integrated with, and correlated to, reflection seismic data to map seismic sequence boundaries and facies of the central basin and neighboring regions of the South China Sea. First-order sequence boundaries are interpreted, which are Oligocene/Miocene, middle Miocene/late Miocene, Miocene/Pliocene, and Pliocene/Pleistocene boundaries. A characteristic early Pleistocene strong reflector is also identified, which marks the top of extensive carbonate-rich deposition in the southern East and Southwest Subbasins. The fossil spreading ridge and the boundary between the East and Southwest Subbasins acted as major sedimentary barriers, across which seismic facies changes sharply and cannot be easily correlated. The sharp seismic facies change along the Miocene-Pliocene boundary indicates that a dramatic regional tectonostratigraphic event occurred at about 5 Ma, coeval with the onsets of uplift of Taiwan and accelerated subsidence and transgression in the northern margin. The depocenter or the area of the highest sedimentation rate switched from the northern East Subbasin during the Miocene to the Southwest Subbasin and the area close to the fossil ridge in the southern East Subbasin in the Pleistocene. The most active faulting and vertical uplifting now occur in the southern East Subbasin, caused most likely by the active and fastest subduction/obduction in the southern segment of the Manila Trench and the collision between the northeast Palawan and the Luzon arc. Timing of magmatic intrusions and seamounts constrained by seismic stratigraphy in the central basin varies and does not show temporal pulsing in their activities.
  • Preprint
    Methane-derived authigenic carbonates from the northern Gulf of Mexico — MD02 Cruise
    ( 2007-05-25) Chen, Yifeng ; Matsumoto, Ryo ; Paull, Charles K. ; Ussler, William ; Lorenson, Thomas D. ; Hart, Patrick E. ; Winters, William J.
    Authigenic carbonates were sampled in piston cores collected from both the Tunica Mound and the Mississippi Canyon area on the continental slope of the northern Gulf of Mexico during a Marion Dufresne cruise in July 2002. The carbonates are present as hardgrounds, porous crusts, concretions or nodules and shell fragments with or without carbonate cements. Carbonates occurred at gas venting sites which are likely to overlie gas hydrates bearing sediments. Electron microprobe, X-ray diffraction (XRD) and thinsection investigations show that these carbonates are high-Mg calcite (6 - 21 mol % MgCO3), with significant presence of framboidal pyrite. All carbonates are depleted in 13C (δ13C = -61.9 to -31.5 ‰ PDB) indicating that the carbon is derived mainly from anaerobic methane oxidation (AMO). Age estimates based on 14C dating of shell fragments and on regional sedimentation rates indicate that these authigenic carbonates formed within the last 1,000 yr in the Mississippi Canyon and within 5,500 yr at the Tunica Mound. The oxygen isotopic composition of carbonates ranges from +3.4 to +5.9 ‰ PDB. Oxygen isotopic compositions and Mg2+ contents of carbonates, and present in-situ temperatures of bottom seawater/sediments, show that some of these carbonates, especially from a core associated with underlying massive gas hydrates precipitated in or near equilibrium with bottom-water. On the other hand, those carbonates more enriched in 18O are interpreted to have precipitated from 18O-rich fluids which are thought to have been derived from the dissociation of gas hydrates. The dissociation of gas hydrates in the northern Gulf of Mexico within the last 5,500 yr may be caused by nearby salt movement and related brines.