Characterization of the negative carbon isotope shift in segment C2,its global implications as a harbinger of OAEla

作     者：Jander SOCORRO Florentin J-M. R. MAURRASSE Yosmel SANCHEZ-HERNANDEZ 

作者机构：Department Earth and Environment Florida International University 11200 SW 8 Street Miami FL 33199 USA 

出 版 物：《Science China Earth Sciences》 (中国科学（地球科学英文版）)

年 卷 期：2017年第60卷第1期

页      面：30-43页

核心收录：

学科分类：070902[理学-地球化学] 070903[理学-古生物学与地层学(含：古人类学)] 0709[理学-地质学] 07[理学] 

基　　金：a contribution of IGCP Project 609 "Climate-environmental deteriorations during greenhouse phases:Causes ana consequences of short-term Cretaceous sea-level changes " 

主　　题：Oceanic Anoxic Event la (OAEla) Aptian Organy Basin Chemostratigraphy Pyrenees 

摘      要：Lower Cretaceous C-isotope records show intermittent negative/positive spikes, and consistent patterns of coevalchemostratigraphic curves thus document shifts that signal simultaneous responses of temporal changes in the global carbon reservoir. The standard pattern registered by the δ13Corg and δ13Ccarb in Lower Aptian sediments includes distinct isotope segments C1 to C8 （Menegatti et al., 1998）. In the E1 Pui section, Organy Basin, Spain, C-isotope segment C2 is the longest interval preceding segments C3-C6 associated with oceanic anoxic event la （OAE la）, and reveals a distinct negative shift of-1.8‰ to -2.23‰ defining the C-isotope pattern within that interval. Total inorganic carbon （TIC）, total organic carbon （TOC）, δ13Corg, microfacies, n-alkanes show no difference before, during, or after the negative inflection. The biomarkers indicate that organic matter （OM） mainly originates from algal/microbial sources because short-chain length homologues （〈 nCtg） dominate, nC2o through nC25 indicate some contribution from aquatic vegetation, but little from higher plants （〉nC20, as also suggested by the terrestrial/aquatic ratio ofn-alkanes or （TAR） = [（nf27＋nf29＋nC31）/（nC15＋nCt7＋rlCt9）] （averages 0.085）. We suggest that conjoint pulses of contemporaneous LIPs （Ontong Java） and massive explosive volcanism in northeast Asia, the Songliao Basin （SB-V）, best conform to plausible causes of the negative intra-C2 carbon isotopic excursion （CIE） at that time. Because of its apparent common occurrence the intra-C2 inflection could be a useful marker harbinger to the more pronounced CIE C3, the hallmark of OAE 1 a.