富有机质细粒沉积岩往往为深水沉积,可以较为完整的保存沉积时期的古气候、水体性质和古生态等信息。尤其在早侏罗世、早白垩世、晚白垩世和古新世-渐新世,全球发生了一系列的缺氧、温室-热室、古火灾、水陆生态系统快速演替、碳释放和碳富集等热点事件,而这些全球性及区域事件在富有机质细粒沉积岩中可以得到有效的保存。
针对上述科学问题,6165cc金沙总站检测中心刘招君教授团队的孙平昌副教授及研究生王君贤、李元吉、陶连馨和王灼等人,对东北地区抚顺盆地始新统巨厚含煤-含油页岩层系、新疆准噶尔盆地二叠纪芦草沟组巨厚油页岩层序和新疆大长沟盆地早侏罗世八道湾组含油页岩-烛煤层系开展了古环境恢复,取得以下阶段性进展:
进展1—定量恢复了东北地区始新世和新疆地区早侏罗世古大气CO2浓度
基于有机碳同位素及饱和烃单体碳同位素,确定陆源有机质碳同位素值,利用古大气二氧化碳估算公式,计算出抚顺盆地极热时期pCO2在2500-1000ppm左右,其中以ETM2时期二氧化碳浓度最高(图1);估算出早侏罗世Sinemurian的pCO2介于1815-625ppm。并初步揭示早侏罗世和始新世二氧化碳浓度升高与地表有机质氧化和火山事件有关。
B同位素(Pearson et al.,2009;Pearson and Palmer,2000),银杏(Retallack,2001;Retallack,2009;Beerling et al.,2009;Beerling and Royer,2002;Royer,2003;Smith et al.,2010),古土壤(Koch et al.,1992;Cerling,1992;Sinha and Stott,1994;Ekart et al.,1999;Royer et al.,2001a;Nordt et al.,2002),气孔(Royer et al.,2001b;Royer,2003;Doria et al.,2011;Maxbauer et al.,2014;Barclay and Wing,2016),C3植物(Cui and Schubert,2016)
进展2-建立抚顺盆地始新统天文年代标尺,识别出多期极热事件,刻画了极热事件对陆地生态的影响
在古城子火山灰绝对年龄、生物和古地磁年龄基础上,开展了米氏旋回分析,建立了天文年代标尺,并结合CIE,在抚顺盆地始新统识别出ETM2、ETM3、EECO等极热事件,同时结合磁化率和色度与同位素的变化趋势、聚类分析,确定磁化率是进行古气候分析的有效指标。根据孢粉组合特征,确定东北地区始新统极热时期古气温上升2-5℃,降雨量增加了200-600mm,同时高温事件促使针叶树等木本植物的生长,促进了碳封存,揭示出始新世气候变暖的短期爆发导致亚洲中纬度地区植被发生重大变化,改变了景观,并改变了区域水文状况(图2)。
进展3-揭示了相对浅水环境中有机质富集控制因素
根据我国陆相盆地油页岩赋存特征,识别出深水和浅水两种类型的油页岩矿床,并以抚顺盆地西露天组和大长沟盆地八道湾组浅水油页岩为实例开展有机质富集机制研究,总体表明水陆生态变化及有机质来源的更替(图3)、浅水蒸发咸化是控制浅水型油页岩发育厚度、品质和展布特征的关键因素。
进展4-揭示了富有机质细粒沉积岩形成的水动力条件
油页岩层系中往往发育碎屑颗粒纹层(碎屑颗粒含量A(体积百分含量)≥75vol.%)、富碎屑颗粒纹层(75>A≥50 vol.%)、富黏土质纹层(50>A≥25 vol.%)和黏土质纹层(A<25 vol.%)。通过开展单纹层粒度分析,发现纹层中碎屑颗粒多以递变悬浮和均匀悬浮搬运为主,多受季节性洪水、地表径流注入和远端浊积岩末端效应的影响,此外风携沉积也是部分细粒沉积物的主要来源(图4)。
上述系列研究成果发表在国际地学知名期刊《Palaeogeography,Palaeoclimatology,Palaeoecology》、《Marine and Petroleum Geology》及《Geomechanics and Geophysics for Geo-Energy and Geo-Resources》、《ACS Omega》、《古地理学报》等期刊上。该系列研究受国家自然基金(41772092)资助。
论文:
1) Yuanji Li(李元吉)*,Pingchang Sun(孙平昌)*,Howard J.Falcon-Lang,Zhaojun Liu(刘招君),Baoyong Zhang(张保勇),Qiang Zhang(张强),Junxian Wang(王君贤),Yinbo Xu(徐银波). Eocene hyperthermal events drove episodes of vegetation turnover in the Fushun Basin, northeast China: Evidence from a palaeoclimate analysis of palynological assemblages. Palaeogeography, Palaeoclimatology, Palaeoecology, 2022, 111317.
论文链接:https://doi.org/10.1016/j.palaeo.2022.111317
2) Junxian Wang(王君贤),Pingchang Sun(孙平昌)*,Yueyue Bai(白悦悦),zhaojun Liu(刘招君),Rihui Cheng(程日辉),Yuanji Li(李元吉). Carbon isotopes of n-alkanes allow for estimation of the pCO2 pressure in the Early Jurassic - A case study from lacustrine shale and cannel boghead in the Dachanggou Basin, Xinjiang, North west China. Palaeogeography, Palaeoclimatology, Palaeoecology,607,111252.
论文链接:https://doi.org/10.1016/j.palaeo.2022.111252
3) Lianxin Tao(陶连馨),Pingchang Sun(孙平昌)*,Yinbo Xu(徐银波). Sedimentary origin of fine-grained rocks in the Permian Lucaogou Formation in the southern Junggar Basin: implications from grain size analysis. Geomechanics and Geophysics for Geo-Energy and Geo-Resources,2022,192.
论文链接:https://doi.org/10.1007/s40948-022-00475-2
4) Yuanji Li(李元吉),Pingchang Sun(孙平昌)*,Zhaojun Liu(刘招君),Yueyue Bai(白悦悦),Lin Ma(马琳),Junxian Wang(王君贤),Yinbo Xu(徐银波),Rong Liu(柳蓉). Quantitative reconstruction of atmospheric pCO2 sources during Eocene hyperthermal events based on data from the Fushun Basin, Northeast China. Palaeogeography, Palaeoclimatology, Palaeoecology,2022,601,111099.
论文链接:https://doi.org/10.1016/j.palaeo.2022.111099
5) Zhuo Wang(王灼),Pingchang Sun(孙平昌)*,Jiangfeng Du(杜江峰),Yuanji Li(李元吉),Junxian Wang(王君贤),Liyun Hou(侯丽云),Yinbo Xu(徐银波),Yueyue Bai(白悦悦). Eocene Paleoclimate Evolution under the Background of Warmhouse–Hothouse Conditions in the Continental Fushun Basin: Implications from Magnetic Susceptibility and Color Reflectance. ACS Omega,2022, 28(7):24614–24625.
论文链接:https://doi.org/10.1021/acsomega.2c02445
6) Yuanji Li(李元吉),Pingchang Sun(孙平昌)*,Zhaojun Liu(刘招君),Yueyue Bai(白悦悦),Yinbo Xu(徐银波),Lin Ma(马琳),Rong Liu(柳蓉). Eocene hyperthermal events in the terrestrial system: Geochronological and astrochronological constraints in the Fushun Basin, NE China. Marine and Petroleum Geology,2022, 139, 105604.
论文链接: https://doi.org/10.1016/j.marpetgeo. 2022.105604
7) Junxian Wang(王君贤),Pingchang Sun(孙平昌)*,Zhaojun Liu(刘招君),Yuanji Li(李元吉). Characteristics and genesis of lacustrine laminar coal and oil shale: A case study in the Dachanggou Basin, Xinjiang, Northwest China. Marine and Petroleum Geology,2021,126,104924.
论文链接:https://doi.org/10.1016/j. marpetgeo.2021.104924
8) Yuanji Li(李元吉),Pingchang Sun(孙平昌)*,Zhaojun Liu(刘招君),Yinbo Xu(徐银波),Rong Liu(柳蓉),Lin Ma(马琳). Factors controlling the distribution of oil shale layers in the Eocene Fushun Basin, NE China. Marine and Petroleum Geology,2021,134,105350.
论文链接:https://doi.org/10.1016/j.marpetgeo. 2021.105350
9) 刘招君,孙平昌*. 中国陆相盆地油页岩形成环境与成矿机制. 古地理学报,2021,23(1):1-17.
论文链接:https:// doi: 10.7605 /gdlxb.2021.01.001