Sedimentary Characteristics and Paleoenvironmental Significance of Early Cambrian Metazoan Reefs in Northern Margin of Upper Yangtze Block
-
摘要: 作为一种海洋高等级生态系统，生物礁在前寒武‒寒武纪过渡时期经历了重要转变，特别是后生动物礁的大规模出现对寒武纪早期生命与环境协同演化具有重要意义.以上扬子北缘多个寒武系仙女洞组含古杯生物礁剖面为例，开展了系统的沉积学特征分析.结果显示古杯动物既可以单独成礁，也可以与钙质微生物联合造礁，或者作为附礁生物保存于钙质微生物礁内部.古杯礁大部分具有低缓的外部形貌，障积结构发育且古杯化石保存较好，部分具亮晶胶结特征，以在正常浪基面附近和滩间环境发育最为典型.钙质微生物‒古杯礁与含古杯钙质微生物礁既可以单独发育，也可以在潮下带形成多个叠置状复合体；内部可见古杯被微生物黏附包绕或结壳，但礁胶结物少见.高能环境生物礁中古杯动物具有破碎状、异地搬运等特征，其原因可能与其个体较小，以及较薄的钙质骨骼还无法适应强水动力条件有关.另一方面，由于研究区滨海环境经常性陆源输入带来的较高营养条件更有利于微生物主导的生物礁发育，古杯在与其竞争过程中可能处于劣势.Abstract: As a complex marine ecosystem, reefs underwent a significant change in the composition of major builders during the Precambrian-Cambrian transition. The wide distribution of reef-building metazoans was likely a response to the co-evolution of life and oceans in the Early Cambrian. In this study, it performed a systematic sedimentological analysis on the archaeocyath-bearing reefs of the Xiannüdong Formation in the northern margin of the Upper Yangtze block. Petrological evidence indicates that the archaeocyaths may have contributed to the formation of the reefs individually or in combination with calcimicrobes. In some situations, archaeocyaths acted only as inhabitants of large thrombolitic reefs. The archaeocyath-dominated reefs are characterized by low-relief morphological units and partially cemented internal structures, and are thought to have formed in mid-ramp and inter-shoal environments with relatively low hydrodynamic conditions. Archaeocyath-calcimicrobial reefs and archaeocyath-bearing microbial reefs can form separately or develop as multiple stacked complexes in depositional successions thought to have formed in subtidal environments. Within the reef complexes, some archaeocyaths are coated or crusted by calcified microbes and few reefal cements are visible. The lack of archaeocyath-dominated reefs in shallow, high-energy conditions may be related to their small body size and thin skeletal structures, which cannot withstand the washing and destruction of waves and storms during this period. In addition, the relatively high nutrient levels in coastal environments, possibly caused by increased terrigenous input, may be more conducive to the development of calcimicrobe-dominated reef systems than archaeocyath-dominated reefs due to the greater nutrient competitiveness of the microbes.
-
Key words:
- archaeocyath /
- calcimicrobe /
- Xiannüdong Formation /
- Cambrian 3 /
- Hannan-Micangshan area /
- sedimentology /
- environmental geology
-
图 1 研究区寒武纪第三期古地理图及地层简表
古地理图据曾楷等(2020)、李红等(2021)修改，右下角图框为研究区在四川盆地的位置. 研究区寒武系第二统岩石地层参考自Li et al. (2023)
Fig. 1. Paleogeography and stratigraphic chart (Cambrian Age 3) of the study area
图 2 研究区仙女洞组剖面岩性柱状图及位置分布(修改自Li et al. (2021b))
Fig. 2. Lithostratigraphic columns of the Xiannüdong Formation and their distribution in the study area
图 3 研究区仙女洞组含古杯礁野外宏观特征
a.小型低缓古杯礁，杨家沟剖面仙女洞组底部；b.小型低缓古杯礁，朱家坝剖面仙女洞组底部；c.小型低缓平顶型古杯礁，唐家河剖面仙女洞组近顶部；d.单个大型隆起状厚层钙质微生物‒古杯礁，朱家坝剖面仙女洞组中部；e.大型巨厚层含古杯钙质微生物礁，沙滩剖面仙女洞组中上部；f.大型巨厚层含古杯钙质微生物礁，福成剖面仙女洞组中部
Fig. 3. Field photographs showing the characteristics of archaeocyath-bearing reefs in the Xiannüdong Formation of the study area
图 4 研究区仙女洞组造礁生物与附礁生物类型和特征
a.古杯动物与内碎屑颗粒，部分亮晶胶结，黄色箭头指示古杯，白色箭头指示内碎屑，杨家沟剖面仙女洞组底部；b.古杯与钙质微生物共生，黄色箭头指示古杯，红色箭头指示钙质微生物，部分作为古杯外壁结壳，大河坝剖面仙女洞组上部；c.规则古杯密集产出，横截面直径大部分在4~8 mm，唐家河剖面仙女洞组上部；d.大量破碎的古杯碎片异地混杂堆积(漂砾岩‒灰砾岩)，颗粒间主要为黄色粉砂‒黏土级陆源碎屑组分，沙滩剖面仙女洞组；e.含古杯钙质微生物礁，黄色箭头指示原地保存的古杯化石，白色箭头指示微生物凝块结构，福成剖面仙女洞组；f.古杯和钙质微生物共生(岩层底面)，黄色箭头指示密集发育的古杯动物，红色箭头指示钙质微生物形成的微型穹窿状结构，沙滩剖面仙女洞组
Fig. 4. Photographs showing the characteristics of reefal structures in the Xiannüdong Formation of the study area
图 5 研究区仙女洞组生物礁内部结构特征
a.不规则古杯(黄色箭头)，底部可见固着根(白色箭头)，杨家沟剖面；b.脑纹状不规则古杯(黄色箭头)，朱家坝剖面；c.规则古杯(右侧)、不规则古杯(左侧)与鲕粒(红色箭头)共存，周围含少量生屑(白色箭头)，福成剖面；d.古杯(黄色箭头)与共生的生物碎屑，红色箭头指示可能的小壳化石，沙滩剖面；e.古杯(黄色箭头)和小壳类(软舌螺)化石(红色箭头)，福成剖面；f.古杯和钙质微生物结壳(红色箭头)，杨家沟剖面；g.网状结构的钙质微生物格架，由葛万菌构成，沙滩剖面；h.附枝菌，灌木丛状分布，福成剖面；i.肾形菌，囊状外形，唐家河剖面；j.Tarthinia(黄色箭头)，朱家坝剖面；k.棘皮动物碎片(白色箭头)和三叶虫生物碎屑(红色箭头)，杨家沟剖面
Fig. 5. Photomicrographs showing the characteristics of reef-building and dwelling organisms of the Xiannüdong Formation of the study area
图 6 含古杯生物礁典型沉积序列
a.中缓坡小型低缓古杯礁沉积序列，杨家沟剖面；b.潮下带单个低缓古杯礁沉积序列，朱家坝剖面；c.潮下带穹窿状和厚层状生物礁复合体沉积序列，以钙质微生物‒古杯障积岩和含古杯钙质微生物黏结岩为主，福成剖面；d.滩间小型低缓平顶古杯礁沉积序列，唐家河剖面；除图中所列图例外，其他与图 2相同
Fig. 6. Sedimentary sequences and sea-level fluctuations of archaeocyath-bearing reefs
图 7 后生动物参与早期生物礁建造的主要特征
a.古杯动物丰度(Zhuravlev，1996)；b.钙质微生物属丰度(Zhuravlev，1996)；c.埃迪卡拉纪至早奥陶世生物礁中主要后生动物建造者(Lee and Riding, 2018). 注意钙质微生物属丰度变化在各个时期内部做了均化处理
Fig. 7. Distribution and characteristics of skeletal and microbial organisms within reef systems from the late Ediacaran to the Early Ordovician
图 8 研究区寒武纪第三期浅水沉积环境及生物礁分布特征
底图修改自Li et al. (2021b). FWWB.正常浪基面；SWB.风暴浪基面
Fig. 8. Cartoon showing the shallow-water depositional environments and the reef distributions of the study area during Cambrian Age 3
-
Brasier, M. D., 1990. Nutrients in the Early Cambrian. Nature, 347(6293): 521-522. https://doi.org/10.1038/347521b0 Burchette, T. P., Wright, V. P., 1992. Carbonate Ramp Depositional Systems. Sedimentary Geology, 79(1-4): 3-57. https://doi.org/10.1016/0037-0738(92)90003-A Deng, J. T., Li, F., Gong, Q. L., et al., 2021. Characteristics and Palaeoceanographic Significances of Microbialite Development in the Ediacaran-Cambrian Transition: A Case Study from Hannan-Micangshan Area. Journal of Palaeogeography, 23(5): 919-936 (in Chinese with English abstract). Duan, J. B., Mei, Q. H., Li, B. S., et al., 2019. Sinian-Early Cambrian Tectonic-Sedimentary Evolution in Sichuan Basin. Earth Science, 44(3): 738-755 (in Chinese with English abstract). Einsele, G., 2000. Sedimentation Rates and Organic Matter in Various Depositional Environments. In: Einsele, G., ed., Sedimentary Basins: Evolution, Facies, and Sediment Budget. Springer, Berlin, Heidelberg, 455-479. https://doi.org/10.1007/978-3-662-04029-4_10 Fan, J. S., Zhang, W., 1985. On the Basic Concept and Classification of Organic Reefs and Their Main Identifying Criteria. Acta Petrologica Sinica, 1(3): 45-59, 97 (in Chinese with English abstract). Gong, Q. L., Li, F., Su, C. P., et al., 2018. Characteristics, Distribution and Mechanisms of Fine-Grained Turbidite: A Case Study from the Cambrian Guojiaba Formation in Tangjiahe Section, Northern Sichuan Basin. Journal of Palaeogeography, 20(3): 349-364 (in Chinese with English abstract). Hallock, P., 2001. Coral Reefs, Carbonate Sediments, Nutrients, and Global Change. In: Stanley, G. D., ed., The History and Sedimentology of Ancient Reef Systems. Springer US, Boston, 387-427. https://doi.org/10.1007/978-1-4615-1219-6 Hicks, M., Rowland, S. M., 2009. Early Cambrian Microbial Reefs, Archaeocyathan Inter-Reef Communities, and Associated Facies of the Yangtze Platform. Palaeogeography, Palaeoclimatology, Palaeoecology, 281(1-2): 137-153. https://doi.org/10.1016/j.palaeo.2009.07.018 Humphreys, A. F., Purkis, S. J., Wan, C., et al., 2022. A New Foraminiferal Bioindicator for Long-Term Heat Stress on Coral Reefs. Journal of Earth Science, 33(6): 1451-1459. doi: 10.1007/s12583-021-1543-7 James, N. P., Gravestock, D. I., 1990. Lower Cambrian Shelf and Shelf Margin Buildups, Flinders Ranges, South Australial. Sedimentology, 37(3): 455-480. doi: 10.1111/j.1365-3091.1990.tb00147.x James, N. P., Wood, R., 2010. Reefs. In: James, N. P., Dalrymple, R. W., eds., Facies Models 4. Geological Association of Canada, St. John's, 421-447. Kiessling, W., Flügel, E., Golonka, J., 2002. Secular Variations in the Phanerozoic Reef Ecosystem. In: Kiessling, W., Flügel, E., Golonka, J., eds., Phanerozoic Reef Patterns. SEPM Special Publication, Tulsu, Oklahoma, 625-690. https://doi.org/10.2110/pec.02.72 Kruse, P. D., Gandin, A., Debrenne, F., et al., 1996. Early Cambrian Bioconstructions in the Zavkhan Basin of Western Mongolia. Geological Magazine, 133(4): 429-444. doi: 10.1017/S0016756800007597 Kruse, P. D., Zhuravlev, A. Y., James, N. P., 1995. Primordial Metazoan-Calcimicrobial Reefs: Tommotian (Early Cambrian) of the Siberian Platform. PALAIOS, 10(4): 291. https://doi.org/10.2307/3515157 Larcombe, P., Costen, A., Woolfe, K. J., 2001. The Hydrodynamic and Sedimentary Setting of Nearshore Coral Reefs, Central Great Barrier Reef Shelf, Australia: Paluma Shoals, a Case Study. Sedimentology, 48(4): 811-835. https://doi.org/10.1046/j.1365-3091.2001.00396.x Lee, J. H., Riding, R., 2018. Marine Oxygenation, Lithistid Sponges, and the Early History of Paleozoic Skeletal Reefs. Earth-Science Reviews, 181: 98-121. https://doi.org/10.1016/j.earscirev.2018.04.003 Li, F., Deng, J. T., Kershaw, S., et al., 2021a. Microbialite Development through the Ediacaran-Cambrian Transition in China: Distribution, Characteristics, and Paleoceanographic Implications. Global and Planetary Change, 205: 103586. https://doi.org/10.1016/j.gloplacha.2021.103586 Li, H., Li, F., Li, X., et al., 2021b. Development and Collapse of the Early Cambrian Shallow-Water Carbonate Factories in the Hannan-Micangshan Area, South China. Palaeogeography, Palaeoclimatology, Palaeoecology, 583: 110665. https://doi.org/10.1016/j.palaeo.2021.110665 Li, H., Li, F., Gong, Q. L., et al., 2021. Morphological Characteristics and Provenance Significance of Heavy Minerals in the Mixed Siliciclastic-Carbonate Sedimentation: A Case Study from the Xiannüdong Formation, Cambrian (Series 2), Northern Sichuan. Acta Sedimentologica Sinica, 39(3): 525-539 (in Chinese with English abstract). Li, Y. F., Li, F., 2022. How Did the Reefs Evolve during the Major Turning Point of Precambrian-Cambrian?. Earth Science, 47(10): 3853-3855 (in Chinese). Li, Y. L., Li, F., Kershaw, S., et al., 2023. Extensive Occurrences of Lower Cambrian Red Beds in South China: Composition, Characteristics, and Implications for Global Environmental Change. Marine and Petroleum Geology, 157: 106475. https://doi.org/10.1016/j.marpetgeo.2023.106475 Li, Y. L., Li, F., Li, X., et al., 2023. Factors Influencing the Composition of Shallow-Water Mixed Siliciclastic Carbonate Sedimentation from Cambrian Series 2: A Case Study on the Xiannüdong Formation of the Zhujiaba Section (Southern Shaanxi). Acta Sedimentologica Sinica, 1-16 (in Chinese with English abstract). Li, Y. L., Li, F., Lü, Y. J., et al., 2023. Petrographic Features and Paleoenvironmental Significance of the Lower Cambrian Reef inthe Xiannüdong Formation, Mian County, Southern Shaanxi. Acta Sedimentologica Sinica, 1-11 (in Chinese with English abstract). Liu, B. C., Qi, Y. A., Dai, M. Y., et al., 2021. Benthic Ecosystem Engineer after the Cambrian Explosion: An Example from Henan Province. Journal of Earth Science, 46(1): 148-161 (in Chinese with English abstract). Montaggioni, L. F., Braithwaite, C. J. R., 2009. Chapter Eight Reef Diagenesis. Quaternary Coral Reef Systems: History, Development Processes and Controlling Factors. Elsevier, Amsterdam, 323-372. https://doi.org/10.1016/s1572-5480(09)05008-8 Penny, A. M., Wood, R., Curtis, A., et al., 2014. Ediacaran Metazoan Reefs from the Nama Group, Namibia. Science, 344: 1504-1506. https://sci-hub.se/10.1126/science.1253393 doi: 10.1126/science.1253393 Pratt, B. R., Spincer, B. R., Wood, R. A., et al., 2000. Ecology and Evolution of Cambrian Reefs. In: Andrey, Z., Robert, R., eds., The Ecology of the Cambrian Radiation. Columbia University Press, New York, 254-274. https://doi.org/10.7312/zhur10612 Riding, R., 2002. Structure and Composition of Organic Reefs and Carbonate Mud Mounds: Concepts and Categories. Earth-Science Reviews, 58(1/2): 163-231. https://doi.org/10.1016/S0012-8252(01)00089-7 Rowland, S. M., Gangloff, R. A., 1988. Structure and Paleoecology of Lower Cambrian Reefs. PALAIOS, 3(2): 111. https://doi.org/10.2307/3514525 Rowland, S. M., Shapiro, R. S., 2002. Reef Patterns and Environmental Influences in the Cambrian and Earliest Ordovician. In: Kiessling, W., Flügel, E., Golonka, J., eds., Phanerozoic Reef Patterns. SEPM Special Publication, Tulsu, Oklahoma, 98-128. https://doi.org/10.2110/pec.02.72 Schroeder, J. H., Purser, B. H., 1986. Reef Diagenesis. Springer-Verlag, Berlin, Heidelberg, 455. https://doi.org/10.1007/978-3-642-82812-6 .Tang, H., Kershaw, S., Tan, X. C., et al., 2019. Sedimentology of Reefal Buildups of the Xiannüdong Formation (Cambrian Series 2), SW China. Journal of Palaeogeography, 8(1): 1-11. https://doi.org/10.1186/s42501-019-0022-x Webb, G. E., Baker, J. C., Jell, J. S., 1998. Inferred Syngenetic Textural Evolution in Holocene Cryptic Reefal Microbialites, Heron Reef, Great Barrier Reef, Australia. Geology, 26(4): 355. https://doi.org/10.1130/0091-7613(1998)0260355:isteih>2.3.co;2 doi: 10.1130/0091-7613(1998)0260355:isteih>2.3.co;2 Wood, R., Zhuravlev, A. Y., Debrenne, F., 1992. Functional Biology and Ecology of Archaeocyatha. PALAIOS, 7(2): 131. https://doi.org/10.2307/3514925 Xiang, L. W., Zhu, Z. L., Li, S. J., et al., 1999. Stratigraphic Lexicon of China. Cambrian System. Geological Publishing House, Beijing, 95 (in Chinese). Yang, A. H., 2005. The Early Cambrian Archaeocyaths and Their Extinction Event on the Yangtze Platform (Dissertation). Najing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Najing (in Chinese with English abstract). Yang, H. N., Mao, Y. Y., Pan, B., et al., 2016. Microfacies Sequences of the Early Cambrian (Series 2) Xiannvdong Formation Reefs in Southern Shaanxi Province, NW China. Acta Micropalaeontologica Sinica, 33(1): 75-86 (in Chinese with English abstract). Yang, Y. Y., Ye, J., 1996. Early Cambrian Reef from Yangjiagou, Xixiang, Shaanxi Province. Northwestern Geology, 17(2): 1-5 (in Chinese). Zeng, K., Li, F., Gong, Q. L., et al., 2020. Characteristics and Paleoenvironmental Significance of Mixed Siliciclastic-Carbonate Sedimentation in the Xiannüdong Formation, Cambrian (Series 2): A Case Study from the Tangjiahe Section, Wangcang, Northern Sichuan. Acta Sedimentologica Sinica, 38(1): 166-181 (in Chinese with English abstract). Zhang, M. Q., Hong, J., Choh, S. J., et al., 2017. Thrombolite Reefs with Archaeocyaths from the Xiannüdong Formation (Cambrian Series 2), Sichuan, China: Implications for Early Paleozoic Bioconstruction. Geosciences Journal, 21(5): 655-666. https://doi.org/10.1007/s12303-017-0011-y Zhuravlev, A. Y., 1996. Reef Ecosytem Recovery after the Early Cambrian Extinction. Geological Society, London, Special Publications, 102(1): 79-96. https://doi.org/10.1144/gsl.sp.1996.001.01.06 Zhuravlev, A. Y., Wood, R., 1995. Lower Cambrian Reefal Cryptic Communities. Palaeontology, 38: 443-470. https://www.biodiversitylibrary.org/part/174228 邓嘉婷, 李飞, 龚峤林, 等, 2021. 埃迪卡拉纪‒寒武纪之交微生物岩特征对比及古海洋学意义: 以汉南‒米仓山地区为例. 古地理学报, 23(5): 919-936. https://www.cnki.com.cn/Article/CJFDTOTAL-GDLX202105006.htm 段金宝, 梅庆华, 李毕松, 等, 2019. 四川盆地震旦纪‒早寒武世构造‒沉积演化过程. 地球科学, 44(3): 738-755. doi: 10.3799/dqkx.2018.335 范嘉松, 张维, 1985. 生物礁的基本概念、分类及识别特征. 岩石学报, 1(3): 45-59. https://www.cnki.com.cn/Article/CJFDTOTAL-YSXB198503004.htm 龚峤林, 李飞, 苏成鹏, 等, 2018. 细粒浊积岩特征、分布及发育机制: 以川北唐家河剖面寒武系郭家坝组为例. 古地理学报, 20(3): 349-364. https://www.cnki.com.cn/Article/CJFDTOTAL-GDLX201803001.htm 李红, 李飞, 龚峤林, 等, 2021. 混积岩中重矿物形貌学特征及物源意义——以川北寒武系第二统仙女洞组为例. 沉积学报, 39(3): 525-539. https://www.cnki.com.cn/Article/CJFDTOTAL-CJXB202103003.htm 李杨凡, 李飞, 2022. 前寒武‒寒武纪重大转折期生物礁是如何演化的?. 地球科学, 47(10): 3853-3855. doi: 10.3799/dqkx.2022.838 李怡霖, 李飞, 李翔, 等, 2023. 寒武系第二统浅水混合沉积发育特征及影响因素——以陕南朱家坝剖面仙女洞组为例. 沉积学报, 1-16. 李雅兰, 李飞, 吕月建, 等, 2023. 陕南勉县寒武系仙女洞组生物礁岩相学及古环境分析. 沉积学报, 1-11. 刘炳辰, 齐永安, 代明月, 等, 2021. 寒武纪生物大爆发之后的底栖生态系统工程建造者: 以河南地区为例. 地球科学, 46(1): 148-161. doi: 10.3799/dqkx.2019.245 项礼文, 朱兆玲, 李善姬, 等, 1999. 中国地层典 寒武系. 北京: 地质出版社, 95. 杨爱华, 2005. 扬子地台早寒武世古杯动物群及其灭绝事件(博士学位论文). 南京: 中国科学院南京地质古生物研究所. 杨慧宁, 毛颖颜, 潘兵, 等, 2016. 陕南寒武纪早期仙女洞组生物礁灰岩微相序列. 微体古生物学报, 33(1): 75-86. https://www.cnki.com.cn/Article/CJFDTOTAL-WSGT201601009.htm 杨友运, 叶俭, 1996. 陕西西乡杨家沟早寒武世的生物礁. 西北地质, 17(2): 1-5. https://www.cnki.com.cn/Article/CJFDTOTAL-XBDI602.000.htm 曾楷, 李飞, 龚峤林, 等, 2020. 寒武系第二统仙女洞组混合沉积特征及古环境意义——以川北旺苍唐家河剖面为例. 沉积学报, 38(1): 166-181. https://www.cnki.com.cn/Article/CJFDTOTAL-CJXB202001014.htm -
下载:
点击查看大图
计量
- 文章访问数: 302
- HTML全文浏览量: 470
- PDF下载量: 55
- 被引次数: 0
