Two out of three ain’t bad: Dealing with proxy paucity when correlating the base of the Cambrian
- 1Shaanxi Key Laboratory of Early Life and Environments, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi'an 710069, China. (timothy.topper@nwu.edu.cn)
- 2Department of Palaeobiology, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden
- 3Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, New South Wales 2351, Australia
- 4Institute of Paleontology, Mongolian Academy of Sciences, Ulaanbaatar, Mongolia
- 5State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
- 6Frontiers Science Centre for Deep Ocean Multispheres and Earth Systems, Key Lab of Submarine Geosciences and Prospecting Techniques, MOE and College of Marine Geosciences, Ocean University of China, Qingdao, 266100, China
- 7School of Arts and Sciences, National University of Mongolia, Ulaanbaatar 14200, Mongolia
Global Boundary Stratotype Section and Points (GSSP’s) are often regarded as immutable points, that once ratified should “remain fixed in spite of discoveries stratigraphically above and/or below” (Cowie, 1986, p. 79). The Precambrian–Cambrian boundary, defined at Fortune Head by the FAD of the trace fossil Treptichnus pedum, has been a source of controversy and debate since its ratification. Treptichnus pedum has proven to be a difficult marker to apply to global correlation, and lack of other markers at Fortune Head (skeletal fossils, chemostratigraphic, magnetostratigraphic or radiometric data) has prompted the use of other “unofficial” indicators of the Precambrian–Cambrian boundary in many sections around the world. δ13C chemostratigraphy has become a standard global correlation tool, and the integration of δ13C isotopes with other “multi-proxy” data is an approach that is becoming increasingly adopted. Discoveries and advances in such methods and techniques demonstrate that new data can (and should) enable the fine-tuning of stratigraphic boundaries. Recent work in southwestern Mongolia through the Precambrian–Cambrian boundary section at Bayan Gol demonstrates the utility of multi-proxy stratigraphic data to defining and correlating the base of the Cambrian. Here, two proxies are used in concert to identify the Precambrian–Cambrian boundary; the first occurrence of the small shelly fossil Protohertzina anabarica and the nadir of the BACE (δ13C excursion). This section demonstrates 1) the value of carbonates in their capacity to preserve a wider variety of stratigraphic proxies than siliciclastics, 2) the importance of systematically measured and sampled stratigraphic sections (rather than composite sections) for regional and global correlation and 3) the need for a redefined Cambrian GSSP, with a supporting ASSP as a pathway toward global correlation of the base of the Cambrian.
How to cite: Topper, T., Betts, M., Dorjnamjaaa, D., Li, G., Li, L., Altanshagai, G., Enhkbaatar, B., and Skovsted, C.: Two out of three ain’t bad: Dealing with proxy paucity when correlating the base of the Cambrian, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5782, https://doi.org/10.5194/egusphere-egu23-5782, 2023.
