Abstract
The end-Triassic mass extinction is one of the big five extinction events in Phanerozoic Earth history. It is linked with the emplacement of the Central Atlantic Magmatic Province and a host of interconnected environmental and climatic responses that caused profound deterioration of terrestrial and marine biospheres. Current understanding, however, is hampered by (i) a geographically limited set of localities and data; (ii) incomplete stratigraphic records caused by low relative sea-level in European sections during the Late Triassic and earliest Jurassic; and (iii) major discrepancies in the estimated duration of the latest Triassic Rhaetian that limit spatiotemporal evaluation of climatic and biotic responses locally and globally. Here, we investigate the Late Triassic–Early Jurassic time interval from a stratigraphically well-preserved sedimentary succession deposited in tropical oceanic Panthalassa. We present diverse new data from the lower McCarthy Formation exposed at Grotto Creek (Wrangell Mountains, southern Alaska), including ammonoid, bivalve, hydrozoan, and conodont biostratigraphy; organic carbon isotope (δ13Corg) stratigraphy; and CA-ID TIMS zircon U–Pb dates. These data are consistent with a Norian-Rhaetian Boundary (NRB) of ∼209 Ma, providing new evidence to support a long duration of the Rhaetian. They also constrain the Triassic-Jurassic boundary (TJB) to a ∼6 m interval in the section. Our TJB δ13Corg record from Grotto Creek, in conjunction with previous data, demonstrates consistent features that not only appear correlative on a global scale but also shows local heterogeneities compared to some Tethyan records. Notably, smaller excursions within a large negative carbon isotope excursion [NCIE] known from Tethyan localities are absent in Panthalassan records. This new comparative isotopic record becomes useful for (i) distinguishing regional overprinting of the global signal; (ii) raising questions about the ubiquity of smaller-scale NCIEs across the TJB; and (iii) highlighting the largely unresolved regional vs. global scale of some presumed carbon cycle perturbations. These paleontological and geochemical data establish the Grotto Creek section as an important Upper Triassic to Lower Jurassic succession due to its paleogeographic position and complete marine record. Our record represents the best documentation of the NRB and TJB intervals from Wrangellia, and likely the entire North American Cordillera.
| Original language | English |
|---|---|
| Article number | 117262 |
| Pages (from-to) | 1-14 |
| Journal | Earth and Planetary Science Letters |
| Volume | 577 |
| DOIs | |
| Publication status | Published - 1 Jan 2022 |
Bibliographical note
Funding Information:We thank Mark Miller, Morgan Gantz, Desiree Ramirez, and Danny Rosencrans at the Wrangell - St. Elias National Park and Preserve (collections permit numbers WRST-2017-SCI-0004 and WRST-2018-SC1-0005) for access to Grotto Creek and continued support for this project; Paul Claus at Ultima Thule Charters for air support; and Robert B. Blodgett for logistical support. AHC acknowledges Lauren Jaskot for fossil photography. We thank detailed comments and critiques by two anonymous reviewers which led to an improved manuscript. This work was supported by grants from the National Geographic Society ( NGS-9973-16 ) to AHC and the National Science Foundation ( EAR-2026926 ) to AHC, JDO, and BCG. BCG and SMM would like to thank the Virginia Tech College of Science Dean's Discovery Fund for financial support of the fieldwork; SMM would like to thank the Virginia Tech Department of Geosciences , Geological Society of America , Alaska Geological Society , SEPM Society for Sedimentary Geology , and the Paleontological Society for student grants used to fund this work; TRT would like to thank the College of Charleston Faculty Research & Development Committee for financial support of the fieldwork; JDO acknowledges Florida State University Planning Grant and NASA Exobiology ( 80NSSC18K1532 ) for financial support of the fieldwork and support by the National High Magnetic Field Laboratory (Tallahassee, Florida), which is funded by the National Science Foundation Cooperative Agreement No. DMR1644779 and the State of Florida; JPTA and YPV would like to thank the Molengraaff fund and SEPM for financial support of the fieldwork; MA would like to thank the DFG -funded Research Unit TERSANE ( FOR 2332 : Temperature-related Stressors as a Unifying Principle in Ancient Extinctions) for support and Michael Hautmann for discussion of Triassic bivalve taxonomy; MG would like to thank the Geological Survey of Canada GEM 2 Program for financial support of the fieldwork and conodont analyses; JP acknowledges support from the National Research, Development and Innovation Office (Grant No. NN 128702 and K135309 ); RF acknowledges H. Lin for mineral separation, T. Ockerman and J. Cho for grain mounting and imaging, and M. Amini for laser set-up; and JMT acknowledges the American Chemical Society for financial support of reconnaissance fieldwork, and C. Slaughter and J. Witmer for field assistance.
Funding Information:
We thank Mark Miller, Morgan Gantz, Desiree Ramirez, and Danny Rosencrans at the Wrangell - St. Elias National Park and Preserve (collections permit numbers WRST-2017-SCI-0004 and WRST-2018-SC1-0005) for access to Grotto Creek and continued support for this project; Paul Claus at Ultima Thule Charters for air support; and Robert B. Blodgett for logistical support. AHC acknowledges Lauren Jaskot for fossil photography. We thank detailed comments and critiques by two anonymous reviewers which led to an improved manuscript. This work was supported by grants from the National Geographic Society (NGS-9973-16) to AHC and the National Science Foundation (EAR-2026926) to AHC, JDO, and BCG. BCG and SMM would like to thank the Virginia Tech College of Science Dean's Discovery Fund for financial support of the fieldwork; SMM would like to thank the Virginia Tech Department of Geosciences, Geological Society of America, Alaska Geological Society, SEPM Society for Sedimentary Geology, and the Paleontological Society for student grants used to fund this work; TRT would like to thank the College of Charleston Faculty Research & Development Committee for financial support of the fieldwork; JDO acknowledges Florida State University Planning Grant and NASA Exobiology (80NSSC18K1532) for financial support of the fieldwork and support by the National High Magnetic Field Laboratory (Tallahassee, Florida), which is funded by the National Science Foundation Cooperative Agreement No. DMR1644779 and the State of Florida; JPTA and YPV would like to thank the Molengraaff fund and SEPM for financial support of the fieldwork; MA would like to thank the DFG-funded Research Unit TERSANE (FOR 2332: Temperature-related Stressors as a Unifying Principle in Ancient Extinctions) for support and Michael Hautmann for discussion of Triassic bivalve taxonomy; MG would like to thank the Geological Survey of Canada GEM 2 Program for financial support of the fieldwork and conodont analyses; JP acknowledges support from the National Research, Development and Innovation Office (Grant No. NN 128702 and K135309); RF acknowledges H. Lin for mineral separation, T. Ockerman and J. Cho for grain mounting and imaging, and M. Amini for laser set-up; and JMT acknowledges the American Chemical Society for financial support of reconnaissance fieldwork, and C. Slaughter and J. Witmer for field assistance.
Publisher Copyright:
© 2021 Elsevier B.V.
Keywords
- CAMP large igneous province
- Norian-Rhaetian boundary
- Panthalassa
- Triassic-Jurassic boundary
- Wrangellia
- stable carbon isotopes
