|
Original Article |
1 Department of Earth Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3YE, UK
2 Present address: Total Exploration & Production, Avenue Larribau, 64018 Pau, France (e-mail: andrew.barnett{at}total.com)
3 BG Group, 100 Thames Valley Park Drive, Reading RG6 1PT, UK
The Mississippian–Pennsylvanian Global Stratotype Section and Point (GSSP) are hosted within a shallow-water, dominantly carbonate succession in the lower part of the Bird Spring Formation at Arrow Canyon, Nevada, USA. The boundary is marked by the first appearance datum (FAD) of the conodont Declinognathodus noduliferus sensu lato. It is shown that the boundary interval is punctuated by numerous subaerial hiatuses represented by palaeokarstic surfaces and palaeosols, which divide strata at this location into fourth-order glacio-eustatic cycles. A well-developed palaeosol horizon occurs <1 m above the FAD of D. noduliferus. It also coincides with a very marked facies change and a second-order shift in cycle-stacking patterns. These characteristics violate International Commission on Stratigraphy guidelines, which state that GSSPs should be chosen in sections showing continuous sedimentation and lacking vertical facies changes at or near the boundary. Because the Mid-Carboniferous is an icehouse interval, cyclostratigraphy is a powerful tool for high-resolution correlation. A comparison of the cyclostratigraphy of Mid-Carboniferous strata at Arrow Canyon and in northern England indicates that a large number of glacio-eustatic sea-level oscillations are not recorded at Arrow Canyon and that this section contains over 25 missed beats of Milankovitch band duration equating to a hiatus of
1 Ma.
