| 1. |
- Jensen, Sören, et al.
(författare)
-
Trace fossils across the Ediacaran–Cambrian boundary on the Digermulen Peninsula, Arctic Norway
- 2017
-
Ingår i: ISECT 2017. - : Memorial University, St. Johns.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digermulen Peninsula, Arctic Norway, contains one of the most complete Ediacaran–Cambrian sedimentary rock successions on Baltica. The boundary interval spans the Manndrapselva Mbr of the Stáhpogieddi Fm. and the Lower Mbr of the Breidvika Fm., consisting of several coarsening upward cycles, each less than 100 meters thick, dominated by mudstone and sandstone, and terminated by shallow-marine sandstone. Nigel Banks established the general succession of trace fossils in the 1970's, with additional information added more recently by Duncan McIlroy and members of the Digermulen Early Life Research Group. The second cycle of the Manndrapselva Mbr is late Ediacaran on the presence of the problematicum Harlaniella podolica. Trace fossils in this cycle include Planolites, Torrowangea rosei and, uniquely for the Digermulen succession, the horizontal cork-screw shaped Helicolithus. A report of treptichnids is here revised as vertically meandering trace fossils. The greatest trace fossil width in this sequence is 8 mm, although most are a few mm wide; recorded depth less than 10 mm. Close to the base of the third cycle of the Manndrapselva Mbr Treptichnus pedum and Gyrolithes appear. Harlaniella and the lowest occurrences of T. pedum and Gyrolithes are separated by some 30 metres of a sandstone-dominated interval from which trace fossils have not been recovered to date. Higher in the third cycle three-lobed trace fossils of the “Bure ichnocomplex” are found. Treptichnus pedum, Gyrolithes and trace fossils of the Bure ichnocomplex continue into the Lower Mbr of the Breidvika Fm., with T. pedum and Gyrolithes of larger size than found in the Manndrapselva Mbr. In addition there are Rusophycus and rare Teichichnus. The Treptichnus pedum Zone on the Digermulen Peninsula spans about 100 metres of section. The general validity of global Ediacaran–Cambrian trace fossil-based correlation has stood the test of time. The succession of trace fossils and problematica on the Digermulen Peninsula allows for particularly close comparison with that of the GSSP section on the Burin Peninsula, Newfoundland, as well as Podolia, Ukraine. Important future challenges include better control on the age of the base of the T. pedum Zone, as well as that of the base of the Rusophycus avalonensis Zone, and the identification of possible diachroneities of these zones, where this is not obviously the result of facies unsuited for trace fossil preservation.
|
|
