Goals and Proposals

 

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Goals/Proposals
Goals

The goal of the working group is to delineate substages for the Frasnian. Proposals for globally recognized and useful subdivisions will be discussed toward the goal of presentation and vote to the whole of the Subcommission on Devonian Stratigraphy (SDS). The substage boundaries should be recognized by conodonts, additional flora and fauna, as well as related geochemical, magnetic susceptibility, and sequence stratigraphic changes. The criteria for a global standard stratotype section and point (GSSP) should be followed (see Remane et al., 1996 - Episodes). A three-fold substage division was favored in a preliminary SDS vote, but this should not limit consideration of proposals that support other configurations.
1997 and 1998

Four substage proposals have been submitted in 1997 and 1998; a fifth was presented but not formally proposed at the SDS meeting in Morocco.  Three of the proposals recognize the eustatic rise associated with the widespread distribution of Palmatolepis semichatovae as a recognizable mid-upper Frasnian boundary in the lower portion of MN Zone 11 (jamieae or Lower rhenana Zone):

Upper Frasnian substage defined by the eustatic sea level rise associated with widespread Palmatolepis semichatovae near base of MN Zone 11 (Lower rhenana Zone).

Ziegler, W., and Sandberg, C.A., 1997, Proposal of boundaries for a Late Frasnian Substage and for subdivision of the Famennian Stage into three Substages: SDS Newsletter No. 14, p. 11.

Base of Middle Frasnian substage defined by first occurrence of Palmatolepis punctata (base of MN Zone 5 and base of punctata Zone). Base of Upper Frasnian substage defined by the traditional German separation of do I delta, near the base of the Lower Kellwasser Horizon, or utilizing the eustatic rise associated with Palmatolepis semichatovae near base of MN Zone 11.

Becker, R.T., and House, M.R., 1998, Proposals for an international substage subdivision of the Frasnian: SDS Newsletter No. 15, p. 17-22. See for detailed discussion and review of possible stratotypes and reference sections; also see comments by Sandberg, C.A. and Ziegler, W., 1998, Comments on proposed Frasnian and Famennian subdivisions: SDS Newsletter No. 15, p. 43-46.

Base of Upper Frasnian substage defined by the base of Lower gigas (rhenana) Zone.

Rzhonsnitskaya, M.A., 1998, Proposals for an International substages subdivision of the Devonian stages: SDS Newsletter No. 15, p. 53-61. See for correlation table and discussion of reference section.

Two Frasnian substages are recognized in West Siberia, divided near the base of the rhenana Zone.

Yolkin, E.A., 1998, Devonian substages in West Siberia sequences: SDS Newsletter No. 15, p. 62.

The major black shales in New York delineate five intervals within the Frasnian that can be aligned by conodonts with the sequence of global TR cycles. They suggest the possibility of a five-part division of the Frasnian Stage, but it is premature to define such divisions as substages: Interval 1 (MN Zones 1-4): top of Geneseo Shale (TR IIb) at the Givetian/Frasnian boundary to the base of the Middlesex Shale (TR IIc). Interval 2 (MN Zones 5-6): base of Middlesex Shale (TR IIc) to base of Rhinestreet Shale [TR IId(1)]. Interval 3 (MN Zones 6-11): base of Rhinestreet Shale [TR IId(1)] to top of Rhinestreet Shale (Relyea Creek Horizon). Interval 4 (MN Zone 12): top of Rhinestreet Shale to base of Pipe Creek Shale [TR IId(2)]. Interval 5 (MN Zone 13): base of Pipe Creek Shale [TR IId(2)] to Frasnian-Famennian boundary (MN Zone 13) and base of Dunkirk Shale (TR IIe).

Over, D.J., and Kirchgasser, W.T., 1999, Conodonts in the black shale facies of the Appalachian Basin and observations on possible substages of the Frasnian: Abstract Book Errachidia Meeting SDS-IGCP 421, University of Montpellier, p. 36-37.