Stratigraphic Nomenclature
allof ormation rank if they comprised part of an andent nonmarine succession. A comparison with the
eight units of Allen and Williams (1982) is suggested
here, with a change in rank to allomembers. The
entire postglacial valley-fill complex would then
rank as an alloformation.
A proposal for a correlation between allostratigraphic units, the bounding-surface hierarchy, and
sequence concepts is presented in Chap. 13.
A recent study of a stratigraphic succession in
Wyoming was carried out for the specific purpose of
comparing the use of lithostratigraphic, allostratigraphic, and sequence nomenclature for the subdivision and interpretation of an interfingering
marine-nonmarine clastic succcession. The study
was by Martinsen et al. (1993), who discussed the
stratigraphy of the Hanna Basin, an Upper Cretaceous foreland basin. A system of lithostratigraphic
nomenclature was available from earlier work and
provided a complete framework of named units for
descriptive purposes. Allostratigraphic concepts en309
abled the complex of laterally interfingering units to
be related to each other and provided the basis for a
simpler system of named units, but uncertainties
remained regarding the definition of boundaries,
because in places the units are conformable, and no
discernible lithologic changes could be discovered to
enable placement of the boundaries to be completed.
To then compare this allostratigraphic framework
with one constructed using sequence concepts is
perhaps inappropriate, because allostratigraphy is
intended to be purely descriptive, whereas sequence
stratigraphy' is genetic and can lead to very specific
predictions regarding stratigraphic composition
and geometry (Chap. 13). Sequence concepts can be
used to construct a complete stratigraphic fr amework as long as some of the basic elements of the
sequence model can be observed, although in this
case difficulties arose because the rapid subsidence
and the particular tectonic style of the Hanna Basin
made comparisons with standard sequence models
difficult.
allof ormation rank if they comprised part of an andent nonmarine succession. A comparison with the
eight units of Allen and Williams (1982) is suggested
here, with a change in rank to allomembers. The
entire postglacial valley-fill complex would then
rank as an alloformation.
A proposal for a correlation between allostratigraphic units, the bounding-surface hierarchy, and
sequence concepts is presented in Chap. 13.
A recent study of a stratigraphic succession in
Wyoming was carried out for the specific purpose of
comparing the use of lithostratigraphic, allostratigraphic, and sequence nomenclature for the subdivision and interpretation of an interfingering
marine-nonmarine clastic succcession. The study
was by Martinsen et al. (1993), who discussed the
stratigraphy of the Hanna Basin, an Upper Cretaceous foreland basin. A system of lithostratigraphic
nomenclature was available from earlier work and
provided a complete framework of named units for
descriptive purposes. Allostratigraphic concepts en309
abled the complex of laterally interfingering units to
be related to each other and provided the basis for a
simpler system of named units, but uncertainties
remained regarding the definition of boundaries,
because in places the units are conformable, and no
discernible lithologic changes could be discovered to
enable placement of the boundaries to be completed.
To then compare this allostratigraphic framework
with one constructed using sequence concepts is
perhaps inappropriate, because allostratigraphy is
intended to be purely descriptive, whereas sequence
stratigraphy' is genetic and can lead to very specific
predictions regarding stratigraphic composition
and geometry (Chap. 13). Sequence concepts can be
used to construct a complete stratigraphic fr amework as long as some of the basic elements of the
sequence model can be observed, although in this
case difficulties arose because the rapid subsidence
and the particular tectonic style of the Hanna Basin
made comparisons with standard sequence models
difficult.