Print this pageJason Altekruse
University
of California, Geology Department
Davis, California
The Alaska Range suture zone marks the
boundary between the lower Mesozoic continental margin of North America and a
Paleozoic to lower Mesozoic island-arc assemblage. Recently published stratigraphic
and detrital zircon studies of the upper Jurassic and Cretaceous clastic
sedimentary section in the suture zone document a transition in the marine
section from solely island-arc derived sediment in the upper Jurassic to lower
Cretaceous, to a combination of continental and island-arc material in the
middle Cretaceous reflecting proximity of the island-arc to the continental
margin. Additionally, a Late
Cretaceous nonmarine sedimentary section, locally in profound angular
unconformity with the underlying marine section, is interpreted to reflect the
final stage in the development of the suture zone.
The purpose of this study is to constrain the
tectonic and paleogeographic development of south-central Alaska during the
upper Mesozoic. Specifically: (1) make a
preliminary comparison of the heavy mineral assemblages in two Late Cretaceous
nonmarine sections separated by the McKinley Fault, (2) constrain the paleogeographic position of
the island-arc assemblage with respect to the continental margin during the
upper Mesozoic using heavy mineral provenance analysis to compliment existing
detrital zircon data, and (3) use structural analysis to compare the
deformational history of the marine and nonmarine sections, to determine if
deformation of the marine section was widespread before nonmarine
deposition. This combination of
structural and heavy mineral analysis will compliment ongoing studies and
further constrain the history of basin development in southern Alaska and the
tectonic development of south-central Alaska.