Document Type

Honors Project

Publication Date



The tectonic evolution of the Chugach-Prince William Terrane (CPW), an accretionary complex along the southern Alaskan margin, has been the subject of much debate. There are two prevailing hypotheses for the location of the CPW at the time of its intrusion by the plutons of the Sanak-Baranof belt, and both require distinctly different source regions for the sediment of the CPW flysch. Therefore, a better understanding of the provenance of these sediments will help constrain the location of the CPW at the time of the deposition of its sediments. This study presents an analysis of new U/Pb detrital zircon, mineralogical and sedimentological data from the Shumagin Formation, which comprises the westernmost section of the CPW terrane. Our results indicate that the Shumagin Formation on Nagai Island has a maximum depositional age of 73-77 Ma and represents the deposition of a large volume of sediment along a basin on a deep submarine fan adjacent to an active volcanic arc. A comparison of our U/Pb age populations with those of correlative units along strike shows a striking similarity in source material along the length of the CPW. This combined mineralogical and U/Pb detrital zircon data constrain the provenance of the Shumagin Formation to a source region south of the present location of the CPW at the time of its intrusion by the Sanak-Baranof belt and are consistent with the terrane’s subsequent northward, coast-parallel translation.

Level of Honors

magna cum laude




Marcia Bjornerud

appendix a final.docx (201 kB)
Appendix: Raw U/Pb Data