Abstract
Sedimentology and provenance of the Upper Cretaceous (Cenomanian to Santonian) Frontier Formation, southwest Montana and east-central Idaho
Abstracts with programs - Geological Society of America, Vol.50(6)
Geological Society of America, 2018 annual meeting & exposition
11/2018
DOI: 10.1130/abs/2018AM-321349
Abstract
The Frontier Formation near Lima Peaks and the western Centennial Mountains is characterized as a dominantly non-marine approximately 800-2000m thick foreland basin deposit. Frontier strata in the western Centennial Mountains are situated in an area of structural overlap between the northwest-trending Sevier-style Idaho-Montana fold-and-thrust belt and the northeast-trending Laramide-style Blacktail-Snowcrest uplift. The aim of this study is to integrate the sedimentology with new multi-proxy provenance data to investigate both of these topographically high regions as potential sediment sources during Frontier time. Our approach is to build a dataset of measured stratigraphic sections, sandstone petrographic data, detrital zircon and detrital apatite U-Pb geochronological data, and biostratigraphical data to construct a chronostratigraphic framework in which to interpret the provenance data. Preliminary results from our sedimentological observations support previous interpretations that the Frontier Formation is a fine-grained fluvial system that accumulated in a structurally complex part of the foreland basin. Detrital zircon analyses show a youngest graphical peak age of approximately 87-88.5 Ma, a largest graphical peak age of approximately 94.5-99 Ma and additional minor populations of approximately 157 Ma, approximately 1000-1100 Ma, approximately 1400 Ma, approximately 1620-1680 Ma, approximately 1740-1790 Ma and approximately 2700 Ma. Overall the maximum depositional ages inferred from the youngest graphical peaks are consistent with published ages of 85.81 + or - 0.22 Ma and 86.25 + or - 0.38 Ma from (super 40) Ar/ (super 39) Ar of sanidine found in volcanogenic units of the middle Frontier Formation. Additionally, palynological data from the middle Frontier indicates a depositional age of Coniacian (89.8-86.3 Ma or younger). In contrast, detrital apatite analyses range from approximately 80-220 Ma, with peaks around approximately 82 Ma, approximately 94 Ma, approximately 105 Ma, approximately 115 Ma and approximately 130 Ma. In summary, provenance signatures based on detrital zircon suggest a predominance of Early-Late Cretaceous first-cycle igneous sources and a coeval Coniacian source from the Idaho batholith. The minor older peaks likely represent recycling of the Paleozoic passive margin strata of the fold-and-thrust belt. In comparison, the young nature of detrital apatite populations (<220 Ma) suggests that apatite predominantly records only first-cycle sediment flux from the Cordilleran Arc.
Details
- Title: Subtitle
- Sedimentology and provenance of the Upper Cretaceous (Cenomanian to Santonian) Frontier Formation, southwest Montana and east-central Idaho
- Creators
- Justin A Rosenblume - University of IowaEmily S FinzelKacey L Garber
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.50(6)
- Conference
- Geological Society of America, 2018 annual meeting & exposition
- Publisher
- Geological Society of America (GSA)
- DOI
- 10.1130/abs/2018AM-321349
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, 2018 annual meeting & exposition
- Language
- English
- Date published
- 11/2018
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229963802771
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