Detrital zircon geochronology of modern river sediment in south-central Alaska: Provenance, magmatic, and tectonic insights into the Mesozoic and Cenozoic development of the southern Alaska convergent margin

Abstract

New and previously published detrital zircon U-Pb ages from sediment in major rivers of south- central Alaska archive several major episodes of magmatism associated with the tectonic growth of this convergent margin. Analysis of detrital zircons from major trunk rivers of the Tanana, Matanuska-Susitna, and Copper River watersheds (N = 40, n = 4870) documents major <250 Ma age populations that are characteristic of the main phases of Mesozoic and Paleogene magmatism in the region as documented from limited U-Pb ages of igneous rocks. Key points from our detrital record include: (1) Major magmatic episodes occurred at 170, 150, 118, 95, 72, 58, and 36 Ma. The overall pattern of these ages suggests that felsic magmatism was episodic with periodicity ranging between ~14 and 32 m.y. with an average of ~22 m.y. (2) Magmatism in south-central Alaska shows similar age trends with both the Coast Mountains batholith and the along-strike Alaska Peninsula forearc basin strata, demonstrating a spatial and temporal relationship of felsic magmatism along the entire northern Cordilleran margin. (3) Topography and zircon fertility appear to influence the presence and/or absence of detrital zircon populations in individual watersheds. Results from this study indicate that regionally integrated detrital zircon populations from modern trunk rivers are faithful recorders of Mesozoic and Paleogene magmatic events along a convergent margin, but there appears to be a lag time for major rivers to record Neogene and ongoing magmatic events.

Local Singularity Spectrum: An Innovative Graphical Approach for Analyzing Detrital Zircon Geochronology Data in Provenance Analysis

“…Similar or comparable age peaks observed in samples from different locations can provide initial indications of potential provenance affinity among these samples. The establishment of stationary provenance connections in support of paleogeography reconstruction, tectonic evolution, and other provenance-related issues is further supported by comparable Hf isotopic data and concurrent magmatic and/or metamorphic activities [7][8][9][10]. The analysis of age spectrum correlation is crucial in examining the similarities and differences among spectra of various samples.…”

Seismic hazard analysis using Deterministic Seismic Hazard Analysis (DSHA) Method: A case study in Southern Malang District, East Java

“…This difference can occur due to differences in the level of rock cohesiveness, density, and rock strength (Karimzadeh, Feizizadeh, & Matsuoka, 2017;Maringue et al, 2022). Paleogene-aged rocks have material that is loose, not solid, and not compact (Fasulo & Ridgway, 2021 Therefore, when exposed to energy from earthquake waves, the material will be easily moved.…”