Intrabasinal sediment recycling from detrital strontium isotope stratigraphy

Neal C Auchter,Stephen M Hubbard,Benjamin G Daniels,Howie D Scher,Wayne Buckley,Brian W Romans

doi:10.1130/g47594.1

Neal C Auchter, Stephen M Hubbard + Show 4 more

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https://doi.org/10.1130/g47594.1

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Abstract

Abstract Temporary storage of sediment between source and sink can hinder reconstruction of climate and/or tectonic signals from stratigraphy by mixing of sediment tracers with diagnostic geochemical or geochronological signatures. Constraining the occurrence and timing of intrabasinal sediment recycling has been challenging because widely used detrital geo-thermochronology applications do not record shallow burial and subsequent reworking. Here, we apply strontium isotope stratigraphy techniques to recycled marine shell material in slope deposits of the Upper Cretaceous Tres Pasos Formation, Magallanes Basin, Chile. Detrital 87Sr/86Sr ages from 94 samples show that the majority (&gt;85%) of the shells are &gt;1–12 m.y. older than independently constrained depositional ages. We interpret the gap between mineralization age (87Sr/86Sr age) and depositional age of host strata to represent the intrabasinal residence time of sediment storage at the million-year time scale. We also use specimen type to infer relative position of intrabasinal source material along the depositional profile, where oysters represent shallow-water (i.e., proximal) sources and inoceramids represent deeper-water (i.e., distal) sources. The combined use of detrital strontium isotope ages and specimen types from linked depositional segments provides an opportunity to identify and quantify sediment storage and recycling in ancient source-to-sink systems.

Highlights

Detrital mineral analysis is commonly used to infer geomorphic characteristics, tectonic history, and exhumation patterns associated with ancient sediment source areas
14% of detrital SIS (DSIS) ages are within DZ-MDA ranges, whereas the remaining 86% are ∼1–12 m.y. older than the depositional age (Fig. 3)
Samples were selected based on presence of primary shell material and absence of diagenetic alteration, which can impact Strontium isotope stratigraphy (SIS) and DSIS applications (McArthur et al, 1994)

Summary

Introduction

Detrital mineral analysis is commonly used to infer geomorphic characteristics, tectonic history, and exhumation patterns associated with ancient sediment source areas. There remains a lack of knowledge about recycling at time scales over which basin stratigraphy develops (∼105 to 107 yr) because neither sandstone composition nor crystallization or cooling age of detrital minerals record transient storage and remobilization within a sediment routing system. This study introduces detrital strontium isotope stratigraphy as an approach for identifying and measuring intrabasinal sediment residence time.

Results

Conclusion