Orogenic Recycling of Detrital Zircons Characterizes Age Distributions of North American Cordilleran Strata

Abstract

Detrital zircon (DZ) analysis has become the standard tool for source-to-sink sediment routing studies at many spatial and temporal scales. In North American source-to-sink studies, DZ distributions are commonly classified according to the presence/absence and proportions of DZ age groups associated with North American crustal provinces as well as peri-Gondwanan and Cordilleran terranes. Although such a classification scheme is descriptive, these age groups typically do not uniquely identify most recent DZ source areas. Using a compilation of >19,000 individual DZ ages for Mesoproterozoic-Paleogene strata of the northern Rocky Mountains, including 2,053 new analyses from the Paleogene Renova Formation and its equivalents in southwestern Montana, we demonstrate periodic derivation of first-cycle DZ from crystalline sources and widespread recycling of poly-cycle DZ from sedimentary sources over multimillion-year timescales. Results show that (1) DZ age distributions become increasingly complex between Mesoproterozoic and Paleogene time with the introduction of new DZ sources to the study area, but (2) once an age group appears in the northern Rocky Mountains stratigraphy, grains of that age persist up-section. These trends show that most DZ age groups are spatiotemporally ubiquitous and nonunique. We largely attribute this to periodic, tectonically induced recycling of DZ into progressively younger sedimentary systems, rather than prolonged derivation of DZ from crystalline basement sources, a trend that reflects the growth of increasingly complex topography associated with the North American Cordillera.

Evaluating the Shinumo-Sespe drainage connection: Arguments against the “old” (70–17 Ma) Grand Canyon models for Colorado Plateau drainage evolution

“…In addition, whereas Sespe sample 14LS11 is broadly similar to Morrison samples CP13 and CP21 with respect to pre-Mesozoic age distributions (Fig. 14), the association of the Grenville, Picuris, and Yavapai-Mazatzal-age zircon is not particularly diagnostic (e.g., Gehrels and Pecha, 2014;Schwartz et al, 2019). The 1.2 Ga peak in sample 14LS11, based on only 39 total analyses for the entire sample, is not clearly diagnostic of the Morrison Formation.…”

“…The 1.2 Ga peak in sample 14LS11, based on only 39 total analyses for the entire sample, is not clearly diagnostic of the Morrison Formation. Most importantly, sample 14LS11 lacks the high percentage of Mesozoic arc-derived zircon that characterizes the Westwater Canyon Member of the Morrison Formation and other potential Triassic-Jurassic sources (Schwartz et al, 2019). The high Mismatch value of 0.59 between clast 14LS11 and the Morrison Formation ( Fig.…”

Comparison of Detrital Zircon U-Pb and Muscovite 40Ar/39Ar Ages in the Yangtze Sediment: Implications for Provenance Studies

“…The following four approaches have been used to identify zircon reworking: (1) Direct field observation (e.g., appearance of sandstone gravels) [35]. (2) Time-transgressive similarities in detrital zircon age distribution, especially in old age populations [54]. (3) Supplementary information from other detrital minerals (e.g., apatite fission track ages [55]).…”

Determining the source of placer gold in the Anaconda metamorphic core complex supradetachment basin using detrital zircon U-Pb geochronology, western Montana, USA

“…Because none of the potential sources input into the unmixing model were collected directly from the hypothesized source area, we are assuming that samples obtained from other localities have DZ ages that are representative of local units, thus not drastically affecting the modeling results. It has been documented that regional DZ signatures for some of the units in the western U.S. are spatially variable (Schwartz et al, 2019); therefore, sampling potential source inputs from the hypothesized source area itself would improve confidence in the unmixing modeling results. However, even if this were done, the top-down modeling approach must still make a priori assumptions about the potential sources and assume that the sink sample is a pure mixture.…”

“…Formed primarily in felsic igneous rocks, zircon is a heavy and resistant mineral that does not commonly break down when weathered into sedimentary systems; as a result, zircons can be recycled multiple times and be most recently sourced from strata that do not represent their initial depositional unit. It is for this reason that many detrital zircons may give insight into an original source, but not necessarily a proximal one (e.g., Thomas, 2011;Schwartz et al, 2019). Conversely, the weathering of metamorphic and igneous rocks can provide first-cycle grains that can allow direct interpretation of provenance.…”