Age constraint for the Moreno Hill Formation (Zuni Basin) by CA-TIMS and LA-ICP-MS detrital zircon geochronology

Abstract

The “mid-Cretaceous” (~125–80 Ma) was punctuated by major plate-tectonic upheavals resulting in widespread volcanism, mountain-building, eustatic sea-level changes, and climatic shifts that together had a profound impact on terrestrial biotic assemblages. Paleontological evidence suggests terrestrial ecosystems underwent a major restructuring during this interval, yet the pace and pattern are poorly constrained. Current impediments to piecing together the geologic and biological history of the “mid-Cretaceous” include a relative paucity of terrestrial outcrop stemming from this time interval, coupled with a historical understudy of fragmentary strata. In the Western Interior of North America, sedimentary strata of the Turonian–Santonian stages are emerging as key sources of data for refining the timing of ecosystem transformation during the transition from the late-Early to early-Late Cretaceous. In particular, the Moreno Hill Formation (Zuni Basin, New Mexico) is especially important for detailing the timing of the rise of iconic Late Cretaceous vertebrate faunas. This study presents the first systematic geochronological framework for key strata within the Moreno Hill Formation. Based on the double-dating of (U-Pb) detrital zircons, via CA-TIMS and LA-ICP-MS, we interpret two distinct depositional phases of the Moreno Hill Formation (initial deposition after 90.9 Ma (middle Turonian) and subsequent deposition after 88.6 Ma (early Coniacian)), younger than previously postulated based on correlations with marine biostratigraphy. Sediment and the co-occurring youthful subset of zircons are sourced from the southwestern Cordilleran Arc and Mogollon Highlands, which fed into the landward portion of the Gallup Delta (the Moreno Hill Formation) via northeasterly flowing channel complexes. This work greatly strengthens linkages to other early Late Cretaceous strata across the Western Interior.

14th Symposium on Mesozoic Terrestrial Ecosystems and Biota

“…These alternating paleosols indicate that groundwater fluctuated during a regional (southern Colorado Plateau) regression (R1) coincident with the latest Greenhorn Cyclothem which was followed by the New Mexicospecific T2-R2 transgressive-regressive sequence (Molenaar, 1983). Overall regression and base level fall within the lower member following the T2 is corroborated by the transition from relatively more-sulfurous coastal to less-sulfurous fluvial coals and by increasingly bedload-rich multi-story channel complexes (Hoffman, 1994;Cilliers, 2022). Transitioning to the upper member, sedimentary patterns and pedogenic development remain consistent with continued base level fall and slight aridification albeit with continuing groundwater flux.…”

“…The mid-Cretaceous is demarcated by enigmatic yet globally significant tectonic and climatic processes (Huber et al, 2018). Although our understanding of the Cenomanian-Turonian is improving, geological and paleontological data immediately succeeding the Cretaceous Thermal Maximum remains fragmentary Cilliers, 2022). Fortunately, potential insights into the Turonian-Coniacian transition are preserved within the Moreno Hill Formation (MHF) of the Salt Lake Coal Field (SLCF) in west-central New Mexico (McLellan et al, 1983).…”

“…The upper member correlates to the Crevasse Canyon Formation (Dilco Coal Member) and regionally to the lower Wepo and Straight Cliffs (John Henry Member) formations. Ongoing progradation of the Gallup Delta system in response to the Greenhorn Regression likely resulted in continued maturation of the Moreno Hill floodplain and the biological communities therein (Cilliers, 2022). University of Wisconsin-Oshkosh, Harrington Hall.…”

Diverse Magmatic Evolutionary Trends of the Northern Andes Unraveled by Paleocene to Early Eocene Detrital Zircon Geochemistry

“…In CA‐ID‐TIMS damaged regions within zircon crystals that may have lead loss are removed, resulting in highly accurate and precise dates (errors <0.1%) (Black et al., 2004; Crowley et al., 2007; Mattinson, 2005). Combining these two techniques is the most adequate method to identify detrital age populations and to obtain dates that can resolve high‐resolution stratigraphic or magmatic problems (Cilliers et al., 2021; Herriott et al., 2019).…”