Drainage reorganization and Laramide tectonics in north‐central New Mexico and downstream effects in the Gulf of Mexico

Abstract

The El Rito and Galisteo depocenters in north-central New Mexico archive tectonically-driven Paleogene drainage reorganization, the effects of which influenced sedimentation along the northwestern margin of the Gulf of Mexico. Although separated by ~100 km and lacking depositional chronology for the El Rito Formation, the two aforementioned New Mexican depocenters are commonly considered remnants of a single basin with coeval deposition and shared accommodation mechanism. Detrital zircon U-Pb maximum depositional ages indicate that the El Rito and Galisteo formations are not coeval. Moreover, stratigraphic thickness trends and mapping relationships indicate different accommodation mechanisms for the Galisteo and El Rito depocenters; tectonically-induced subsidence versus infilling of incised topography, respectively. The regional unconformity that bounds the base of both the El Rito and Galisteo formations is a correlative surface induced by local tectonic activity and associated drainage reorganization in the early Eocene, and was diachronously buried by northward onlap of fluvial sediments. Detrital zircon distributions in both depocenters indicate increased recycling of Mesozoic strata above the unconformity, but diverge upsection as topographic prominence of local basement-involved uplifts waned. Sediment capture in these depocenters is coeval with deposition in other externally-drained Laramide basins. Further, it corresponds to a period of low Laramide provincederived sediment input and replacement by Appalachian-sourced sediment along the northwestern margin of the Gulf of Mexico during a basin-wide transgression. This illustrates the potential effect that pockets of sediment storage within the catchment of a transcontinental drainage system can have over the sedimentary record in the receiving marine basin. K E Y W O R D S detrital zircon U-Pb, drainage reorganization, Gulf of Mexico, Laramide, stratigraphy 420 | EAGE SMITH eT al.

Detrital zircon age spectra of middle and upper Eocene outcrop belts, U.S. Gulf Coast region

“…We tentatively route these rivers to the central portion of the Texas coastal plain, simply because the along strike changes in 1,800-1,600 Ma age modes imply a source area that was geographically between those for deltas to the north and south (Table 2). This is also consistent with a recent detrital zircon-based analysis, focused on Laramide basins in north-central New Mexico (Smith et al, 2019).…”

“…Several authors have recently integrated this observation into detrital zircon‐based provenance analysis, and we contend that (a) at least some direct sourcing from high‐standing Ouachita foreland basin strata accounts for the anomalous heavy minerals (e.g., Wahl et al., 2016). Moreover, (b) although any rivers that originated in the Appalachian foreland and flowed west would have been integrated into a coeval Mississippi river system (therefore, precluding a direct source‐sink connection between the southern Appalachian orogen and eastern Texas), it seems plausible that some of this material could have been reworked westward along the continental margin during a time of low sediment supply (e.g., Smith et al., 2019).…”

“…In terms of the northernmost possible sediment source to southern Texas (number 3 on Figure 7), analysis of the interior Laramide region in northwestern New Mexico has suggested that rivers draining the southwestern parts of the Colorado magmatic provinces flowed to the east across a break in the Laramide structural front in central New Mexico (Gorham & Ingersoll, 1979; Lawton, 2008; Smith, Lucas, & Elston, 1985; Smith et al., 2019). Rivers also likely originated on the eastern flank of the Laramide province at this latitude and flowed eastward towards the Gulf Coast (Bush, Horton, Murphy, & Stockli, 2016).…”

“…However, by the middle Eocene (or even the late part of the early Eocene), the evidence seems reasonably clear that the cordilleran arc drainage had been disrupted (e.g., Sharman et al., 2017). The stratigraphic evidence for disruption includes the presence of closed basins in the interior Laramide region in the early middle Eocene (e.g., Davis, Mulch, Carroll, Horton, & Chamerlain, 2009; Lawton, 2008; Smith, Carroll, & Singer, 2008), detrital evidence for unroofing in those Laramide basins and local sediment storage (Bush et al., 2016; Carroll, Chetel, & Smith, 2006; Smith et al., 2019), and a decrease in sediment supply to the Gulf Coast in the early middle Eocene (e.g., Galloway et al., 2011). In addition to this evidence, we note that Wilcox Group detrital zircon age spectra from south Texas to the Sabine uplift lack the 1,250–950 Ma age distributions that are found in younger, spatially overlapping Claiborne Group strata, as described above (e.g., Blum et al., 2017; Blum & Pecha, 2014; Craddock & Kylander‐Clark, 2013; Wahl et al., 2016).…”