12 Tectonics, Volcanism, and Sediment Dispersal Within and Proximal to the Rio Grande Rift and Southern Rocky Mountains

This session integrates research on coupled tectonics, volcanism, and sediment dispersal in the Rio Grande Rift and southern Rockies. We examine how extensional faulting controls volcanic processes and reshapes sediment routing from Colorado through Texas.

Monday, 18 May 2026
1:30 PM - 4:30 PM
Alvarado A

Climatic and tectonic controls on 14–10 Ma piedmont progradation in the central Rio Grande rift, New Mexico

Paper number: 12-7
Program: Technical Sessions
Time: 3:35 PM – 3:55 PM

Authors

Abstract

We document and temporally constrain a major phase of piedmont progradation between 14 and 10 Ma in the eastern Española Basin (EEB) and northwestern Albuquerque Basin (NWAB) and evaluate possible paleoclimate and tectonic drivers.  In the EEB, the toe of the eastern piedmont (lithosome A, Tesuque Fm) advanced ~3 km westward between 13.8 and 13.1 Ma, briefly shifted up to 5 km eastward ~13.1–13.0 Ma, and then prograded 7–9 km westward between 13.0 and 10 Ma. Two fluvial systems sourced from the southeastern Colorado Plateau entered the NWAB. Deposits of the northern fluvial unit of the Cerro Conejo Formation (Ncnf) accumulated on a broad south- to southeast-sloping piedmont at 13.5–10 Ma. To the south, a western piedmont facies of the Cerro Conejo Formation (Ncw) prograded >3 km eastward between 13 and 10 Ma and interfingered eastward with Ncnf. The distal piedmont becomes more gravely after 13.1 Ma in the NEB, but in the NWAB notable gravels do not appear until ~10 Ma.

We compare the timing of progradation and coarsening to stratal tilt, accumulation rates, and δ¹⁸O values from authigenic carbonates. Tilt rates are steady in the EB during 14–11 Ma and in the NWAB tilt rates may lessen after 14–13 Ma. In both basins, stratal accumulation rates (not decompacted) are high 15–14 Ma and decrease between 14 and ca. 12 Ma. The majority of the progradation occurred after 13 Ma, coincident with a shift toward higher δ¹⁸O that we interpret reflects increasing summer-dominated precipitation. Tectonic tilting may have aided progradation, but we infer that the main driver (especially post-13 Ma progradation) was strengthened monsoonal circulation that promoted high-intensity runoff events.

For most of the Miocene, remnants of the Chuska Sandstone (Early Oligocene) capped the southeastern Colorado Plateau. The muted expression of the ~13 Ma coarsening event in the NWAB may reflect lower depositional slopes and high permeability in these headwaters, which reduced runoff through increased infiltration. We hypothesize that exhumation of this sandstone exposed less permeable Upper Cretaceous strata, and this increased overland flow and discharge, enhancing stream competency and enabling gravel delivery to the NWAB by ~10 Ma. These results highlight the interplay of climate, tectonics, and substrate permeability in modulating sediment flux within continental rift basins.

 

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410697

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