New Mexico Geological Society Annual Spring Meeting — Abstracts

Nearly continuous sections of Upper Cretaceous strata outcrop throughout parts of southern New Mexico. Here, Turonian-Campanian strata are defined from base-to-top by: (1) nonmarine fluvial strata of the Tres Hermanos Formation, (2) lower- and upper-offshore strata of the D-Cross Tongue of the Mancos Shale and lower shoreface strata of the Gallup Sandstone, and (3) nonmarine fluvial strata of the lower member and upper Ash Canyon Member of the Crevasse Canyon Formation. Summarized here are new provenance data (U-Pb detrital zircon geochronology and sandstone modal composition) and paleoflow trends from nonmarine strata that outcrop near Carthage and Truth or Consequences (TorC), New Mexico.

The Tres Hermanos Formation is composed primarily of quartz and lithic fragments (volcanic and metamorphic) with minor amounts of feldspar (Q=63%, F=10%, L=27%). Paleoflow trends show east-directed flow (93°) near TorC and a southeast-directed flow (166°) near Carthage. TorC peak detrital zircons ages include 101, 169, 1127, 1417, and 1698 Ma, with the youngest zircon grain at 92.6 Ma and a calculated maximum depositional age (MDA) of 96 Ma. Carthage peak detrital zircon ages include 94, 151, 1080, 1426, 1712 Ma, with the youngest zircon grain at 89.7 Ma and a calculated MDA of 94 Ma.

The lower member of the Crevasse Canyon is composed primarily of quartz and lithic fragments (volcanic and metamorphic) with minor amounts of feldspar (Q=50%, F=9%, L=41%). Paleoflow trends near TorC show an east-directed flow (100°) and peak detrital zircon ages include 98, 168, 1050, 1406, and 1685 Ma, with the youngest zircon grain at 88.9 Ma and a calculated MDA of 98 Ma. Carthage peak detrital zircon ages include 98, 149, 1069, 1117, 1415, and 1706 Ma, with the youngest zircon grain at 88.5 Ma and a calculated MDA of 91 Ma.

The upper Ash Canyon member of the Crevasse Canyon is composed primarily of quartz and lithic fragments (volcanic and metamorphic) with minor amounts of feldspar (Q=48%, F=6%, L=46%). Paleoflow trends at Carthage show a southeast-directed flow (118°). Peak detrital zircon ages from lower part of Ash Canyon Member near TorC include 94, 150, 171, 1419, and 1687 Ma, with the youngest zircon grain at 79.8 Ma and a calculated MDA of 94 Ma. The upper part of the Ash Canyon Member near TorC has peak detrital zircon ages of 79, 90, 166, 1409, and 1678, with the youngest zircon grain at 78.3 Ma and a calculated MDA of 79 Ma. Carthage peak detrital zircon ages include 91, 98, 152, 171, 1110, 1413, and 1674 Ma, with the youngest zircon grain at 86.6 Ma and a calculated MDA of 91 Ma.

Based on trends summarized above, we favor a sediment dispersal model where the Tres Hermanos and Crevasse Canyon Formations were sourced from recycled orogen and arc source areas that were likely located in the west-southwest parts of the Cordillera. Source areas likely included Mesozoic magmatic systems of the southwestern Cordillera as well as Precambrian sources of the Yavapai and Mazatzal, Grenville, and Mogollon Highland provinces of the southwestern United States.