HR: 1340h
AN: T33C-1481    [Abstracts]
TI: Sedimentary and structural history of the basal member of the Abiquiu Formation: Implications for Cenozoic landscape evolution of the northern New Mexico
AU: * Huff, P
EM: fatpat3864@aol.com
AF: University of Houston, Geosciences Department, Houston, TX 77204, United States
AU: Murphy, M A
EM: mmurphy@mail.uh.edu
AF: University of Houston, Geosciences Department, Houston, TX 77204, United States
AU: Blankenship, E
EM: geoblue22@yahoo.com
AF: University of Houston, Geosciences Department, Houston, TX 77204, United States
AU: Hicks, R
EM: tatiara@hotmail.com
AF: University of Houston, Geosciences Department, Houston, TX 77204, United States
AB: Structural, stratigraphic, and sedimentalogic data from the the basal member of the Oligocene-lower Miocene Abiquiu Formation provides information on the late Cenozoic deformation history and landscape evolution of north-central New Mexico. The study area lies along the western margin of the Rio Grande rift. The basal member of the Abiquiu Formation lies unconformably on Mesozoic strata and locally the Cenozoic El Rito Formation. RTK GPS mapping of the unconformity shows that it is planar and regionally strikes N70E and dips 17SE. Within the study area the basal member of the Abiquiu Formation is a 125 m thick sequence of interbedded boulder, pebble, cobble conglomerate and coarse-grained sandstone. Bedding ranges from 10 to 50 cm thick and bedforms are planar to slightly undulatory at their base. Clasts within conglomerate beds are matrix supported, but are locally imbricated. Paleoflow measurements from the base of the basal member yield a mean paleoflow direction of 326 degrees. Clasts composition consists of a variety quartzites and foliated granite that are in general subrounded and highly spherical. These bedforms and sedimentary textures suggest that the environment of deposition is sheet flood dominated alluvial fan. Provenance and paleoflow data from the basal member of the Abiquiu Formation indicate that the paleogeography of the western margin of the Rio Grande rift in north-central New Mexico underwent a significant change during the Miocene. At the time of deposition the region presently defining the western margin of the Rio Grande rift was a topographic low and receiving detritus from the south-southeast. Sometime after the Early Miocene, the landscape was inverted, whereby the western margin of the rift was uplifted resulting in southeastward titling of the Abiquiu Formation, while regions to the southeast subsided. Regional southeast tilting of the Abiquiu Formation cannot be readily explained by slip along faults delineating the western margin of the Rio Grande rift. Rather, regional tilting likely results from basin-scale tilting due to slip along faults defining the eastern margin of the Rio Grande rift.
DE: 8015 Local crustal structure
DE: 8110 Continental tectonics: general (0905)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting