Koning et al., 2008 – New Mexico Geological Society, 2008 Spring Meeting: New Mexico
Geology, vol. 30, no. 2, p. 53-54.
STRUCTURAL EVOLUTION OF THE EASTERN ESPAÑOLA BASIN, RIO GRANDE
RIFT, NORTH-CENTRAL NEW MEXICO
KONING, Daniel J.1, CONNELL, Sean D.2, SLATE, Janet3, WAN, Elmira4, FERGUSON, John
F. 5, GRAUCH, V.J.S.6, WOLDEGABRIEL, Giday7, PETERS, Lisa1, MCINTOSH, William C.1,
DUNBAR1, Nelia, BROXTON, D. 7, and BALDRIDGE, W. Scott 7
1N.M.
Bureau of Geology, N.M. Tech, 801 Leroy Place, Socorro, NM 87801; dkoning@nmt.edu
Mexico Bureau of Geology, 2808 Central Ave. SE Albuquerque, NM 87106
3 U.S. Geological Survey, P.O. Box 25046, Federal Center, M.S. 913, Lakewood, CO 80225
4 U.S. Geological Survey, 345 Middlefield Road, MS 975, Menlo Park, CA 94025
5 Program in Geosciences, University of Texas at Dallas, P.O. Box 30688, Richardson, TX
75083-0688
6 U. S. Geological Survey, Box 25046, Federal Center, MS 964, Denver, CO 80225-0046
7 Earth and Environmental Sciences Division, P.O. Box 1663, Los Alamos National Laboratory,
Los Alamos, NM, 87545
2 New
We interpret the timing of basin tilting as well as deformation along specific structures in the eastern
Española Basin (EEB). The EEB has a half-graben geometry north of Santa Fe, with beds generally tilted
2-10° W towards a central fault system (CFS). The CFS includes the northeast-striking Embudo fault
system and the Santa Clara fault (SCF) to the north, collectively acting as a rift transfer structure, and the
north-striking, east-down Pajarito fault (PF) to the south. Between the PF and SCF is a 6 km-long zone
consisting of several west-down faults. A series of aligned faults and folds comprise two major northstriking structures east of the CFS. Santa Fe Group basin-fill attains a general thickness of 1-3 km in the
EEB. However, basin-fill thickens to 3-4 km in structural lows related to localized subsidence
immediately adjacent to three faults of the CFS. An unconformity recognized north of Santa Fe is
bracketed between 25-30 Ma.
Stratal tilt data from relatively unfaulted areas indicate an episode of high-tilt rates between 16-10
Ma. Significant deformation continued along the aforementioned two major structures east of the CFS in
the late Miocene-Pliocene. Earlier tilting along these structures is suggested by seismic reflection data and
by angular relations across the 25-30 Ma unconformity (at least locally). Pronounced subsidence occurred
in the structural lows adjacent to the PF and SCF in the late Miocene-Pliocene.
We interpret the timing of vertical displacement along the PF and SCF by comparing thickness
changes and vertical offsets of faulted stratigraphic intervals in the Santa Fe Group. These indicate high
throw rates along the SCF and PF, and faults branching off of these structures, between 13-10 Ma.
Approximately 430-500 m of stratigraphic separation of post-10 Ma Chamita Formation strata and lesser
vertical offset of the Pliocene-age Puyé Formation indicates that significant vertical motion along the SCF
occurred after 10 Ma.
We infer that lateral motion along the SCF commenced by 9-12 Ma and peaked at 6-4 Ma using the
Chamita syncline, which we assume is related to transpression created by the right-step between the EF
and SC. Cross-sections suggest thickness changes across the Chamita syncline for post-12 Ma strata. A
pronounced angular unconformity on the north limb indicates strong folding at 6-4 Ma.