Tectonic setting of the southern margin of Laurentia at ~1.29-1.23 Ga.  North-dipping subduction results in a continental margin arc and fore arc basin in Llano area (LU) and a back arc basin in west Texas. [FM - Franklin Mountains; AF - Allamoore Fm. ~ location; CM -Carrizo Mountain rocks ~ location; SDC - Sierra Del Cuervo].  See Mosher (1998).

Tectonic setting of exotic terranes at 1.33-1.27 Ga. Possible position relative to Laurentia is shown, but size of separating ocean is unknown. North-dipping subduction results in formation of a island arc (Coal Creek domain; CCD) and possibly correlative Cerro El Carrizalillo (CEC). This subduction most likely ceased soon after 1275 Ma.  See Mosher (1998).

Cross section across Llano region.

Valley Spring & Packsaddle domain rocks represent a continuum from arc   and arc flank to fore arc and marine environments, respectively.  Valley Spring domain also contains older basement. 

Coal Creek domain island arc forms exotic to Laurentia and shuts off after ~1.27-1.25 Ga.

Collision of southern continent indenter and intervening island arcs with Laurentia.  Llano Deformation Front represents the northern extent of Grenville deformation. See Mosher (1998).

In Llano area (LU), doubling of crust and collision of Coal Creek domain (CCD) arc occurred. 

Rift forms perpendicular to collision margin in Central Basin Platform (CBP). Volcanism and plutonism initiates in far west Texas Franklin Mountains (FM).

Subduction in west Texas continues (not shown) until ~1050 Ma Ga (see Grimes & Copeland, 2004 for timing). Later collision results in thrusting of Carrizo Mountain rocks (CM) over Allamoore Fm.(AF) and synorogenic Hazel Fm. in a transpressional setting.  

Similar collision postulated for Sierra Del Cuervo (SDC) and Cerro El Carrizalillo (CEC).

Cross section through Llano region. Renewed subduction with a southward polarity results in collision of Laurentia, the extinct Coal Creek Domain island arc and a southern continent.