Date File Created Name of Creator 4/21/2007 Kelley Stair GeoRef Data 2004-026604 TI "Late Cretaceous cooling of the east-central Peninsular Ranges Batholith (33 degrees N); relationship to La Posta Pluton emplacement, Laramide shallow subduction, and forearc sedimentation." AU Grove-Marty; Lovera-Oscar; Harrison-Mark AF "University of California at Los Angeles, Department of Earth and Space Sciences, Los Angeles, CA, United States" BK In: Tectonic evolution of northwestern Mexico and the Southwestern USA. BA Johnson-Scott-E (editor); Paterson-Scott-R (editor); Fletcher-John-M (editor); Girty-Gary-H (editor); Kimbrough-David-L (editor); Martin-Barajas-Arturo (editor) SO Special Paper - Geological Society of America. 374; Pages 355-379. 2003. PB "Geological Society of America (GSA). Boulder, CO, United States. 2003." CP United-States PY 2003 LA English AB "Biotite and K-feldspar (super 40) Ar/ (super 39) Ar systems from the east-central Peninsular Ranges batholith near 33 degrees N were affected by two distinct phases of Late Cretaceous rapid cooling. The 85-Ma biotite K-Ar isochron separates comparatively shallow rocks in the southwest that record earlier cooling (91-86 Ma) from deeper rocks in the northeast that record later cooling (78-68 Ma). Samples close to 85 Ma isochron record both episodes of rapid cooling as well as slower cooling between 86 and 78 Ma. Although the 85 Ma isochron also coincides with a steep (1-2 m.y./km) K-Ar age gradient, only localized faulting has been detected along it. We attribute 91-86 Ma cooling to denudation related to emplacement of the voluminous suite of 96+ or -3 Ma La Posta plutons. In contrast, we link cooling after 78 Ma to Laramide shallow subduction beneath the Peninsular Ranges batholith. Our numerical simulations indicate that the latter cooling phase can be explained by either pure erosional denudation or by subduction refrigeration beginning at 80 Ma. In the latter case, erosional denudation occurs during steady-state shallow subduction. While final erosion depths predicted by the two models differ significantly (as much as 20 km for pure erosional denudation but only 11 km for subduction refrigeration followed by erosion), both are within the range indicated by independent thermobarometry of the eastern batholith. Based upon the similarity of independently determined denudation histories from Peninsular Ranges batholith basement rocks and forearc sediments that onlap the northern Peninsular Ranges batholith, we conclude that erosional denudation was probably the most important process between 78 and 68 Ma. We speculate that removal of lower crust and lithospheric mantle beneath the east-central Peninsular Ranges batholith during Laramide shallow subduction triggered erosional denudation and localized thrusting until the density balance between the crust and mantle was restored in latest Cretaceous-early Tertiary time." DE absolute-age; Ar-Ar; Baja-California; basins-; batholiths-; California-; Cenozoic-; chemical-composition; cooling-; Cretaceous-; dates-; deformation-; denudation-; diorites-; emplacement-; erosion-; faults-; fore-arc-basins; geochemistry-; igneous-rocks; intrusions-; isotope-ratios; La-Posta-Pluton; Laramide-Orogeny; Little-Blair-Valley; magmas-; Mason-Valley; melts-; Mesozoic-; metamorphic-rocks; Mexico-; mineral-assemblages; mineral-composition; North-America; paleoenvironment-; Peninsular-Ranges; Peninsular-Ranges-Batholith; petrology-; plate-tectonics; plutonic-rocks; sedimentation-; stratigraphic-units; subduction-; tectonics-; Tertiary-; tonalite-; United-States; uplifts-; Upper-Cretaceous; Vallecito-Valley CC 05A-Igneous-and-metamorphic-petrology; 18-Solid-earth-geophysics DT Serial BL Analytic MC LAT: N323000; N331500; LONG: W1160000; W1170000. NN Includes appendices. IL "Refs: 139; illus. incl. 3 tables, geol. sketch maps." RF "GeoRef, Copyright 2004, American Geological Institute." IS 0072-1077 IB 0-8137-2374-4 CO GSAPAZ AN 2004-026604 UD 200408 Sample Data Item LatDD LongDD Loc_prec AGE AGE AGE AGE SAMPLE_COMMENT Rock_CLASS ROCK_TYPE MATERIAL STATE Units DD DD Ma Ma Ma Ma Method 1 1 1 2 3 4 5 409-B 32.99276667 -116.4226667 0.01 78.6 Gar-bio tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur 1110-1 33.03993333 -116.4071 0.01 82.6 76.1 Granite pegmatite Granite Plutonic WHOLE ROCK Baja California Sur AC 32.9316 -116.2741667 0.01 76.6 74.9 La Posta tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur BM 33.21501667 -116.70795 0.01 86.3 87.4 Ranchita tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur BS 32.63985 -116.2297667 0.01 87.1 La Posts tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur BW-2 32.83703333 -116.2460833 0.01 75.1 La Posts tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur CAR 32.63246667 -116.1173 0.01 81 La Posta tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur CM-1 32.78776667 -116.0205167 0.01 72.1 Granodiorite Granodiorite Plutonic WHOLE ROCK Baja California Sur CP-175 32.9568 -116.5065 0.01 100.1 84.8 80.8 Gd. of Pine Valley Granodiorite Plutonic WHOLE ROCK Baja California Sur CP-128 32.972 -116.5759 0.01 101.1 91.9 92.7 Gd. of Chiquita Peak Granodiorite Plutonic WHOLE ROCK Baja California Sur CS 32.94001667 -116.5646667 0.01 91.9 92.9 Gd. of Chiquita Peak Granodiorite Plutonic WHOLE ROCK Baja California Sur CV 33.21148333 -116.4432 0.01 79.6 75.2 Ranchita tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur DIA 32.70483333 -116.3663833 0.01 90.7 La Posts tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur DSC 32.85203333 -116.5937 0.01 91.1 Granodiorite Granodiorite Plutonic WHOLE ROCK Baja California Sur EM 32.90446667 -116.5690833 0.01 91.9 Granodiorite Granodiorite Plutonic WHOLE ROCK Baja California Sur EQ 33.01378333 -116.3911167 0.01 104.6 78.3 Granite Mountain tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur EV 33.0888 -116.4983833 0.01 101.9 84 Granite Mountain tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur FCM 33.0192 -116.0976333 0.01 78.4 76.4 La Posta TTG tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur GM 33.05101667 -116.4797333 0.01 101.3 82.7 81.2 Granite Mountain tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur IKPG 32.68856667 -116.064 0.01 77.6 La Posts tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur IRR 32.64913333 -116.1102667 0.01 78.1 La Posta tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur JU 33.01841667 -116.5282333 0.01 103.9 84.3 78 Granite Mountain tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur JUCH 33.07045 -116.5438833 0.01 89.4 91.5 Granodiorite Granodiorite Plutonic WHOLE ROCK Baja California Sur KCR 32.7212 -116.4719167 0.01 91.8 La Posta tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur KP 32.9334 -116.4823167 0.01 91.6 Harper Creek gneiss Gneiss Metamorphic WHOLE ROCK Baja California Sur LOS 32.67695 -116.3308667 0.01 89.5 La Posta tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur _BV-2B 33.02535 -116.4327333 0.01 84.6 75.4 Granite pegmatite Granite Plutonic WHOLE ROCK Baja California Sur LP-80 32.72436667 -116.4257333 0.01 90.3 La Posts tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur LPRR 32.64476667 -116.4246833 0.01 92.5 La Posta tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur MMVT 33.07153333 -116.5409167 0.01 79.1 Granite Mtn. tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur MP-17 32.8738 -116.41275 0.01 108.8 90.2 85.7 Las Blancas tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur MP 32.97623333 -116.4157833 0.01 80.7 76.5 La Posts tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur MSR 32.67041667 -116.1058667 0.01 82.5 79.1 La Posta tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur MVY 32.70976667 -116.3843833 0.01 91.2 La Posts tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur PV 32.8133 -116.5107333 0.01 89.9 91.1 Gd. of Pine Valley Granodiorite Plutonic WHOLE ROCK Baja California Sur HE 33.09913333 -116.59565 0.01 88.9 Cuyamaca Res. gd. Granodiorite Plutonic WHOLE ROCK Baja California Sur RG 32.97203333 -116.5159333 0.01 86.4 Rattlesnake Gr. Granite Plutonic WHOLE ROCK Baja California Sur SFH 33.21803333 -116.5778833 0.01 94.1 89.4 85.7 Ranchita tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur SP 33.17791667 -116.1125333 0.01 76.7 75.3 La Posta TTG tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur SY 33.09825 -116.6641667 0.01 98.2 90.8 91.9 granodiorite Granodiorite Plutonic WHOLE ROCK Baja California Sur TO 33.13563333 -116.3780167 0.01 79.4 78.9 La Posta TTG tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur TS 33.20923333 -116.6041833 0.01 87.3 84.3 Ranchita tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur WC 32.66308333 -116.2402167 0.01 83.7 La Posta tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur WYN 33.0945 -116.63085 0.01 90.3 granodiorite Granodiorite Plutonic WHOLE ROCK Baja California Sur YS 33.00196667 -116.3856833 0.01 78.9 74.8 La Posta tonalite Tonalite Plutonic WHOLE ROCK Baja California Sur Method Data 1 SCAN 2004-026604 2 AR-AR:HORNBLENDE 2004-026604 3 AR-AR:MUSCOVITE 2004-026604 4 AR-AR:BIOTITE 2004-026604 5 AR-AR:KF 2004-026604