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1 DATA REPOSITORY ITEM : manuscript: Tectonic history of a Jurassic backarc basin sequence (the Gran Cañon Formation, Cedros Island, Mexico) based on compositional modes of tuffaceous deposits Salvatore Critelli* Dipartimento di Scienze della Terra, Università degli Studi della Calabria, Arcavacata di Rende (CS), Italy Kathleen M. Marsaglia Department of Geological Sciences, California State University, Northridge, California , U.S.A. Cathy J. Busby Department of Geological Sciences, University of California, Santa Barbara, California 93106, U.S.A. * corresponding author; critelli@unical.it kathie.marsaglia@csun.edu cathy@magic.geol.ucsb.edu Data Repository item contain additional material related to this article DATA REPOSITORY of Tables DR1, DR2, DR3, DR4: 1 GSA Data Repository item, table DR1, Field description of samples used for petrographical study and lithofacies subdivision of the Gran Cañon Formation is available on the Web at Requests may also be sent to Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301; editing@geosociety.org. 2 GSA Data Repository item, tables DR2, DR3, DR4, raw data (DR2) and recalculated modal point count data (DR3) for the Gran Cañon Formation, and recalculated average vitric, microlitic, lathwork and felsitic volcanic lithic grains of published volcaniclastic sand(stone) suites (DR4) for which raw data were published or could be obtained from the authors (including our own unpublished raw data), are available on the Web at Requests may also be sent to Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301; editing@geosociety.org.

2 Table 1.- Field description of samples used for petrographical study and lithofacies subdivision of the Gran Canon Formation. SAMPLE STRATIGRAPHIC POSITION FIELD DESCRIPTION EPICLASTIC LITHOFACIES GC57A Section 2, Arroyo Choyal, near base. Coarse-grained sandstone, in a section of thin-bedded fine-grained sandstone and siltstone. GC56A Section 2, Arroyo Choyal, near base. Medium bed of coarse-grained sandstone, interstratified with fine-grained thin-bedded sandstone and siltstone. GC266 Section 2, Arroyo Choyal, 2 m from base. Thick bed of coarse-grained massive sandstone. PRIMARY VOLCANIC LITHOFACIES GC62 South Cedros, in a sheared section. Deformed tuffaceous sandstone, possibly interstratified with pillow basalts but the section is faulted. GC m, Arroyo Gran Canon. Thin-bedded felsic tuff from base of dacite pyroclastic rocks section, "pumice lapilli tuff" of Fig. 7 (Busby-Spera, 1988). GC238b Dacite pyroclastic rocks, Arroyo Gran Canon. Upper part of a 2m thick dacite tuff bed: basal 80cm massive very coarse-grained tuff grades upward in very coarsegrained tuff grades into thin-bedded medium-grained tuff grades upward into very thin-bedded medium-to fine-grained tuff. GC242 Dacite pyroclastic rocks, Arroyo Gran Canon. Dacite tuff breccia, with dacite lithics and abundant pumice. Forms a graded bed (see center column, Fig. 7B of Busby-Spera, 1988). GC261 Section 2, Arroyo Choyal, between lower pillow basalt and T3. Thin-bedded crystal dacite tuff interstratified with thin- to very-thick bedded mafic tuffs. Shards visible in hand sample. GC from base of T4, sect. 2, Arroyo Choyal. 2m thick graded dacite lapilli tuff to tuff, at the top of a 14 m thick section of thin- to medium-bedded, medium-grained to coarse-grained tuffs. Overlain by dacite tuff breccia (i.e. forms part of an upward-coarsening sequence of beds). GC1 section 1, Arroyo Choyal. Dacite tuffs, thin- to medium-bedded, in basal part of T4: moderately well sorted, laminated (subaqueous fallout tuff, fine ash removed during settling through water). GC8b T4 on section 1, Arroyo Choyal. Thin-bedded graded dacite tuff with planar lamination overlaying a 1m thick dacite lithic lapilli crystal tuff. GC15 T4 on section 2, Arroyo Choyal. Dacite lithic tuff. GC40A T3 on sect.1 Arroyo Choyal, directly above pillow basalt. Mafic thin bedded felsic tuff interstratified with felsic thin bedded tuffs. GC48A T4, section 1, Arroyo Choyal. 70 cm thick massive dacite lapilli tuff, interstratified with thin bedded medium-grained crystal tuffs and fine-grained vitric tuffs. GC53U Caps upper pillow basalt, section 2, Arroyo Choyal. upper part of 3 m thick graded mafic lapilli tuff bed; lower part has pumice lumps. LAPILLI TUFF-TUFF BRECCIA LITHOFACIES GC240 Arroyo Gran Canon section directly below basalt horizon. Thin-bedded coarse-grained mafic tuff. GC234b Arroyo Gran Canon section, m 6 m thick graded bed of mafic lapilli tuff and tuff. Lower half is massive and has 40% lithic lapilli with (directly beneath the basalt horizon). inverse-graded base, upper half is massive to indistinctly thin-bedded tuff (sample from upper half). GC52 Section 2, Arroyo Choyal, 1m below lower pillow basalt. Coarse-grained mafic tuff. GC237 Arroyo Gran Canon section, +500m at top of Sample from top of a 1 1/2 m thick graded mafic lapilli tuff to tuff. Lower part massive, upper part 50 m thick bedded tuffs (see sample GC233). thin bedded, laminated coarse-grained to medium-grained tuff. GC233 Arroyo Gran Canon section, +469m. 2 m thick massive mafic tuff, at base of 50 m thick section of massive very thick-bedded mafic tuffs, in turn overlain by tuff breccia. GC219 Arroyo Gran Canon section 8 m thick dacite lithic lapilli tuff breccia, with blocks concentrated near base of bed (sample near the top), gradationally overlain by 2 m of thin bedded crystal tuff. TUFF LITHOFACIES GC44 section 2, Arroyo Choyal, +300m. Mafic coarse-grained tuff. GC20 section 3, Arroyo Choyal, +260m. Basaltic or andesite lithic lapilli tuff with green euhedral feldspar and pumice and scoria. GC19a section 3, Arroyo Choyal, +250m. Graded bed: 3 m thick mafic tuff, 19a near base (coarse-grained base), 19b GC19b near top (medium-grained). Interstratified with fine-grained tuffs. GC36 section 1, Arroyo Choyal, +200m. 2 m thick graded mafic tuff/sandstone: coarse-grained at base, medium-grained at top, massive. Interbedded with thin bedded fine-grained mafic tuffs. GC35 section 1, Arroyo Choyal, +150m. 25 cm-thick sandstone or tuff, well-sorted. GC231b Arroyo Gran Canon section, +131m. 1.5 m thick mafic tuff, graded from massive to very indistinctly medium-bedded to indistinctly thin-bedded near top; coarse-grained tuff at base, very fine-grained tuff at top. Sample 30cm from base of bed. GC230 Arroyo Gran Canon section, +119m. 5 m thick greenish brown graded mafic lapilli tuff: basal 2 m massive lapilli tuff (sample from this), overlain by 1 1/2 m massive tuff, overlain by 1 1/2m indistinctly thin bedded crystal tuff and vitric tuff. GC17 section 3, Arroyo Choyal, +20m. 15 cm-thick graded bed of dacite tuff, in a section of fine-grained very fine-grained mafic tuffs. GC202 Basal part of Arroyo Gran Canon section. Medium bed of coarse-grained basalt or andesite tuff in a section of thin-bedded fine-grained tuffs. GC205a Basal Arroyo Gran Canon section. Upper part of a 2 1/2 m thick doubly-graded sequence of beds: medium bedded lapilli tuffs overlain by thinbedded, graded and laminated crystal tuffs (basaltic or andesitic). Lies in a section of thin bedded fine-grained tuffs.

3 Tab. DR2.- RAW DATA. Categories used for sandstone/tuff samples point-counts and assigned grains in recalculated plots are those of Zuffa (1985, 1987), Critelli & Le Pera (1994), and Critelli & Ingersoll (1995). r.f. = coarse grained rock fragme CE = extrabasinal carbonate grains; CI = intrabasinal carbonate grains; NCI = intrabasinal noncarbonate grains. modal point-counts and assigne Mafic Petrofacies (syneruptive) Felsic Petrofacies (syneruptive) mixed felsic/mafic Petrofacies Assigned grains in Syneruptive Posteruptive recalculated plots Petrographic classes GC240 GC52 GC237 GC233 GC44 GC36 GC35 GC20 GC19b GC19aGC231bGC230 GC202GC205a GC213GC238b GC1 GC8b GC15 GC262 GC261 GC40a GC219 GC242 GC17 GC48a GC53u GC62 GC234b GC57a GC56a GC266 Qm Quartz (single crystal) Qt Qp Polycrystalline quartz Qm Quartz in felsic neovolcanic (neo-v) r. f K K-feldspar (single crystal) F K-feldspar in felsic neo-v r.f P Plagioclase (single crystal) Plagioclase in mafic neo-v r. f Plagioclase in felsic neo-v r. f Micas (single crystals) Micas in felsic neo-v r.f Lvmi Volcanic lithic (VL) with microlitic texture Lvl VL with lathwork texture Lvv Mafic VL with vitric texture (blocky shard) Lvv Mafic VL with vitric texture (scoria fragment) L Lvv Felsic VL with vitric texture (pumice) Lvv Felsic VL with vitric texture (bubble-wall shard) Lvf VL with felsitic granular texture Lvf VL with felsitic seriate texture Extrabasinal Ls Sparitic and Biosparite Limestone Carbonate (CE) Ls Micritic and Biomicrite Limestone : green Hornblende (single crystal) brown Hornblende (single crystal) Dense green Hornblende in felsic neo-v r.f minerals Pyroxene (single crystal) (DM) Pyroxene in mafic neo-v r.f Opaques and other DM (single crystals) Opaques and other DM in mafic neo-v r.f Opaques and other DM in felsic neo-v r.f Intrabasinal Carbonate and CI Bioclast noncarbonate CI + NCI Intraclast, glaucony, and rip-up clast matrix Mx Volcaniclastic (ash) matrix Cm Carbonate cement Calcite replacement on undetermined grain cements Phyllosilicate and clay cements Fe-Oxide cement Siliceous cement and authigenic quartz Zeolite (Heulandite and Laumontite) cement Authigenic albite

4 Table DR3.- Recalculated modal point count data for the Gran Canon Formation sandstone/tuff samples. See Table 2 for explanation of parameters. X = mean; SD = standard deviation. Qm = monocrystalline quartz, F = Feldspars (K + P), Lt = Lithic grains; K = K-feldspar, P = Plagioclase; Qp = Polycrystalline quartz, Lvm = Volcanic and Metavolcanic, Lsm = Sedimentary and Metasedimentary lithic grains; Lm = Metamorphic, Lv = Volcanic, and Ls = Sedimentary lithic grains; Lvv = Vitric volcanic, Lvmi = Microlitic volcanic, Lvl = Lathwork volcanic, Lvf = Felsitic volcanic lithic grains; P/F = Plagioclase/total feldspars. Mean and standard deviation are not recalculated for mixed felsic/mafic syneruptive and posteruptive petrofacies because are few samples. Qm F Lt% Qm K P% Qp Lvm Lsm% Lm Lv Ls % Lvv Lvmi Lvl% Lvf Lvmi Lvl% Lvf Lvv Lvmi+Lvl% Qm F Lt Qm K P Qp Lvm Lsm Lm Lv Ls Lvv Lvmi Lvl Lvf Lvmi Lvl Lvf Lvv Lvmi+Lvl P/F FELSIC Petrofacies (Syneruptive) GC GC238b GC GC8b GC GC GC GC40a GC GC GC X SD ±5 ±13 ±16 ±6 ±4 ±9 ±2 ±2 ±1 ±0 ±0 ±0 ±9 ±8 ±3 ±5 ±4 ±1 ±15 ±14 ±3 ±0.05 MAFIC Petrofacies (Syneruptive) GC GC GC GC GC GC GC GC GC19b GC19a GC231b GC GC GC205a X SD ±2 ±6 ±6 ±11 ±0 ±11 ±1 ±0 ±1 ±0 ±0 ±0 ±12 ±11 ±15 ±4 ±14 ±15 ±3 ±11 ±12 ±0.00 MIXED FELSIC/MAFIC Petrofacies (Syneruptive) GC48a GC53u GC GC234b MIXED FELSIC/MAFIC Petrofacies (Epiclastic Lithofacies, Posteruptive) GC57a GC56a GC266k

5 Table DR4.- Average vitric, microlitic, lathwork and felsitic volcanic lithic grains of selected volcaniclastic sand (stone). Suites Lvv Lvmi Lvl Lvf Lvmi Lvl Lvv Lvf Lvmi References +Lvl Izu-Bonin Arc (Sumisu Rift) Marsaglia (1992) proximal backarc (site 788; 21 samples) X SD distal backarc (sites 790, 791; 47 samples) X SD distal backarc (sites 790 and 791; only 9 more mafic samples) X SD Mariana Backarc Region Packer & Ingersoll (1986) Parece Vela Basin Marsaglia & Devaney (1995) (site 450; 10 samples) X SD Mariana Trough (site 451; 23 samples) X SD site 453 (7 samples) Mariana backarc region sites ) X SD Xtot SDtot Hawaiian Islands Marsaglia (1993) (12 samples: only Hawaii Island) X SD Topanga Group Critelli & Ingersoll (1995) (13 samples; basaltic sandstones) X SD Gulf of California (DSDP LEG 64) X Marsaglia (1991) SD Rio Grande Rift Ingersoll & Cavazza (1991) (Cordito Petrofacies) X SD

Salvatore Critelli* Dipartimento di Scienze della Terra, Università degli Studi della Calabria, Arcavacata di Rende (CS), Italy

Tectonic history of a Jurassic backarc-basin sequence (the Gran Cañon Formation, Cedros Island, Mexico), based on compositional modes of tuffaceous deposits Salvatore Critelli* Dipartimento di Scienze