Middle Jurassic Topawa Group, Baboquivari Mountains, south-central Arizona: Volcanic and sedimentary record of deep basins within the Jurassic magmatic arc

Abstract

Among supracrustal sequences of the Jurassic magmatic arc of the southwestern Cordillera, the Middle Jurassic Topawa Group, Baboquivari Mountains, south-central Arizona, is remarkable for its lithologic diversity and substantial stratigraphic thickness, ≈8 km. The Topawa Group comprises four units (in order of decreasing age): (1) Ali Molina Formation-largely pyroclastic rhyolite with interlayered eolian and fl uvial arenite, and overlying conglomerate and sandstone; (2) Pitoikam Formation-conglomerate, sedimentary breccia, and sandstone overlain by interbedded siltstone and sandstone; (3) Mulberry Wash Formation-rhyolite lava fl ows, fl ow breccias, and mass-fl ow breccias, with intercalated intraformational conglomerate, sedimentary breccia, and sandstone, plus sparse within-plate alkali basalt and comendite in the upper part; and (4) Tinaja Spring Porphyry-intrusive rhyolite. The Mulberry Wash alkali basalt and comendite are genetically unrelated to the dominant calcalkaline rhyolite. U-Pb isotopic analyses of zircon from volcanic and intrusive rocks indicate the Topawa Group, despite its considerable thickness, represents only several million years of Middle Jurassic time, between approximately 170 and 165 Ma.

Stratigraphy and age of Upper Jurassic strata in north-central Sonora, Mexico: Southwestern Laurentian record of crustal extension and tectonic transition

“…Rocks of the Late Triassic to Middle Jurassic magmatic arc consist dominantly of calc-alkaline to alkaline granitoids and rhyolitic to dacitic ash fl ow tuffs and fl ows locally interbedded with quartz arenite and sedimentary strata with abundant volcanic clasts (Plate 1; May and Haxel, 1980;Hardy, 1981;Haxel et al, 1985;Segerstrom, 1987;Tosdal et al, 1989;Nourse et al, 1994;Rodríguez-Torres et al, 2003;González-León et al, 2005;Haxel et al, 2005;Leggett, 2009). Interstratifi ed eolian and shallow-marine quartz arenite indicate that the Middle Jurassic arc was low standing and occupied a graben depression which acted as a trap for quartz-rich sand transported southwest from the Late Triassic-Middle Jurassic erg complex of the Colorado Plateau (Bilodeau and Keith, 1986;Busby-Spera, 1988).…”

Geochemical and isotopic study of Mesozoic magmatism in the Sonobari Complex, western Mexico: Implications for the tectonic evolution of southwestern North America

“…Therefore, Triassic rocks in the area are interpreted as the southward continuation of the Permo-Triassic magmatic belt occurring from southwestern USA (e.g., Barth et al, 1990Barth et al, , 1997Barth and Wooden, 2006;Miller et al, 1995), eastern Peninsular Ranges batholith (Kimbrough et al, 2015;Schmidt et al, 2014), northern Sonora (Arvizu et al, 2009;Arvizu and Iriondo, 2015), eastern and southern Mexico (Torres et al, 1999;Weber et al, 2007;Ducea et al, 2004), and perhaps extending to South America (e.g., Cardona et al, 2010;Maksaev et al, 2014). Jurassic rocks also occur along a continental magmatic arc extending from southwestern USA through the Mojave and Sonora Deserts (Busby-Spera et al, 1990;Barth et al, 2017), northern Sonora (Anderson et al, 2005;Haxel et al, 2005), southern Sonora and northern Sinaloa (this work), central Sinaloa (Cuéllar-Cárdenas et al, 2012), and Maria Madre Island (Pompa-Mera et al, 2013). These rocks are also coeval with rocks in El Arco, Baja California, although the rocks from this region have a geochemical signature indicating an island arc setting (Weber and López-Martínez, 2006).…”

Extensional and Transtensional Continental ARC Basins: Case Studies from the Southwestern United States

“…This indicates that they are deeply buried beneath the arc graben depression. A recent paper by Haxel et al (2005) emphasizes the importance of deep basins within the Jurassic magmatic arc of southern Arizona. Silicic calderas and high-level silicic intrusions are abundant, as is typical of extensional arcs in both continental and oceanic settings (see references in Busby, 2004).…”

“…Subsidence in the extensional arc was uniformly fast and continuous along syndepositional normal faults (Busby-Spera, 1988;Busby-Spera et al, 1990;Riggs and Busby-Spera, 1990;Riggs et al, 1993;Haxel et al, 2005). Shallow marine and deep marine deposits dominated in the north (Figure 19.1A), where the arc was built across thinned continental crust and transitional crust, while nonmarine deposits dominated in the south, where the arc was built upon the craton.…”