Geologic Map of the Casa Grande 30’ x 60’ Quadrangle, west-central Arizona
| dc.contributor.author | Pearthree, Philip A. | |
| dc.contributor.author | Johnson, Bradford J. | |
| dc.contributor.author | Richard, S. M. | |
| dc.contributor.author | Spencer, J. E. | |
| dc.contributor.author | Cook, Joseph P. | |
| dc.date.accessioned | 2024-02-13T15:01:14Z | |
| dc.date.available | 2024-02-13T15:01:14Z | |
| dc.date.issued | 2024-02 | |
| dc.identifier.citation | Pearthree, P. A., Johnson, B. J., Richard, S. M., Spencer, J. E., Cook, J. P., 2024, Geologic Map of the Casa Grande 30’ x 60’ Quadrangle, west-central Arizona, DGM-224, map scale 1:100,000 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10150/670960 | |
| dc.description | The Casa Grande 30' x 60' quadrangle is located between Tucson and Phoenix in Pinal County and northernmost Pima County, southern Arizona. The geomorphology of the area is dominated by the Santa Cruz River and several large tributaries whose courses traverse broad, low-relief valley floors, adjacent broad, gently sloping piedmonts, and generally narrow, northerly elongate mountain ranges. All or parts of at least 10 mountain ranges with diverse geology are covered by this map, but surficial deposits of various types cover about 3/4 of the map area. The Santa Cruz River crosses from the south-central edge to the northwest corner of the map area, passing between the Samaniego Hills and Picacho Peak in the south and exiting west of the Sacaton Mountains. Santa Rosa Wash and its tributaries in the southwest part of the map flow northward to the river. The eastern 1/3 of the map is primarily bedrock of the Tortolita Mountains and Ninetysix Hills and broad, westward-sloping piedmonts covered primarily with variably dissected Pleistocene alluvial fan deposits and lesser amounts of Holocene deposits along or near modern washes. Valley floor deposits associated with regional drainages dominate the western 2/3 of the map. Bedrock mountains have relatively small footprints; their adjacent alluvial piedmonts are covered primarily by late Pleistocene and Holocene tributary deposits and are only locally dissected, typically near the mountain ranges. Generally fine-grained Holocene deposits are widespread on the broad valley floors, but slightly higher late to middle Pleistocene relict basin floor deposits are also laterally extensive. Surficial geologic units range from Holocene stream channel and floodplain deposits along the Santa Cruz River and its larger tributaries and channel, floodplain, and alluvial fan deposits throughout the piedmonts, to remnant early Pleistocene alluvial fan deposits capping very well-rounded Neogene basin fill in a few locations near mountain fronts. Channel deposits and terraces are relatively narrow in the proximal piedmont where incised into higher-standing older alluvium. These deposits are much more laterally extensive in the lower relief mid- and distal-piedmont. Carbonate and clay accumulation in Holocene piedmont deposits is modest to minimal. Late and middle Pleistocene alluvial fan and terrace deposits typically have desert pavement, rock varnish, argillic horizons, and soil carbonate accumulation. Some relict early Pleistocene deposits are littered with carbonate fragments from an eroding petrocalcic horizon. Basin fill alluvium is exposed in deeply dissected, very well-rounded hills in the proximal piedmont. Some of these deposits are capped by early to middle Pleistocene alluvium along the ridge crest. Bedrock geology includes rocks ranging in age from Paleoproterozoic to early Miocene. The Paleoproterozoic Pinal Schist, along with Mesoproterozoic plutonic rocks that intrude it, are exposed in ranges throughout the area. Sedimentary rocks of Mesoproterozoic and Paleozoic age overlie these crystalline basement rocks in the Slate Mountains, Tat Momoli Mountains, and Vaiva Hills. Cretaceous to mid-Cenozoic intrusive rocks crop out in the Tortolita Mountains, Suizo Mountains, Durham Hills, Desert Peak, Picacho Mountains, and Sacaton Mountains. Late Oligocene to early Miocene basaltic to trachtic lava flows and clastic sedimentary rocks are exposed north of the Tortolita Mountains and in the Samaniego Hills, Picacho Peak, Sawtooth Mountains, Tat Momoli Mountains, and Vaiva Hills. Late Cretaceous to Oligocene plutons and their country rocks in the eastern part of the map occupy the northwestern part of the Catalina-Rincon metamorphic core complex (Davis, 1980; Dickinson, 1991). They form culminations that are small in comparison with the major exposures of the core complex in the Santa Catalina and Rincon Mountains, southeast of the map area. These crystalline rocks are variably foliated and lineated, ranging from massive to gneissic to mylonitic. Mylonitic foliation and lineation are developed in the structurally highest rocks, and asymmetric shear fabrics are predominantly indicative of top-to-WSW shearing (Spencer et al., 2002; Ferguson et al., 2002; Richard et al., 1999, 2002). The crystalline rocks of the metamorphic core complex lie in the footwalls of detachment faults that are associated with the Catalina detachment (e.g., Dickinson, 1991) and along which they were exhumed in the late Oligocene to early Miocene (Spencer et al., 2022). In this map area the detachment system is represented by the Guild Wash, Suizo, and Picacho Peak detachments and subsidiary low-angle normal faults. Late Oligocene to early Miocene volcanic and sedimentary rocks are in the hanging wall of the detachment system. Proterozoic rocks occupy structural positions in both the footwall and the hanging wall. | en_US |
| dc.language.iso | en | en_US |
| dc.publisher | Arizona Geological Survey (Tucson, AZ) | en_US |
| dc.relation.ispartofseries | DGM-224 | en_US |
| dc.relation.url | https://library.azgs.arizona.edu/ | en_US |
| dc.rights | Arizona Geological Survey. All rights reserved. | en_US |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en_US |
| dc.subject | Casa Grande | en_US |
| dc.subject | geologic map | en_US |
| dc.subject | Arizona | en_US |
| dc.title | Geologic Map of the Casa Grande 30’ x 60’ Quadrangle, west-central Arizona | en_US |
| csdgm.bounding.west | -112 | en_US |
| csdgm.bounding.east | -111 | en_US |
| csdgm.bounding.north | 33 | en_US |
| csdgm.bounding.south | 32.5 | en_US |
| dc.description.collectioninformation | Documents in the AZGS Documents Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu. | en_US |
| refterms.dateFOA | 2024-02-13T15:01:17Z |
