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Arizona Geological Survey Digital Geologic Map DGM-48 Geologic map of the Saint David 7 1/2' Quadrangle Qys Qy2 Qy1 QTsa QTcr Qi3 Qys Qys Qys Qi3 Qi2 Qi2 Qi1 Qi1 Qi3 Qy1 Qi1 Qy1 d Qy2 Qi2 Qi3 Qi3 Qi3 Qy1 Qy1 Qy1 Qi2 QTsd Qi3 Qi2 Qi2 Qy2 Qi2 Qi3 Qi3 Qi1 Qi1 Qi1 QTsr Qi2r Qi1r Tsp Qy3r Qy3r QTsd Qi2 Qi1 Qi2 Qi1r Qi2 Qys QTsr Qi2 Qi2 Qy2 QTsd Qi3 Qy2 Qy1 Qy1 Qy3 Qy2 Qy1 Qy2 Qy2 Qy2 Qy2 Qy2 Qy1 Qy1 Qy2 Qi3 Qy1 Qy2 Qi2 Qi2 Qy1 Qy1 Qy2 Qi3 Qi3 Qy2 Qys QTsa Qys QTsd Tss Qi1 Qy3 Qi3 Qy1 Qy2 Qi3 Qy1 Qy1 Qi3 Qsf Qi2 Qys Qi2 Qi2 QTsd Qi2 Qi1 Qi1 Qy2 Qy2 Qy2 Qys Qi1 Qy1 Qi2 Qy1 Qi2 Qy1 Qi3 QTsd Qi3 Qy2 Qi1 Qy2 Qys Qys Qy2 Qy2 Qy2 Qy2 Qy2 Qy1 Qy1 Qy1 Qy1 QTsd Qys Qy1 Tsp QTsd Qi2 Qys Qy1 Qi2 Qy1 Qi2 Qi2 Qy1 Qi3 Qi3 QTsa Qy1 Qy1 Qy1 Qy1 Qy1 Qi2 Qy1 Qys Tsp QTsd Tsp Tsp QTsa Qsf Qi2 Qi2 QTsd Qi3 Qi2 Qi2 Qi1 Tsp Tsp QTsd QTsd Tsp Tsp QTsr Qi2 Qy2 Qy2 Qi2 Qy1 Qy2 Qy1 Qy1 Qy1 Qy1 Qy1 Qi3 Qy1 Qi3 Qi2 Qi2 Qi2 Qi1 Qi2 Qi2 Qy3r Qy3r Qy3r Qi2 Qi1 Qy1 Qi1 Qy3r Qy1 Qi2 Qi2 Qi2 Qi2 Qi2 Qi3 Qi3 Qsf Qsf Qi1 Qy2 Qy1 Qi3 Qi2 QTsd Qi1 Qi2 Qi3 Qi3 Qi2 Qy2 Qi2 Qi3 QTsa QTsa Qy1 Qy1 d QTsa Qi3 Qsf Qsf Qi1 Qi1 Qi1 Qi1 Qi2 Qi3 Qi3 QTsa Qy1 QTsd Qi3 Qi3 Qi2 Qi2 Qi2 Qi2 Qy1 Qi2 Qi2 Qi2 Qi2 QTsl Qi1r Qy2 QTsa Qi2 Qi2 Qy2 Qys Tsp Qy1 Qy1 Qy1 QTsd Qi2 Qy2 QTsd Qy2 Qy1 QTsd Qi2 QTsd QTsr Qi2 Qi3 Qy1 Qi3 Qi3 Qy1 QTsd Qi3 Qi2r QTsd Tsp QTsd Qy2 Qys QTsd Qys Qys QTsc Qy1 QTsa Qys Tsp QTsr Qy2 Qy1 Qy1 Qy1 Qy1 Qy1 Qy3r Qy2r Qi3r Qy3r d Qi2 Qsf Qi2 QTsa Qys Qy2 Qys Qy2r QTsd Qi2 Qy1 Qi3 Qsf Qi2 Qy1 Qi1 Qsf Qi3 Qi2 Qys Qy1 Qy1 Qy2 Qys Qi2 Qy1 Qys Qy2 Qys Qy2 QTsd Qy2 Qy1 QTsd Qys Qy2 Qy2r Qy3r Qy3r Qy2r Qi2 Qy1 Qy3 Qy1 Qyc Qy3 Qi2 Qyaf Qyaf Qyaf Qyaf Qyaf Qyaf Qyaf Qi1 Qi1 Qi1 Qi1 Qi1 Qi1 Qi2 Qi1 Qi2 Qi1 Qsf Qsf Qi1 Qsf Qi1 Qsf Qi1 Qi1 Qi1 Qsf Qsf Qsf QTsd Qyaf Qyaf Qy2 Qy2 Qyaf Tsp Qy1 Tsp Qi3r Qy1 QTsa QTsa Qi2 Qy2 Qyaf Qy2 Qy2 Tsp QTsr QTsr QTsd Qy3 Qy2 Qy2r Qy3r Qys Qi1 Qi2 Qi2 Qi2 Qi2 QTsd Qys Qi3r Qsf Qyc Qsf Qsf Qsf Qy2 Qi1 Qi1 Qi1 Qi1 Qi2 Qi2 Qi2 Qy1 110°7'30"W 110°7'30"W 110°10'0"W 110°10'0"W 110°12'30"W 110°12'30"W 110°15'0"W 110°15'0"W 32°0'0"N 32°0'0"N 31°57'30"N 31°57'30"N 31°55'0"N 31°55'0"N 31°52'30"N 31°52'30"N 571000 571000 572000 572000 573000 573000 574000 574000 575000 575000 576000 576000 577000 577000 578000 578000 579000 579000 580000 580000 581000 581000 582000 582000 583000 583000 3527000 3527000 3528000 3528000 3529000 3529000 3530000 3530000 3531000 3531000 3532000 3532000 3533000 3533000 3534000 3534000 3535000 3535000 3536000 3536000 3537000 3537000 3538000 3538000 3539000 3540000 3540000 3541000 3541000 Map Symbols Contact, accurate Contact, approximate Contact, concealed SCALE 1:24,000 Topographic base map derived from the Saint David 7.5' USGS topographic quadrangle map originally with NAD27 datum. Reprojected to UTM NAD83 datum (zone 12) using iGage All Topo Maps V9. UTM NAD 83 grid and lat-lon markers produced using ESRI ArcMap v. 10.4. 1 0 1 0.5 Miles 1 0 1 0.5 Kilometers 0 1000 2000 3000 4000 5000 Feet CONTOUR INTERVAL 20 FEET Youberg Cook and Youberg LAND GALLETA FLAT EAST SAN PEDRO RANCH KNOB HILL HABERSTOCK HILL BENSON SAINT DAVID DRAGOON MCGREW SPRING § ¨ ¦ 10 ¬ « 80 ¬ « 80 Location of map area ! ! ! _ Tucson Sierra Vista Phoenix Safford Willcox Flagstaff Arizona Geological Survey 1955 East Sixth Street, PO Box 210184 Tucson, AZ 85721 (520) 621-2470 www.azgs.az.gov Geologic map of the Saint David 7 ½' Quadrangle, Cochise County, Arizona Ann M. Youberg and Joseph P. Cook Arizona Geological Survey Digital Geologic Map 48 (DGM-48), version 3.0 September 2018 1:24,000 scale Citation for this map: Youberg, A.M., Cook, J.P., 2018, Geologic Map of the Saint David 7½' Quadrangle, Cochise County, Arizona: Arizona Geological Survey Digital Geologic Map 48 (DGM-48), version 3.0, 1 sheet, layout scale 1:24,000 Research supported by the U.S. Geological Survey, National Cooperative Geologic Mapping Program, under USGS award #04HQAG0072. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. government. The Arizona Department of Water Resources provided funding for map revisions depicted in DGM-51, version 2.0. Acknowledgements: Thank you to Dr. Max Kartchner for providing access to the lower piedmont east of the town of Saint David, and to Dragoon Mountain Ranch for gate access. Pleistocene Holocene Pliocene Piedmont alluvium and surficial deposits San Pedro River alluvium Qi3 Qi2 Qi2r Qi1r Qy2r Qy1r Qycr Qy3r Qi1 Qi3r Qi3rb Qi3ra Qy2 Qy1 Qyc Qy3 Qys Qyaf d Tertiary Correlation of map units Qsf QTsd Quaternary QTsr QTcr QTsa QTsl QTsc Tss Tsp Map Unit Descriptions Piedmont deposits Basin fill deposits Other Units Historical river terrace deposits - Unconsolidated sand, gravel, and silt deposits on low terraces inset below the abandoned early historical floodplain. Qy3r Latest Holocene to historical river terrace deposits - Silt, clay, sand, and minor gravel deposits underlying the early historical floodplain. Qy2r Late to early Holocene river terrace deposits - Silt, clay, sand, and minor gravel terrace deposits slightly above the early historical floodplain. Qy1r Late Pleistocene river terrace deposits - Gravelly, sandy river terrace deposits from 5 to 20 m above the active river channel. Qi3r Late Pleistocene river terrace deposits (younger member) Qi3rb Late Pleistocene river terrace deposits (older member) Qi3ra Middle to late Pleistocene river terrace deposits (undivided) - Higher intermediate terraces composed of a mix of river gravel, sand, silt, and clay from 15 to 35 m above the active river channel. Qi2r Early to middle Pleistocene river terrace deposits - Isolated deposits covered with well-rounded river gravel from 30 to 60 m above the active river channel. Qi1r Pliocene to early Pleistocene river deposits - A moderately thick sequence of old San Pedro River deposits that underlies Qi2r terrace fan deposits. These deposits consist of river sand, silt, pebbles and cobbles. Hillslopes are generally covered with a course rounded pebble and cobble lag. Limited exposures of the deposit indicate a finer-grained sequence beneath the lag. Clasts within this unit typically have thin carbonate rinds. The soil is violently effervescent. This unit probably interfingers with the basin fill units. QTsr Ancestral San Pedro River channel conglomerates - Ancestral San Pedro River channel deposits consisting of consolidated moderately to well-sorted, rounded pebbles and cobbles. Diverse lithology reflects the larger drainage area of the San Pedro River as compared to local tributary streams. These channel conglomerates exhibit trough cross-bedding with a north-south trend. On the west side of the river these deposits are located below Qi2r within unit QTsr. East of the river these units sit directly on the lowest basin fill unit, Tsp. Smith (1994) places this unit in Deposition Interval II; it correlates to the middle St. David Formation of Grey (1967). QTcr Modern stream channel deposits - Active channel deposits composed of very poorly-sorted sand, pebbles, and cobbles with some boulders to moderately-sorted sand and pebbles Qyc Latest Holocene alluvium - Unconsolidated, very poorly sorted silty to cobbly low terrace and overflow channel deposits. Qy3 Late Holocene alluvium, active fan deposits - Active portions of young fan deposits exhibiting distributary drainage patterns Qyaf Late Holocene alluvium - Young deposits in floodplains, low terraces and small channels that are part of the modern drainage system. Qy2 Older Holocene alluvium - Planar to undulating terrace deposits standing higher than adjacent Qy2 surfaces found mostly along the margins of incised drainages. Qy1 Fine-grained Holocene alluvium derived from the Saint David Formation - Holocene alluvium derived from distal Saint David basin fill deposits. Qys Late Pleistocene alluvial fan and terrace deposits - Slightly dissected, fairly smooth terraces and alluvial fans consisting of pebbles, cobbles, and finer-grained sediment exhibiting weak rock varnish. Qi3 Middle to late Pleistocene alluvial fan and terrace deposits - Moderately dissected relict alluvial fans and terraces with moderate to strong soil development and moderately varnished surface clasts. Qi2 Early to middle Pleistocene alluvial fan and terrace deposits - Moderately to deeply dissected relict alluvial fans with strong soil development and moderately to strongly varnished surface clasts. Qi1 St. David Formation, undivided - Undivided St. David formation. Unit QTsd is composed of the following basin fill units. QTsd Piedmont alluvial fan deposits of the St. David Formation - Stacked, tabular, poorly sorted silty sandy conglomerate separated by thinner (typically < 1 m) beds of finer-grained deposits with reddish paleosols or pebbly sand beds to thinly bedded (< 0.5 m), stacked distal fan deposits of sands and gravels. Qsf Piedmont alluvial deposits of the St. David Formation - Alluvial fan and channels deposits that grade into floodplain and marsh deposits towards the basin center.Sandstone and sandy conglomerate interbedded with silty sand and vadose paleosols to hydromorphic paleosols interbedded with tuff, marl, limestone and mudstone. QTsa Limestones and mudstones of the St. David Formation - Pond and groundwater deposited limestone beds interbedded with red and green mudstone. QTsl Piedmont channel conglomerates of the St. David Formation - Consolidated, matrix supported, moderately to well-sorted, sub-angular to rounded pebble, cobbles and sand. QTsc Sandflat deposits of the St. David Formation - Massive to bedded, reddish brown (5YR to 10YR) sandstone, siltstone, and mudstone. Tss Pliocene playa deposits of the St. David Formation - Red (5 to 10 YR) clay and silt with minor interbedded sand and occasional gypsum deposits. Tsp Disturbed ground - Heavily disturbed ground due to agriculture, extensive excavation, or construction of earth dams. d Plowed areas - Historically or actively plowed fields, irrigated pastures, and other lightly disturbed ground. San Pedro River deposits Active river channel deposits - Unconsolidated, very poorly sorted sandy to cobbly beds in active river channels. Qycr
