Ecological Land Type

ELT 170a

Area:

3127 ha

Area in acres:

7729 acres

Elevation Range

Minimum:

924 m

Minimum in ft:

3031 ft

Maximum:

1136 m

Maximum in ft:

3728 ft

Median:

1002 m

Median in ft:

3287 ft

Soil Summary:

very deep, very gravelly and gravelly clay loams, clays, and sandy loams, lime throughout or prevalent at a shallow depth, well developed; also included are very deep sandy loam soils associated with washes and recent alluvial terraces, these soils have little or no development and lack lime in the upper soil layers; dominated by Pima County soil survey map units 6 (Bernardino-Tombstone association, 5 to 16 percent slopes), 79 (Tombstone very gravelly loam, 15 to 50 percent slopes), and 19 (Comoro sandy loam, 0 to2 percent slopes)

Geologic Materials:

alluvium and residuum associated with Quaternary and Tertiary sandstone, siltstone and conglomerate, undivided (QTs) and Holocene piedmont alluvium (Qy) which comprise 90% and 9% of the unit, respectively

Landforms:

finely dissected, weakly to moderately incised fan and pediment surfaces

Land Type Association: LTA 170

Ecological Unit: Chihuahuan desert on fans, terraces and weakly consolidated pediments

Map with the ELT 170a polygon highlighted.

Landform position classes and corresponding vegetation*

Landform Class	Area	Percentage of ELT	Vegetation and notes
nearly level plateaus or terrace	951 ha	30	whitethorn acacia dominant, with prickly pear and Isocoma
valley flats (or water bodies)	169 ha	5	whitethorn acacia dominant, with mesquite
gently sloping ridges and hills	1749 ha	56	whitethorn acacia dominant, with prickly pear and Isocoma
toe slopes, bottoms, and swales	196 ha	6	whitethorn acacia dominant, with mesquite