As part of the Perris Block, the Temescal Mountains are part of its eroded mass of Cretaceous and older granitic rocks of the Southern California Batholith and metasedimentarybasement rocks. Most of this basement rock that once overlay the granitic plutons that rose up into it, has been eroded away, the remainder being found between between the similarly eroded plutons of granitic rock.
^The name Sierra Temescal, (Temescal Mountains) appears on the mountains shown east of the Santa Ana Mountains and Temescal Creek and north of the Laguna (Lake Elsinore) and Rio San Jacinto (San Jacinto River) on the 1861 Rail Road Route survey map, "From San Francisco Bay to the Plains of Los Angeles", from Explorations and Surveys made under the direction of The Hon. Jefferson Davis, Secretary of War by Lieut. John G. Parke, Topl. Engrs. assisted by Albert H. Campbell, Civil Engineer and N.H. Hutton, H. Custer and G.G. Garner. 1854 & 55. Map No. 1. Constructed and drawn by H. Custer. Explorations and Surveys for a Rail Road Route from the Mississippi River to the Pacific Ocean. War Department. Coast Route, California.
^"The expression "Temescal Range" was used in the Whitney report to define the hills lying on the northeast side of the Elsinore Valley. The range was described as follows: "The Temescal range of mountains commences on the south side of the Santa Ana River, and runs southeast in a direction nearly parallel with that chain of the same name [Santa Ana Mountains], from which it is separated by a narrow valley . . . The name Temescal seems to be limited in its application to the hills lying between the Santa Ana and the San Jacinto Creeks, and which cover an area of about 300 square miles." Rene Engel, GEOLOGY AND MINERAL DEPOSITS OF THE LAKE ELSINORE QUADRANGLE CALIFORNIA, CAIIFORNIA DEPARTMENT OF NATURAL RESOURCES, BULLETIN 146, DIVISION OF MINES, SAN FRANCISCO, 1959, p. 11-12, citing Whitney. J. D., 1865, Santa Ana and Temescal Ranges: Geol. Survey of California, 1860-64, vol. 1— Geology. p. 175-181
^"To the northeast [of the Santa Ana Mountains] the Temescal Mountains form the southwestern edge of a broad plateau area, modified by medium relief forms, which now is known as the "Perris Block." This name is derived from the town of Perris, near the center of the Elsinore quadrangle. The term "Temescal Range" was first applied by J. D. Whitney (1865, p. 178) to the mountains that extend from the Santa Ana River to San Jacinto Creek. Under this definition are included Arlington Mountain (elevation 1851 feet), Estelle Mountain (elevation 2826 feet), and the hills immediately east of Elsinore (maximum elevation 1945 feet). The writer here proposes to include in the Temescal Mountains the hills that extend to the southeast and form the natural continuation of the mountains as the western edge of the Perris Block. Engel, GEOLOGY AND MINERAL DEPOSITS OF THE LAKE ELSINORE QUADRANGLE, p. 14