CONTACT INFORMATION Mining Records Curator Arizona Geological Survey 416 W. Congress St., Suite 100 Tucson, Arizona 85701 602-771-1601 http://www.azgs.az.gov [email protected] The following file is part of the Grover Heinrichs Mining Collection ACCESS STATEMENT These digitized collections are accessible for purposes of education and research. We have indicated what we know about copyright and rights of privacy, publicity, or trademark. Due to the nature of archival collections, we are not always able to identify this information. We are eager to hear from any rights owners, so that we may obtain accurate information. Upon request, we will remove material from public view while we address a rights issue. CONSTRAINTS STATEMENT The Arizona Geological Survey does not claim to control all rights for all materials in its collection. These rights include, but are not limited to: copyright, privacy rights, and cultural protection rights. 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" ~I~:E~AL" INF SERVICE STATE OF CALIFORNIA DIVISION OF MINES / Geologvof Northeastern California The recently published Al turas sheet of the new Because of the scarci ty of geologic data for this Geologic Map of California shows the geology of a area about three quarters of the Alturas · sheet was very interesting area in the northeastern corner of mapped on a reconnaissance basis by Division of the State, at the scale of 1:250,000 (about four Mines geologists in 1957 and 1958. The new Alturas miles to the inch). A variety of Tertiary and Qua­ sheet, with the Explanatory Data Sheet which accom­ ternary volCanic rocks , mainly olivine basalt flows panies it, is therefore the first published account and andesi tic pyroclastic rocks, cover most of the of much of the geology in the area. area of the Alturas sheet. The only pre-Tertiary Base map for the Alturas sheet is the recently uni ts are . pre- Cretaceous metamorphic rocks, which published Army Map Service Alturas sheet, series V- occur onl;y in the extreme southwest corner of the 502 , wi th 200-foot contour interval, and 100-foot area; no unmetamorphosed marine sedimentary rocks or supplementary contours. The sheet extends from 41 grani tic intrusive rocks are known to crop out in the to 42 degree s north latitude, and from 120 to 122 map area. The physiography of the area is dominated degrees west longi tude, and includes about 7200 squa,re by two main features: (1) a series of prominent scarps mile s. It is bounded by Or egon on the nor th and of mid-Tertiary normal faults which bound the many Nevada on t he east, and includes all of Modoc County, north- trending fault- block mountains and ridges in and parts of Siskiyou, Shasta, and Lassen Counties. the area, and (2) vast floods of Quaternary basal tic lava that overlapped the fault-blocks and have been A variety of landforms and physiographic features relatively little deformed. occurs in this part of northeastern California. Por- Conical pinnacles, "chimney rocks", formed by wind and water erosion in pumiceous rhyolitic tuff loJ. on the west flank of the Warner Range. Flat surface at left side is edge of Devils Garden plateau, surfaced with Pleistocene basalt flows. 2 California State Division of Mines (Vol. 12 The range consists mainly of l ayered andesitic pyroclastic rocks--tuff, ' tuff- br eccias, agglomer- _ MINERAL INFORMATION SERVICE a tes--with intermingled andesitic flows. These rocks , _ State of California Edmund G. Brown, Governor which have been termed t he Cedarville series, include Department of Natural Resources DeWitt Nelson, Director Oligocene and Miocene units, and are the oldest known Division of Mines Ian Campbell, Chief rocks in the Alturas sheet, except for a small area Headquarters office: Ferry Building, San Francisco 11 of Mesozoic and Eocene r ocks in the southwest corner Branch offices: of the sheet. In the northern end of the range , near State Build ing, 217 W. First St., los Angeles the Oregon bor der, a series of rhyolitic r ocks is Business and Professions Annex, 1021 0 St., Sacramento present as flows and shallow intrusions into the Natural Resources Bu ilding, Cypress and lanning Sis., Redding andesi tesj masse s of obsidian and perli te also are present. In the southern portion of the Warner Range, MINERAL INFORMATION SERVICE is designed to in­ and on its western flank , basaltic and andesitic form the public on the geology and mineral resources of Cali­ flow r ocks were poured forth in late Tertiar y and fornia and on the usefulness of minerals and rocks, and to serve Pleistocene time to cover large areas of the Cedar- as a news release on mineral discoveries, mining operations, mar­ ville rocks. Uplift of the Warner Range appar ently kets, statistics, and new publications. It is issued monthly by the California Division of Mines. Subscription price, January through began in mid-Tertiary time with a combination of December, is $1.00. arching, tilting, and up l ifting forces. Although faults bound the Warner Range on both sides, like Other publications of the Division of Mines include the Annual Report of the State Mineralogist, the Bulletin and Special Report t he Sierra Nevada, the east scar p is conspicuously senes, county reports, and maps. A list of the Division's available abrupt, wher eas the western flank of the southern publications will be sent upon request. Communications to the part of the range slopes r elatively gradually. Near Division of Mines, including orders for publications, should be the south border of the Alturas sheet , decreased up- addressed to the headquarters office. lift of the Warner Range causes i t to blend gradually with an irregular terrane of Pliocene shield volca- noes and intervening fiat plains once filled with large Quaternary lakes, which extend for many miles south of the Alturas sheet. The central portion of the Alturas shee t, which tions of four geomo r phic provinces ar e r epr esented, comprises about two-thirds of its area, is in the each char acter ized by distinctive surface features Modoc Plateau province, character ized by extensive and a unique geological r ecord . The four provi nces Tertiary and Quaternary basaltic lava flows, volca­ represented are (1) the Basin-Ranges pr ovince; (2 ) noes, and cinder cones. The principal plateau dis- t he Modo c Plateau province; (J) t he Cascade Range trict, known as the Devils Garden , occupies nearly e province; and (4) the Klama t h Moun tains province . 1000 square miles in the north centr al part of the area. Here, floods of olivine basalt formed a ve- The easter nmos t part of the Alturas sheet area is neer from several tens to several hundreds of feet part of the Basin-Ranges province , where the tilted thick over the diatomaceous and ash-rich lake- and Warner Range fault block has been uplifted some 5500 stream-laid sediments that are known as the Al turas feet above t he floor of the adjacent Surprise Va lley formation. fault block, with a spectacular range-front scarp marking the line of the Surprise Valley fault . De ­ Much of the Devils Garden plateau is bordered by sert conditions prevail east of the War ne r Range , an abr upt cliff several hundred feet high, whe r e the wi th periodically desiccated al kali lakes , sal t ­ soft underlying Alturas sediments have been eroded fla ts, and unusual wi nd-formed hummocks and migra ting away , leaving a br oad valley. The edges of the ba­ sand dunes pr esent on the dry, sagebrush-covered por­ sal t flows that cover the plateau surface for m a tions of the floor of Surprise Valley. Ar ound the conspicuous dark-colored rimrock at the top of the margins of Surprise Valley are preserved remnants plateau- border ing Cliffs . Diatoms and vertebrate of shorelines and terr aces, some as high as 550 feet fossil s (mainly mouse teeth) found just below the above the valley floor, left ther e by Lake Surprise, r imrock indicate a late Pliocene to early Pleistocene which occupied the valley in Pleistocene time, and age for these sediments ; the overlying basalt flows which was contempor aneous wi th Lake Lahontan , an ex­ are considered to be Pleistocene . In thi s rela ti vely tensive Pleistocene lake which occupied much of Ne ­ arid part of the Alturas sheet area, the youthful vada and Utah . lava pl ateau surface supports only a sparse vegeta­ tion, mainly of juni per t r ees and sagebrush . Parts The uplifted Warner Range block, wi th its highest of the plateau are covered wi th clusters of conspic­ peaks onl y slightly less than ten thousand feet in uous circular soil mounds, from 4 to 5 feet high and elevation, is the most prominent feature in the east­ from 30 to 4c feet in diameter.