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Faulted and tilted Pliocene olivine-tholeiite lavas near Alturas, NE California, and their bearing on the uplift of the Warner Range

Ian S. E. Carmichael, Rebecca A. Lange, Chris M. Hall and Paul R. Renne
Faulted and tilted Pliocene olivine-tholeiite lavas near Alturas, NE California, and their bearing on the uplift of the Warner Range
Geological Society of America Bulletin (October 2006) 118 (9-10): 1196-1211

Abstract

Late Miocene-Pliocene (8-3 Ma) olivine basalt lavas, dated in this study by the (super 40) Ar/ (super 39) Ar method, have been faulted and tilted on both the east and west sides of the Warner Range of NE California, which is itself a tilted block rising to 2960 m at its crest that is composed of Miocene-Oligocene lavas and volcaniclastic rocks. The late Miocene-Pliocene lavas, distinctively poor in K (sub 2) O and rich in MgO, are called low-K olivine tholeiites and have a different mantle source region than that of the older subduction-related lavas of the main Warner Range. Hays Canyon Range (max. elev. 2400 m) lies to the east of the Warner Range, and the broad Surprise Valley separates the two fault-bounded ranges. Middle Miocene (ca. 15 Ma) basic lavas, with a small easterly dip, cap the Hays Canyon Range and overlie Oligocene silicic ash-flow deposits and a basaltic andesite spatter volcano. Middle Miocene basic lavas also form the crest of the Warner Range and its westerly dip slope ( approximately 15 degrees ). Nearly horizontal basic lavas of the same age are also found on both sides of the Warner Range, and it is a plausible conclusion that these middle Miocene basalts were a contiguous group before faulting and uplift of the Warner Range. Derived estimates of uplift rates ( approximately 1 mm/yr) of the Warner Range indicate that uplift could have been initiated at ca. 4 Ma, a period of the most voluminous eruption of low-K olivine tholeiite lavas. If the slower Cretaceous exhumation rate of the Sierra Nevada (0.5-1.0 mm/yr) is applied to the total offset of the Warner Range (4270 m), and it did not vary with time, then the uplift of the Warner Range was initiated at ca. 8 Ma, which coincides with the age of the oldest low-K olivine tholeiite lava (8 Ma). Low-K olivine tholeiites require a hot shallow asthenospheric source, and it is the rise of this hot mantle that is presumed to have caused the uplift of the Warner Range. Whether or not the widespread eruption of small volumes of Pliocene low-K olivine tholeiites in central and eastern Oregon is associated with crustal uplift is unknown.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 118
Serial Issue: 9-10
Title: Faulted and tilted Pliocene olivine-tholeiite lavas near Alturas, NE California, and their bearing on the uplift of the Warner Range
Affiliation: University of California at Berkeley, Department of Earth and Planetary Science, Berkeley, CA, United States
Pages: 1196-1211
Published: 200610
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 48
Accession Number: 2006-071548
Categories: Structural geologyIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix
Illustration Description: illus. incl. sect., 7 tables, geol. sketch map
N41°15'00" - N42°00'00", W120°40'00" - W119°45'00"
Secondary Affiliation: University of Michigan, USA, United StatesBerkeley Geochronology Center, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200620
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