干旱区生态环境知识资源中心(Arid): Evidence of early Miocene synextensional volcanism and deposition in the northern Calico Mountains, central Mojave metamorphic core complex, southern California, USA

Arid

DOI	10.1130/GES02356.1
	Evidence of early Miocene synextensional volcanism and deposition in the northern Calico Mountains, central Mojave metamorphic core complex, southern California, USA
	Murray, Bryan P.; Hames, Willis E.
通讯作者	Murray, BP (corresponding author), Calif State Polytech Univ Pomona, Dept Geol Sci, 3801 W Temple Ave, Pomona, CA 91768 USA.
来源期刊	GEOSPHERE
ISSN	1553-040X
出版年	2021
卷号	17 期号:4 页码:1007-1037
英文摘要	The spatiotemporal link between large-scale continental crustal extension and magmatic activity has been identified by numerous past studies, yet commonly the details of these associations remain unresolved. This study in the central Mojave metamorphic core complex (CMMCC) of southern California (USA) presents new geologic mapping, stratigraphic interpretations, and Ar-40/Ar-39 geochronology of the Jackhammer and Pickhandle Formations in the northern Calico Mountains to provide additional age constraints on the relative timing of early Miocene volcanism, deposition, and extension. The Jackhammer Formation, the oldest Tertiary stratigraphic unit, is nonconformable with pre-Cenozoic nonmylonitic metasedimentary and plutonic basement rocks and consists primarily of alluvial deposits and primary to reworked silicic tuffs, interbedded locally with basement-derived avalanche megabreccia, lacustrine limestone, and mafic lava; in addition, the Mammut ignimbrite, an similar to 130-m-thick crystal-rich welded lapilli tuff, is exposed only in the eastern part of the study area and appears to transition laterally into thinner, nonwelded lapilli tuff similar to 6 km to the west. The Pickhandle Formation conformably overlies the Jackhammer Formation and consists of: (1) a lower assemblage composed of reddish monomictic debris-flow breccias with porphyritic rhyodacitic clasts and silicic block-and-ash-flow deposits of similar composition; and (2) an upper assemblage of polymictic (metaplutonic basement and rhyodacite) alluvial deposits, primary to reworked lapilli tuff, and local rhyodacitic lava and block-and-ash flows. Rhyodacitic lava domes were emplaced during the final stages of Pickhandle Formation deposition, primarily intruded along preexisting normal fault zones. Sedimentary and volcanic lithofacies suggest that the Jackhammer and Pickhandle Formations were deposited in a volcanic vent-proximal alluvial fan system that formed within a half-graben basin bounded on the east by the southwest-dipping Amphitheatre fault. Growth strata within the hanging-wall deposits, primarily southwest-directed paleocurrents, and interbedded alluvial debris-flow, basement-derived mega-breccia, and lacustrine deposits adjacent to this fault suggest synextensional deposition in an intra-hanging-wall basin that developed during upper-plate extension in the CMMCC. New Ar-40/Ar-39 ages for six samples of silicic pyroclastic flows and a lava dome from the synextensional Pickhandle and Jackhammer Formations in the Calico Mountains have a mean age of 20.10 +/- 0.06 Ma. This age is 3-4 m.y. younger than the maximum age of initial extension determined by previous studies in other areas of the central Mojave, suggesting that CMMCC extension was not a synchronous large-magnitude regional event. Rather, extension and contemporaneous volcanism was more localized and asynchronous across the region, occurring in many smaller extensional basins that eventually culminated in exposure of the CMMCC mylonitic footwall rocks.
类型	Article
语种	英语
开放获取类型	gold
收录类别	SCI-E
WOS记录号	WOS:000678073000004
WOS关键词	BARSTOW FORMATION ; DESERT ; EXTENSION ; MAGNITUDE ; EVOLUTION ; GEOCHRONOLOGY ; EXAMPLE ; BLOCK
WOS类目	Geosciences, Multidisciplinary
WOS研究方向	Geology
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/363440
作者单位	[Murray, Bryan P.] Calif State Polytech Univ Pomona, Dept Geol Sci, 3801 W Temple Ave, Pomona, CA 91768 USA; [Hames, Willis E.] Auburn Univ, Dept Geosci, 2050 Beard Eaves Coliseum, Auburn, AL 36849 USA
推荐引用方式 GB/T 7714	Murray, Bryan P.,Hames, Willis E.. Evidence of early Miocene synextensional volcanism and deposition in the northern Calico Mountains, central Mojave metamorphic core complex, southern California, USA[J],2021,17(4):1007-1037.
APA	Murray, Bryan P.,&Hames, Willis E..(2021).Evidence of early Miocene synextensional volcanism and deposition in the northern Calico Mountains, central Mojave metamorphic core complex, southern California, USA.GEOSPHERE,17(4),1007-1037.
MLA	Murray, Bryan P.,et al."Evidence of early Miocene synextensional volcanism and deposition in the northern Calico Mountains, central Mojave metamorphic core complex, southern California, USA".GEOSPHERE 17.4(2021):1007-1037.