A metasomatic setting,the Russian River Arch,and gravitational emplacement in the history of eclogites at the classic eclogite locality of Jenner,California, USA     

Loren A. Raymond 《International Geology Review》2017,59(5-6):577-598

ABSTRACT

Blocks of metamorphic rock designated as ‘high-grade’ blocks, commonly less than 100 m in diameter, consisting of garnet-glaucophane- and hornblende-schists and gneisses and rare eclogite, are widely distributed within mélanges of the Franciscan (accretionary) Complex of California. Eclogite-glaucophane schist blocks present at Jenner, California, have been studied for petrographic, geochemical, structural, and age characteristics, but their relationship to associated Franciscan rocks is poorly understood. The studied blocks are not in situ, but rather occur in landslide deposits and beach sands. The landslide deposits overlie the low to middle slope exposures of sandstone-rich broken formations of the Franciscan Complex that are not known to contain high-grade blocks. Geochemical studies suggest a serpentinite host for the blocks. Upslope, a serpentinite-matrix mélange contains numerous high-grade blocks, including rare retrograded eclogite, and is the likely block source. The Jenner terrain as a whole was uplifted relative to rocks to the north and south near Annapolis and Freestone, respectively, by uplift along the post-Pliocene Russian River (anticlinal) Arch, as indicated by the regional distribution of arching, wave-cut, post-Franciscan surfaces with overlying Miocene/Pliocene marine sedimentary rocks. Local uplift increased landsliding and colluvial downslope movement of the blocks. In addition, local, wave-influenced transportation of smaller blocks, together with the downslope mass movements, brought the high-grade blocks to their present positions. The high-grade blocks are thus displaced from upslope exposures of the original serpentinite-matrix mélange host, in which the blocks likely experienced the metasomatism that converted eclogite to glaucophane schist. In general, the relationship of blocks to the original serpentinite host is a critical element of subduction zone architecture related to subduction zone processes and history, and should be analysed, in any studies that seek to explain the architecture and history of any accretionary complex with similar high-grade blocks.  相似文献   

Sources of high-chloride water and managed aquifer recharge in an alluvial aquifer in California,USA     

David R. O’Leary  John A. Izbicki  Loren F. Metzger 《Hydrogeology Journal》2015,23(7):1515-1533

  相似文献   

An Interdisciplinary Methodology for the Characterization and Visualization of the Heritage of Roadway Corridors          下载免费PDF全文

Mar Loren‐Méndez  Rafael Mata‐Olmo  Rita Ruiz  Daniel Pinzón‐Ayala 《Geographical review》2016,106(4):489-515

Roads, particularly since the advent of motorized traffic, have hugely impacted contemporary landscapes. Although their significance was noted in the 1980s, specific roadway‐heritage studies are scarce. Research in different disciplines has identified certain features of roads, but an integrated approach to roadway heritage or a consensus on what this constitutes are lacking. This article proposes an interdisciplinary methodology to assess roadway heritage. Roadways are interpreted within the framework of semantic openness that currently characterizes heritage studies, territory being the basic element of interpretation. Rather than a fragmented approach to conservation, the research defines integrated heritage configurations where natural, cultural, and historical features combine to produce a cohesive form of heritage. GIS (Geographical information systems) technology is used with an online database to assess the complexity of roadway heritage. ICT (Information and communications technology) strategies to raise public awareness are outlined. The methodology is applied to assess the historical N‐340 Mediterranean roadway corridor in Spain.  相似文献   

Geoarchaeological context of late Pleistocene and early Holocene occupation at the Cooper's Ferry site,western Idaho,USA     

Loren G. Davis  Charles E. Schweger 《Geoarchaeology》2004,19(7):685-704

Archaeological excavations at the Cooper's Ferry site (10IH73), located in the lower Salmon River canyon of western Idaho, revealed a stratified sequence of cultural occupations that included a pit feature containing stemmed points. However, radiocarbon ages determined on charcoal and bone in the pit feature range between ca. 12,000 yr B.P. and 7300 yr B.P. By considering the effects of postdepositional processes on dated samples, and by comparing the lithostratigraphy, pedostratigraphy, and stable isotope geochemistry of pedogenic carbonates from Cooper's Ferry with other well‐dated stratigraphic sections in the canyon, site geochronology is clarified. Based on the presence of key radiocarbon ages and distinctive stratigraphic criteria, we argue that the initial occupation and interment of lithic artifacts in a pit feature at Cooper's Ferry occurred during the late Pleistocene, between ca. 11,410 and 11,370 yr B.P., and not during the early Holocene. Records of geomorphic change and paleoenvironmental proxy data from the site reveal that early occupation in the lower Salmon River canyon corresponds with evolving riparian ecosystems, which must be considered as a contextual aspect of local prehistoric cultural ecology. © 2004 Wiley Periodicals, Inc.  相似文献   

Proposed GSSP for the base of Cambrian Stage 9, coinciding with the first appearance of <Emphasis Type="Italic">Agnostotes orientalis</Emphasis>, at Duibian,Zhejiang, China     

ShanChi Peng  Loren E. Babcock  JingXun Zuo  HuanLing Lin  XueJian Zhu  XianFeng Yang  YuPing Qi  Gabriella Bagnoli  LongWu Wang 《中国科学D辑(英文版)》2009,52(4):434-451

Exposed in natural outcrops near the Duibian Village, Jiangshan County, Zhejiang Province, China, the Duibian B section is proposed as the boundary stratotype for the base of an unnamed stage termed provisionally Cambrian Stage 9. The proposed position of the GSSP is 108.12 m above the base of the Huayansi Formation, at a horizon coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalis. This horizon coincides also with the first appearance of the cosmopolitan polymerid trilobite Irvingella angustilimbata. The section fulfills all the requirements for a GSSP, and the horizon can be constrained not only by the primary stratigraphic marker (A. orientalis) but also with secondary biostratigraphic, chemostratigraphic, and sequence-stratigraphic correlation tools. The first appearance of A. orientalis is one of the most readily recognizable levels in Cambrian, and can be correlated with precision to all paleocontinents. Supported by Chinese Academy of Sciences (Grant No. KZCX2-YW-122), the Ministry of Science and Technology of China (Grant Nos. 2006FY120300, 2006CB806400), National Natural Science Foundation of China (Grant Nos. 40072003, 40023002, 40332018, 40672023, 40602002), and the U.S. National Science Foundation (Grant No. EAR-0106883)  相似文献   

Earth observations during space shuttle flight STS‐31: The earth from 600 km     

Cynthia A. Evans  Mark A. Chambers  Michael R. Helfert  Kamlesh P. Lulla  Charles A. Wood  Loren J. Shriver 《国际地球制图》2013,28(3):99-111

  相似文献   

Earth observations during space shuttle flight STS‐46: Atlantis ’ mission to planet earth (July 31‐August 8, 1992)     

Kamlesh Lulla  David Amsbury  M. Justin Wilkinson  Cynthia Evans  Steve Ackleson  Loren J. Shriver Commander 《国际地球制图》2013,28(3):67-80

  相似文献   

Global standard names for the Lowermost Cambrian Series and Stage     

Ed Landing Shanchi Peng Loren E. Babcock Gerd Geyer Malgorzata Moczydlowska- Vidal 《《幕》》2007,30(4):287-289

  相似文献   

Kaili Biota: A Taphonomic Window on Diversification of Metazoans from the Basal Middle Cambrian: Guizhou, China   总被引：12，自引：0，他引：12  

Loren E. BABCOCK  Ronald L. PARSLEY 《《地质学报》英文版》2005,79(6):751-765

1 Introduction The Burgess Shale Biota was discovered in the Cambrian strata of western Canada by American paleontologist C. D. Walcott in 1909 (Walcott, 1911). The fauna contains more than 140 metazoan genera (Robison, 1991, Briggs et al., 1994), with a preservational range from hard skeletal parts, non-mineralized remains and internal soft-tissue and soft-body remains. Following that discovery up to 40 similar taphonomic locations have been found globally in Lower and Middle Cambrian …  相似文献   

Episodic accretion and plutonism in southwestern Alaska     

Loren A. Raymond 《Earth and Planetary Science Letters》1980,49(1):29-33

Paleontologic and radiometric dating of the accretionary prism and magmatic arc of southwestern Alaska reveal an history of episodic accretion and plutonism. Possible accretion events in the Triassic (220-195 m.y.) and Early Jurassic (184-176 m.y.) were followed by Middle Cretaceous (108-83 m.y.), earliest Paleogene (65-60 m.y.), Middle Paleogene (50-40 m.y.), and Neogene (25-0 m.y.) accretion episodes. Plutonic events, which alternate with the accretion events, occurred in the Early Jurassic (193-184 m.y.), Middle/Late Jurassic (176-145 m.y.), Late Cretaceous/Early Paleogene (83-50 m.y.), and Late Paleogene (38-26 m.y.). Episodicity of accretion events is an apparent cause of incomplete stratigraphic records in the accretionary prism and forearc basin.  相似文献