Arid
DOI10.1016/j.sedgeo.2015.04.012
Deciphering the history of hydrologic and climatic changes on carbonate lowstand surfaces: calcrete and organic-matter/evaporite facies association on a palimpsest Middle Jurassic landscape from Portugal
Azeredo, Ana C.1; Wright, V. Paul2; Mendonca-Filho, Joao3; Cristina Cabral, M.1; Duarte, Luis V.4
通讯作者Azeredo, Ana C.
来源期刊SEDIMENTARY GEOLOGY
ISSN0037-0738
EISSN1879-0968
出版年2015
卷号323页码:66-91
英文摘要

The unusual occurrence of calcretes and prominent organic matter in the Middle Jurassic (Lower Bathonian, Serra de Aire Formation) of the Lusitanian Basin of western Portugal (Western Iberian Margin) revealed a complex palimpsest exposure record, here interpreted as reflecting hydrological changes caused by phases of emergence and immersion. It serves as a potential model for understanding stratigraphic development at lowstand surfaces in carbonate successions. The exposure-dominated fades association grades upwards into peritidal and lagoonal limestones, and the interval is assigned to the regressive peak of a Transgressive-Regressive Facies Cycle (2nd order) of the thick Middle Jurassic carbonate ramp succession.


The Galinha Quarry, Fatima region, NE of Lisbon, a type section for this lowstand assemblage, exhibits varied calcretes, with black-dasts, interbedded with, and grading into: organic-rich marly/clayey seams and lenses, locally with carbonate nodules; carbonates with evaporite traces; microbial laminites; black-clast and fenestral limestones; some lithofacies are dolomitized. The palynofacies contains phytoclasts associated with less refractory, more prone to degradation components, which suggests natural combustion/pyrolysis (wild fires). The lowstand surface represents a low relief landscape with small depressions/ponds bordering a more distal marginal-littoral setting; the partly subaerial and partly subaqueous settings were subjected to lengthy exposure and to fluctuating, very shallow water bodies and water table. Coeval climatic regime was a seasonally dry/wet one, with dry/semi-arid phases dominating over the sub-humid, as shown by the combined record of intense calcrete development, rhizogenic structures, microbial mats, brecciation, desiccation, evaporites and wild fire evidence. However, sea level rise caused changes to shallow, sea-water influenced restricted lagoonal-peritidal settings.


Comparisons and differences with modern and ancient coast marginal carbonates are made to provide a guide to the variability in such lowstand deposystems in the stratigraphic record. (C) 2015 Elsevier B.V. All rights reserved.


英文关键词Calcretes Organic matter Lowstand carbonates Middle Jurassic Portugal
类型Article
语种英语
国家Portugal ; Wales ; Brazil
收录类别SCI-E
WOS记录号WOS:000356556000005
WOS关键词SUBBASIN LUSITANIAN BASIN ; DISCONTINUITY SURFACES ; PALUSTRINE CARBONATES ; BLACK PEBBLES ; FRENCH JURA ; PALYNOFACIES ; LACUSTRINE ; PALEOSOLS ; EXAMPLES ; PLATFORM
WOS类目Geology
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/2XILL650/190427
作者单位1.Univ Lisbon, Fac Ciencias, Dept & Ctr Geol, IDL, P-1749016 Lisbon, Portugal;
2.Natl Museum Wales, Nat Sci, Cardiff CF1 3NP, S Glam, Wales;
3.Univ Fed Rio de Janeiro, Inst Geociencias, Dept Geol, Ilha Fundao, BR-21949900 Rio De Janeiro, Brazil;
4.Univ Coimbra, Fac Sci & Technol, MARE Marine & Environm Sci Ctr, P-3030790 Coimbra, Portugal
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GB/T 7714
Azeredo, Ana C.,Wright, V. Paul,Mendonca-Filho, Joao,et al. Deciphering the history of hydrologic and climatic changes on carbonate lowstand surfaces: calcrete and organic-matter/evaporite facies association on a palimpsest Middle Jurassic landscape from Portugal[J],2015,323:66-91.
APA Azeredo, Ana C.,Wright, V. Paul,Mendonca-Filho, Joao,Cristina Cabral, M.,&Duarte, Luis V..(2015).Deciphering the history of hydrologic and climatic changes on carbonate lowstand surfaces: calcrete and organic-matter/evaporite facies association on a palimpsest Middle Jurassic landscape from Portugal.SEDIMENTARY GEOLOGY,323,66-91.
MLA Azeredo, Ana C.,et al."Deciphering the history of hydrologic and climatic changes on carbonate lowstand surfaces: calcrete and organic-matter/evaporite facies association on a palimpsest Middle Jurassic landscape from Portugal".SEDIMENTARY GEOLOGY 323(2015):66-91.
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