DOI: 10.1016/j.palaeo.2015.07.015
论文题名: An enigmatic kilometer-scale concentration of small mytilids (Late Miocene, Guadalquivir Basin, S Spain)
作者: Aguirre J. ; Braga J.C. ; Martín J.M. ; Puga-Bernabéu T. ; Pérez-Asensio J.N. ; Sánchez-Almazo I.M. ; Génio L.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2015
卷: 436 起始页码: 199
结束页码: 213
语种: 英语
英文关键词: Carmona
; Cold seep
; El Alcor
; Heterozoan carbonates
; Mussels
英文摘要: Upper Miocene heterozoan carbonates crop out extensively in a NE-SW-trending belt (42. km long and 1.5-8. km wide) along the so-called El Alcor topographic high, from Carmona to Dos Hermanas (Seville, S Spain). These carbonates formed at the southern active margin of the Guadalquivir Basin, the foreland basin of the Betic Cordillera. They change to marls basinward (NE) and to sands landward (SE and SW). Therefore, carbonate production was constrained to a limited area in an otherwise siliciclastic shelf. The carbonates (up to 40. m thick) overlie a gradually coarsening-upward succession of marls followed by silts and sandstones. The carbonate sequence can be divided into three subunits corresponding, from bottom to top, to lowstand, transgressive, and highstand system tract deposits. The lower subunit, exhibiting extensive trough cross-bedding, is interpreted as a shallow-water bar deposit. The intermediate subunit onlaps underlying sediments and was deposited in deeper, low-turbulence conditions. The upper subunit deposits accumulated in a well-oxygenated outer platform based on benthic foraminiferal assemblages. The presence of hummocky and swaley cross-stratification in these latter deposits suggests that they were affected by storms. Pervasive fluid-escape structures are also observed throughout the carbonates. The three subunits consist of bioclastic packstones to rudstones made up of abundant fragments of small mytilids. Isotopic data from serpulid polychaete Ditrupa tubes show 13C-depleted values (up to -16.1‰), whereas δ18O yields normal marine values. Additional isotopic data on shells of scallops, oysters, and small mussels, as well as bulk sediment, show diagenetic alterations. Based on actualistic examples of massive concentrations of mussels, the nearly monospecific composition of the El Alcor deposits, together with negative δ13C values of Ditrupa tubes, indicates that cold seeps presumably promoted carbonate formation. However, the absence of typical features of cold-seep deposits, such as authigenic carbonates mediated by anaerobic bacterial activity and the typical chemosynthetic shelly organisms, makes the large carbonate body of El Alcor an unusual cold-seep deposit. © 2015 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/68840
Appears in Collections: 过去全球变化的重建
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作者单位: Dpt. Estratigrafía y Paleontología, Facultad de Ciencias, Universidad de Granada, Fuentenueva s/n, Granada, Spain; Section of Earth and Environmental Sciences, University of Geneva, Rue des Maraîchers 13, Geneva, Switzerland; Centro de Instrumentación Científica, Universidad de Granada, Fuentenueva s/n, Granada, Spain; Centro de Estudos do Ambiente e do Mar, Dpt. de Biologia, Universidade de Aveiro, Campus Universitário de Santiago, Aveiro, Portugal
Recommended Citation:
Aguirre J.,Braga J.C.,Martín J.M.,et al. An enigmatic kilometer-scale concentration of small mytilids (Late Miocene, Guadalquivir Basin, S Spain)[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2015-01-01,436