DOI: 10.1016/j.palaeo.2015.12.011
论文题名: Buried or brined? Eurypterids and evaporites in the Silurian Appalachian basin
作者: Vrazo M.B. ; Brett C.E. ; Ciurca S.J.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2016
卷: 444 起始页码: 48
结束页码: 59
语种: 英语
英文关键词: Arthropod paleoecology hypersalinity
; Diagenesis
; Eurypterus
; Salina/Bertie groups
; Salt hopper
英文摘要: Eurypterid-bearing deposits from the late Silurian Appalachian basin are often interpreted as having been deposited under hypersaline conditions. These interpretations are based on the close association of abundant eurypterid remains with evaporite deposits and structures such as salt hoppers in the Salina and Bertie groups. To determine whether this association reflects life habitat, or is the result of taphonomic or diagenetic processes, the co-occurrence of eurypterids and salt hoppers in the upper Silurian Appalachian basin was examined at several stratigraphic scales. A survey of eurypterid remains from the prolific Ellicott Creek Breccia Member of the Fiddler's Green Formation (Bertie Group) found that 2% of the 479 specimens surveyed are crosscut by salt hoppers or incipient halite structures. In a regional survey, displacive salt hoppers occurred in the same bed as eurypterid remains in 37% (19:51) of all eurypterid-bearing units. In these units, salt hoppers were typically the only structures found intimately associated with eurypterids, sometimes crosscutting them. The disruptive nature of the hoppers in the Ellicott Creek Breccia, for example, suggests that they formed within the sediment rather than at the air-water interface, and that organic remains might have acted as nucleation points for developing halite crystals. To explain these associations, we present a depositional model in which displacive salt hoppers formed within NaCl-saturated groundwater as a result of surface evaporation in the vadose zone during regressive phases, and only after eurypterid remains were buried. In this scenario, the intimate association of eurypterids and salt hoppers in these deposits reflects early-stage diagenetic overprinting rather than conditions during life. Our model largely refutes the hypothesis that eurypterids were halotolerant organisms based on their co-occurrence with salt hoppers. We conclude that eurypterids preserved in upper Silurian carbonate ramp deposits were primarily denizens of more normal marine or hyposaline subtidal settings. © 2015 Elsevier B.V.. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/68585
Appears in Collections: 过去全球变化的重建
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作者单位: Department of Geology, University of Cincinnati, 500 Geology/Physics Building, Cincinnati, OH, United States; 2457 Culver Road, Rochester, NY, United States
Recommended Citation:
Vrazo M.B.,Brett C.E.,Ciurca S.J.. Buried or brined? Eurypterids and evaporites in the Silurian Appalachian basin[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2016-01-01,444