Ichnology of Lower Jurassic beach deposits in the Shemshak Formation at Shahmirzad,southeastern Alborz Mountains,Iran |
| |
Authors: | Franz T Fürsich Markus Wilmsen Kazem Seyed-Emami |
| |
Institution: | 1. Institut für Pal?ontologie der Universit?t Würzburg, Pleicherwall 1, 97070, Würzburg, Germany 2. School of Mining Engineering, University College of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran, Iran
|
| |
Abstract: | A 19 m thick package of well-sorted lowermost Jurassic (Hettangian-Lower Sinemurian?) sandstones within the Shemshak Formation
of the southeastern Alborz Mountains displays features characteristic of foreshore to upper shoreface environments such as
tabular bedding, low-angle lamination, trough cross-stratification, parting lineation, and oscillation ripples. In contrast
to most other beach successions recorded in the literature the sandstones contain a trace fossil assemblage characterised
by low abundance but comparatively high diversity. The assemblage, comprising 14 ichnotaxa, is dominated by Palaeophycus heberti, Rhizocorallium irregulare, Gyrochorte comosa, and Parahaentzschelinia surlyki. Contrary to predictions, which assume a dominance of suspension-feeders in such high-energy environments, the trace fossil
assemblage represents a variety of ethological groups ranging from suspension-feeders to deposit-feeders, detritus-feeders,
scavengers, and a possible trap constructor (Ctenopholeus), whereby deposit-feeders predominate. This anomaly is explained by a high amount of organic detritus in the sediment, indicated
by abundant plant material, and a position of the beach in the vicinity of a river mouth. |
| |
Keywords: | Jurassic Shemshak Formation Alborz Mountains Trace fossils Beach |
本文献已被 SpringerLink 等数据库收录! |
|