Microbial-related biogenic strutures from the Middle Ordovician slates of Canelas (northern Portugal)

A review with the description of the low diverse ichnoassembla – ges from the slates of Valongo Formation is made for the first time. Among the organic-rich mining, simple trace fossils dominated by Planolites-like worm burrows and very rare Chondrites developed in short-termed dysoxic intervals, we describe Phycodes canelensis nov. isp. as an adaptation to store faecal pellets poorer in nutrients away from the feeding area or for cultivating bacteria. The most remarkable are very large-size, concentrically ringed, pyritized structures, developed in relation with the decomposition of orthoconic cephalopods and dissolution of their shells, which are reinterpreted now as microbialites.

A review with the description of the low diverse ichnoassembla – ges from the slates of Valongo Formation is made for the first time. Among the organic-rich mining, simple trace fossils dominated by Planolites-like worm burrows and very rare Chondrites developed in short-termed dysoxic intervals, we describe Phycodes canelensis nov. isp. as an adaptation to store faecal pellets poorer in nutrients away from the feeding area or for cultivating bacteria. The most remarkable are very large-size, concentrically ringed, pyritized structures, developed in relation with the decomposition of orthoconic cephalopods and dissolution of their shells, which are reinterpreted now as microbialites.

Text: C. Neto de Carvalho, H. Couto, M. V. Figueiredo, A. Baucon
Editor: LNEG – Laboratório Nacional de Geologia e Energia IP
Edited: 2016
Linguage: Portuguese/English
ISBN: 0873-948X