Storm-generated depositional types and associated trace fossils in Lower Carboniferous shallow-marine carbonates of Three Cliffs Bay and Ogmore-by-Sea, South Wales

1982 ◽  
Vol 39 (3-4) ◽  
pp. 187-202 ◽  
Author(s):  
Xian-tao Wu
Keyword(s):  
Trace Fossils ◽  
Lower Carboniferous ◽  
Shallow Marine ◽  
South Wales ◽  
Marine Carbonates

Trace fossil assemblages reflecting stressed environments in the Middle Jurassic Carmel Seaway of central Utah

1999 ◽  
Vol 73 (4) ◽  
pp. 711-720 ◽  
Author(s):  
J. M. De Gibert ◽  
A. A. Ekdale
Keyword(s):  
Benthic Community ◽  
Middle Jurassic ◽  
Trace Fossils ◽  
Trace Fossil ◽  
Pore Waters ◽  
Shallow Marine ◽  
Marine Carbonate ◽  
Marine Carbonates ◽  
Low Diversity ◽  
Fossil Assemblages

The shallow-marine Carmel Formation (Middle Jurassic) in central Utah hosts low-diversity trace fossil assemblages, including Arenicolites, Chondrites, Gyrochorte, Lockeia, Planolites, Protovirgularia, Rosselia, Scalarituba, Skolithos, Taenidium, and Teichichnus. Non specialized ichnotaxa with a remarkably small burrow size dominate the assemblages. The amount of bioturbation is lower than expected in comparison with modern shallow-marine carbonate environments. These ichnological features also are significantly different from those of other Jurassic shallow-marine carbonates. The trace fossils represent an environmentally stressed benthic community in a marginal marine, restricted setting, with salinities above normal marine and with depletion of oxygen in pore waters.

Detrital zircon age and biostratigraphic and chemostratigraphic constraints on the Ediacaran–Cambrian transitional interval in the Irkutsk Cis–Sayans Uplift, southwestern Siberian Platform

2020 ◽  
pp. 1-17
Author(s):  
Vasiliy V. Marusin ◽  
Alena A. Kolesnikova ◽  
Boris B. Kochnev ◽  
Nikolay B. Kuznetsov ◽  
Boris G. Pokrovsky ◽  
...  
Keyword(s):  
Siberian Platform ◽  
Detrital Zircon ◽  
Isotope Composition ◽  
Trace Fossils ◽  
Zircon Age ◽  
Shallow Marine ◽  
Carbonate Carbon ◽  
Carbon And Oxygen Isotope ◽  
Marine Carbonates ◽  
Isotopic Records

Abstract A number of ecological and geochemical transformations occurred during late Ediacaran and early Cambrian time, the effects of which are difficult to overestimate. However, the strong linkage of biostratigraphic and chemostratigraphic methods with lithofacies makes the localization of the Precambrian–Cambrian boundary and its correlation with lithologically contrasting sections highly debatable. We analyse the taxonomy and stratigraphic distribution of small skeletal fossils and trace fossils, the carbonate carbon and oxygen isotope composition, and U–Pb detrital zircon age in the Ediacaran–Cambrian transitional interval of the Irkutsk Cis–Sayans Uplift (southwestern Siberian Platform). This interval (Moty Group) comprises a transgressive succession with red-coloured alluvial to deltaic siliciclastic deposits (Shaman Formation) and overlying shallow-marine carbonates (Irkut Formation). The lower Irkut Formation hosts sporadic and poorly preserved tubular Cambrotubulus fossils, which are known from both the terminal Ediacaran Period (c. 550–541 Ma) and the Terreneuvian Epoch (541–521 Ma), and typical Fortunian trace fossils, including an index ichnotaxon of the Cambrian boundary Treptichnus pedum. The biostratigraphic and carbonate carbon isotope data and U–Pb concordia ages of 531.1 ± 5.2 Ma (mean weighted, 530.6 ± 5.3 Ma) of the five youngest zircon grains from the lower Irkut Formation indicate that at least the shallow-marine carbonates of the upper Moty Group correspond to the Cambrian Stage 2 (c. 529–521 Ma). In the Irkutsk Cis–Sayans Uplift, the Cambrian Period tentatively began before or during the accumulation of the alluvial to deltaic siliciclastic Khuzhir and Shaman formations, and this crucial divide remained unmarked in the palaeontological and isotopic records.

Petrology of an Irregular-Nodule Bed, Lower Carboniferous, Anglesey, North Wales

1966 ◽  
Vol 103 (6) ◽  
pp. 477-486 ◽  
Author(s):  
R. A. H. Nichols
Keyword(s):  
Trace Fossils ◽  
Lower Carboniferous ◽  
North Wales

AbstractSome of the nodules described are similar to trace-fossils described by Donaldson and Simpson and some ichnofossils described by Seilacher, but many appear to be structures produced by sedimentary boudinage. These do not seem to be a result of organic or concretionary action. It is suggested that currents deposited thin bioclastic calcarenites with interbeds of calcite silt, and that crinoids and coral patches developed only sporadically during deposition. A few scavengers reworked the bioclastic calcarenites and calcite silt layers thus forming the trace-fossils; many of the irregular-nodules, however, were probably formed by differential compaction and segregation in the calcite silt beds, and may represent sedimentary boudins, which are relicts of former layers.

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