Palaeogeographical homogeneity of trace-fossil assemblages in Lower Jurassic spotted marls and limestones: comparison of the Western Carpathians and the Betic Cordillera

2021 ◽  
pp. SP514-2020-110
Author(s):  
Vladimír Šimo ◽  
Matías Reolid
Keyword(s):  
Geographical Area ◽  
Lower Jurassic ◽  
Trace Fossil ◽  
Betic Cordillera ◽  
Western Carpathians ◽  
Distinctive Morphology ◽  
Community Types ◽  
Fossil Assemblages ◽  
Tethys Ocean ◽  
Palaeoenvironmental Conditions

AbstractMicritic sediments containing dark, discrete, organic-rich burrows, situated in a light grey background carbonate mud, were deposited over a broad geographical area in deep-shelf, bathyal and basinal environments in the western margin of the Tethys Ocean during the Early and Middle Jurassic. These hemipelagic deposits represent a distinct depositional regime marked by low-energy, soft-bottom and only locally dysoxic environments. Still, it is unclear whether the trace-fossil assemblages occurring in these deposits pertain to a network of several community types – the ichnotaxa differing from basin to basin – or to a single community of environmentally broad-ranging, burrow-producing species. Lower Jurassic trace-fossil assemblages are found in the Western Carpathians and in the Subbetic, Betic Cordillera: that is, in basins separated by more than 2000 km in their original palaeogeographical areas. The stereotypical Chondrites and Zoophycos trace-fossil assemblages that occur in the analysed deposits share two ichnogenera of distinctive morphology (Lamellaeichnus and Teichichnus). Agglutinated foraminifera Bathysiphon occurs together with the described trace-fossil assemblage and determines the epibenthic palaeoenvironmental conditions. In the Western Carpathians, a Lamellaeichnus-dominated assemblage alternates with a Zoophycos-dominated assemblage in small, metre-scale cycles in the upper Pliensbachian, and the proportion of the Zoophycos assemblage increases stratigraphically upwards, probably owing to reduced basin ventilation during the early Toarcian. Within the southern Iberian palaeomargin, represented by the Betic Cordillera, Zoophycos is scarce in the facies.

Pacing of late Pliensbachian and early Toarcian carbon cycle perturbations and environmental change in the westernmost Tethys (La Cerradura section, Subbetic Zone of the Betic Cordillera, Spain)

2021 ◽  
pp. SP514-2021-27
Author(s):  
R. L. Silva ◽  
M. Ruhl ◽  
C. Barry ◽  
M. Reolid ◽  
W. Ruebsam
Keyword(s):  
Regional Climate ◽  
Geographical Area ◽  
Betic Cordillera ◽  
Content Type ◽  
Oceanic Anoxic Event ◽  
Carbon Isotopic ◽  
Detailed Assessment ◽  
Isotope Stratigraphy ◽  
Supplementary Material ◽  
Tethys Ocean

AbstractThe detailed assessment of high-resolution elemental and isotopic geochemical datasets collected from the marl-limestone alternations cropping out at La Cerradura (Subbetic domain of the Betic Cordillera, Spain) and chrono- and chemostratigraphic correlation with the reference Mochras borehole (Cardigan Bay Basin, UK) unveiled valuable new insights to the understanding of late Pliensbachian-early Toarcian palaeoenvironmental dynamics at a key geographical area between the northern European seaway and the Tethys Ocean.This study shows that deposition in the study area took place under dominantly oxic water column conditions, indicated, for example, by the generalised lack of enrichment in organic matter and redox metals typically associated with anoxia and euxinia. Carbon isotope stratigraphy (δ13CTOC) allowed to recognise the spinatum (=emaciatum in the Submediterranean Province), Pliensbachian-Toarcian, and early Toarcian Oceanic Anoxic Event negative carbon isotopic excursions and the late Pliensbachian positive carbon isotopic excursion. It is here suggested that the observed periodic changes in lithology and sedimentary geochemistry occur at orbital frequencies (i.e., long and short eccentricity and, tentatively, precession), hinting at an astronomical control of the local-regional climate and environment during the Pliensbachian and Toarcian in the mid-low latitude South Iberian palaeomargin area.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5473754

The trace fossil Dactyloidites ottoi (Geinitz, 1849) from the Neogene August Town Formation of south-central Jamaica

1993 ◽  
Vol 67 (6) ◽  
pp. 1070-1074 ◽  
Author(s):  
Ron K. Pickerill ◽  
Stephen K. Donovan ◽  
Harold L. Dixon
Keyword(s):  
Detailed Analysis ◽  
Trace Fossils ◽  
Trace Fossil ◽  
Marine Environments ◽  
Biogenic Origin ◽  
South Central ◽  
Rock Record ◽  
Distinctive Morphology ◽  
Detailed Interpretation ◽  
Deposit Feeding

Rosette-shaped problematica are relatively common structures in the Phanerozoic rock record. Historically, they have been accorded a variety of names and documented from various shallow to deep marine environments. Unfortunately, the detailed interpretation of many such structures as biogenic (trace fossils, medusoids, or other body fossils; see, for example, Häntzschel, 1970, 1975) or nonbiogenic (for example, Pickerill and Harris, 1979) in origin still remains to be resolved. However, a detailed analysis of one such structure by Fürsich and Bromley (1985), namely Dactyloidites Hall, 1886, convincingly demonstrated its biogenic origin. The distinctive morphology of Dactyloidites and its synonyms was interpreted by Fürsich and Bromley (1985) to result from successive probings of an essentially stationary deposit-feeding, worm-like organism, possibly possessing a proboscis, to produce a rosetted, vertical spreiten with a centrally located, vertical or subvertical shaft.

New ichnofabrics of the Cenomanian–Danian Chalk Group

2020 ◽  
Vol 90 (7) ◽  
pp. 701-712
Author(s):  
Kasper H. Blinkenberg ◽  
Bodil W. Lauridsen ◽  
Dirk Knaust ◽  
Lars Stemmerik
Keyword(s):  
Trace Fossils ◽  
Trace Fossil ◽  
Shelf Area ◽  
Fine Grained ◽  
Fossil Assemblages ◽  
Facies Types ◽  
Body Fossil ◽  
Substrate Hardness ◽  
Nw Europe ◽  
Different Levels

ABSTRACT The Cenomanian–Danian Chalk Group of NW Europe is characterized by distinct trace-fossil assemblages dominated by Thalassinoides isp., Planolites isp., Zoophycos isp., and Chondrites isp., whereas ichnogenera such as Taenidium and Phycosiphon are rare. The trace fossils form a complex tiering arrangement, which reflects burrowing activities of diverse benthic associations that operate at different levels in the sediment column, dynamic sedimentation rates, and changes in substrate hardness during progressive burial, forming intricate ichnofabrics. In the Danish Basin, studies of chalk ichnofabrics have focused mainly on the Maastrichtian. Studies of the shallower, grain-rich Danian chalk have revealed similar trace-fossil assemblages, whereas the ichnology of the fine-grained, deeper-water Danian deposits is poorly known. Based on detailed facies and ichnofabric analysis of a mid-Danian silica-rich, pelagic chalk located in the central, deeper shelf area of the Danish Basin, four facies types, eight ichnotaxa, and two ichnofabrics are recognized. Most conspicuous and abundant are randomly distributed, variously sized meniscate burrows attributed to Bichordites isp. and Taenidium isp., whereas other common chalk trace fossils are rare or absent. This trace-fossil assemblage outlines two new ichnofabrics in the NW European chalk, which are dominated principally by upper-tier traces. The producer of the abundant Bichordites isp. and Taenidium isp. burrows is identified as a sea urchin on the basis of an exceptionally preserved Bichordites isp. trace aligned with an irregular echinoid body fossil. The identified ichnofabrics controlled early silicification and produced a more complex distribution of silica concretions compared with chalk successions elsewhere. This results in volumetrically thick silica concretion-rich units rather than distinctive silica bands as seen in other Upper Cretaceous and Danian chalk units.

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