Hirnantia Fauna from the Condroz Inlier, Belgium: another case of a relict Ordovician shelly fauna in the Silurian?

2021 ◽  
pp. 1-27
Author(s):  
Sofia Pereira ◽  
Jorge Colmenar ◽  
Jan Mortier ◽  
Jan Vanmeirhaeghe ◽  
Jacques Verniers ◽  
...  
Keyword(s):  
Sea Level ◽  
Mass Extinction ◽  
Late Ordovician ◽  
Lake District ◽  
Low Diversity ◽  
Hirnantia Fauna ◽  
And Sea Level

Abstract The end-Ordovician mass extinction, linked to a major glaciation, led to deep changes in Hirnantian–Rhuddanian biotas. The Hirnantia Fauna, the first of two Hirnantian survival brachiopod-dominated communities, characterizes the lower–mid Hirnantian deposits globally, and its distribution is essential to understand how the extinction took place. In this paper, we describe, illustrate, and discuss the first macrofossiliferous Hirnantia Fauna assemblage from Belgium, occurring in the Tihange Member of the Fosses Formation at Tihange (Huy), within the Central Condroz Inlier. Six fossiliferous beds have yielded a low-diversity, brachiopod-dominated association. In addition to the brachiopods (Eostropheodonta hirnantensis, Plectothyrella crassicosta, Hirnantia sp., and Trucizetina? sp.), one trilobite (Mucronaspis sp.), four pelmatozoans (Xenocrinus sp., Cyclocharax [col.] paucicrenulatus, Conspectocrinus [col.] celticus, and Pentagonocyclicus [col.] sp.), three graptolites (Cystograptus ancestralis, Normalograptus normalis, and ?Metabolograptus sp.), together with indeterminate machaeridians and bryozoans were identified. The graptolite assemblage, from the Akidograptus ascensus-Parakidograptus acuminatus Biozone, indicates an early Rhuddanian (Silurian) age, and thus, an unexpectedly late occurrence of a typical Hirnantia Fauna. This Belgian association may represent an additional example of relict Hirnantia Fauna in the Silurian, sharing characteristics with the only other known from Rhuddanian rocks at Yewdale Beck (Lake District, England), although reworking has not been completely ruled out. The survival of these Hirnantian taxa into the Silurian might be linked to delayed post-glacial effects of rising temperature and sea-level, which may have favored the establishment of refugia in these two particular regions that were paleogeographically close during the Late Ordovician–early Silurian.

A silicified Hirnantia fauna (latest Ordovician brachiopods) from Guizhou, southwest China

1999 ◽  
Vol 73 (5) ◽  
pp. 831-849 ◽  
Author(s):  
Rong Jia-Yu ◽  
Li Rong-Yu
Keyword(s):  
Mass Extinction ◽  
Southwest China ◽  
The Other ◽  
Related Factors ◽  
Rugose Corals ◽  
Two New Species ◽  
Low Diversity ◽  
Generic Composition ◽  
Temperature Water ◽  
Hirnantia Fauna

A silicified brachiopod assemblage living between the first and second episodes of latest Ordovician mass extinction is first described from micritic bioclastic limestone of Kuanyinchiao Bed, northwestern Guizhou, southwest China. It contains six species, Dalmanella testudinaria (Dalman, 1828), Plectothyrella crassicosta (Dalman, 1828), Hindella crassa incipiens (Williams, 1951), Eostropheodonta sp., the characteristic constituents of the Hirnantia fauna, and two new species, Fardenia modica and Dorytreta longicrura. It lacks Hirnantia, Kinnella, Cliftonia, and Paromalomena, the other characteristic elements of the Hirnantia fauna. A new, low diversity community (inner BA3) dominated by brachiopods is proposed as the Dalmanella testudinaria-Dorytreta longicrura Community along with the trilobite Dalmanitina nanchengensis Lu, rugose corals, and gastropods. Composition of this community of the Hirnantia fauna was controlled primarily by temperature, water depth, and substrate. Comparison with other communities of the Hirnantia fauna in south China supports this conclusion. Fluctuations in generic composition of the Hirnantia fauna and the related factors are also discussed.

The development of an atypical Hirnantia-brachiopod Fauna and the onset of glaciation in the late Ordovician of Gondwana

2001 ◽  
Vol 92 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Owen E. Sutcliffe ◽  
David A. T. Harper ◽  
Abdallah Aït Salem ◽  
Robert J. Whittington ◽  
Jonathan Craig
Keyword(s):  
Continental Shelf ◽  
Sea Level ◽  
North Africa ◽  
Mass Extinction ◽  
Ice Sheet ◽  
Late Ordovician ◽  
Shallow Marine ◽  
Marine Deposits ◽  
Brachiopod Fauna ◽  
Glaciomarine Sediments

ABSTRACTThe development of an atypical Hirnantia Fauna in the late Ordovician of Gondwana was coeval with a slow eustatic fall induced by the abstraction of water into a growing ice sheet. This event is dated as early Hirnantian in age and occurred in tandem with the start of a major mass extinction. A tectonic episode in the Caradoc-Ashgill of North Africa differentiated the continental shelf into highs and lows and may have formed the land required for the accumulation of a permanent snow cover. Depositional lows were filled by regressive shallow-marine deposits in the early Hirnantian. During the mid-Hirnantian, advance and retreat of an ice sheet on the continental shelf resulted in the deposition of glaciomarine sediments above these regressive deposits. The demise of an atypical Hirnantia Fauna is attributed to deglaciation and the associated flooding of the continental shelf by a stratified anoxic water column. This glacioeustatic sea-level rise occurred in the late Hirnantian.

Late Ordovician mass extinction in the Selwyn Basin, northwestern Canada: geochemical, sedimentological, and paleontological evidence

1993 ◽  
Vol 30 (9) ◽  
pp. 1870-1880 ◽  
Author(s):  
K. Wang ◽  
B. D. E. Chatterton ◽  
M. Attrep Jr. ◽  
C. J. Orth
Keyword(s):  
Stable Isotope ◽  
Sea Level ◽  
Mass Extinction ◽  
Facies Analysis ◽  
Isotope Geochemistry ◽  
Late Ordovician ◽  
Cold Climate ◽  
Photic Zone ◽  
Toxic Material ◽  
Short Period

We present a detailed study of the trace element and stable isotope geochemistry, sedimentology, and fossil distributions in two Avalanche Lake (AV4B, AV1) Ordovician–Silurian boundary sections in the Selwyn Basin. Trilobites and conodonts indicate a profound extinction at the end of the Ordovician, which is constrained stratigraphically within a <60 cm interval at AV4B. Facies analysis suggests that the extinction interval coincides with the maximum shallowing (low stand of sea level), which was probably caused by a galcioeustatic regression induced by the Late Ordovician Gondwanan glaciation. The extinction crisis is also signalled by the change in carbonate δ13C: a sudden "Strangelove ocean" δ13C excursion (>3‰ in magnitude) is recorded in the extinction interval. Iridium abundances (<0.051 ppb) in the extinction interval are low and fail to provide evidence for an impact. The highest Ir abundance is found to be associated with reduced sedimentation in a condensed horizon. Cerium anomalies indicate a short period of basin ventilation in the otherwise anoxic Selwyn Basin. The extinction occurred during the time of this basin ventilation, which was probably caused by the cold climate during the glaciation. The ventilation may have triggered upwelling of the deep water through vertical advection, bringing up toxic material, poisoning the upper-water photic zone, and causing the extinction.

Brachiopod Synecology in a Time of Crisis (Late Ordovician-Early Silurian)

Paleobiology ◽  
1975 ◽  
Vol 1 (2) ◽  
pp. 205-212 ◽  
Author(s):  
Peter M. Sheehan
Keyword(s):  
North America ◽  
Sea Level ◽  
North American ◽  
Late Ordovician ◽  
North American Species ◽  
European Species ◽  
Geologic Time ◽  
Stable Conditions ◽  
Low Diversity ◽  
Shallow Seas

The extinction of endemic brachiopods in North America at the end of the Ordovician and recolonization by European species has been related to glacio-eustatic lowering of sea level which disrupted conditions in epicontinental seas. North American species may have been narrowly adapted to relatively stable conditions of broad, tropical shallow seas. European invaders may have been less specialized because they were adapted to conditions in both the open ocean and in narrow European epicontinental seas. Being less narrowly adapted, European species probably were better able to cope with changing environmental conditions than were North American species.During the Lower and Middle Llandovery, shallow water, low diversity communities of Pentamerus Community depth were unstable and characterized by repeated extinctions and invasions. Following the crisis at the Ordovician-Silurian boundary 3 to 5 million years were needed to reestablish communities that were persistent in geologic time.

First record of a Hirnantia Fauna from Spain, and its contribution to the Late Ordovician palaeogeography of northern Gondwana

1998 ◽  
Vol 89 (3) ◽  
pp. 187-197 ◽  
Author(s):  
E. Villas ◽  
S. Lorenzo ◽  
J. C. Gutiérrez-Marco
Keyword(s):  
Regional Development ◽  
Iberian Peninsula ◽  
First Record ◽  
Late Ordovician ◽  
Carnic Alps ◽  
Ciudad Real ◽  
Low Diversity ◽  
Brachiopod Fauna ◽  
Armorican Massif ◽  
Hirnantia Fauna

AbstractA new occurrence of the Hirnantia brachiopod fauna is documented from the Criadero Quartzite of Almadén, Ciudad Real Province, Spain. This unit is the regional development of a largely unfossiliferous sandy facies that frequently overlies the typical Late Ordovician diamictitic glaciomarine formations in the Iberian Peninsula and the Armorican Massif. The new occurrence establishes palaeontologically the latest Ashgill age of the quartzite, at least for its lowest horizons, and adds new data on a fauna that, although widespread, has been very rarely documented from peri-Gondwanan Europe. The new collection contains only Hirnantia sagittifera and Plectothyrella crassicosta chauveli. The subspecific status of the latter and its inclusion within Plectothyrella crassicosta is discussed herein, based on the continuous variation in rib thickness of several samples of both forms. The extremely low diversity and the occurrence of the key form P. c. chauveli, are both typical of the Bani Province that developed on the subpolar margins of Gondwana. This contrasts with other occurrences of the Hirnantia Fauna in peri-Gondwanan Europe, such as those from Sardinia and the Carnic Alps, which are characteristic of the more temperate Kosov Province.

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