Ostracods from Upper Ordovician (Katian) carbonate lithofacies in southwest Scotland

Abstract

The Ordovician Craighead Limestone Formation of southwest Scotland was formed on a carbonate platform on the eastern tropical margin of the Laurentia palaeocontinent during the early Katian (c. 456 Ma). It yields the most diverse and well-preserved ostracod fauna yet recovered from the Scottish Ordovician succession, with some 25 species divisible into two distinct marine biotopes comprising shallow lagoonal and deeper platform margin settings, respectively. The ostracods show strong biogeographic links at species-level with Sandbian and early Katian faunas of North America, including Krausella arcuata, Steusloffina cuneata, Monoceratella teres and species of Levisulculus and Platybolbina. However, many of the ostracod genera that characterize the Craighead Limestone Formation have earlier origins in the Baltica palaeocontinent, suggesting enhanced migration of species from mid- (Baltica about 30° S) to low (Laurentia) latitudes in the late Sandbian and early Katian interval. Such Baltica-origin genera include Distobolbina, Kiesowia and Platybolbina. Notable is the wide biogeographic occurrence of Steusloffina cuneata, extending from warm tropical Laurentia to cooler high-latitude Gondwana, an enormous latitudinal range for a shelf-dwelling marine species. The possible Tvaerenellidae taxon Duoarcus levigatus gen. et sp. nov. is described.

Cephalopods from reef limestone of the Vasalemma Formation, northern Estonia (latest Sandbian, Upper Ordovician) and the establishment of a local warm-water fauna

“…The cephalopod assemblage from the Vasalemma Formation tells a different story, because most of the genera known from the Vasalemma Formation have their first record on Baltica, and/or the South and North China cratons and migrated only during the Katian towards Laurentia. A similar early Katian immigration trend toward Laurentia was recognised also for ostracods (Mohibullah et al 2010). The cephalopod migration pattern indicates that the northward shift of Baltica and the the concomitant closing of the Iapetus Ocean during the Mid-Late Ordovician caused not a one-way immigration route but affected the Late Ordovican faunas of Laurentia and Baltica alike.…”

Marine Ostracod Provinciality in the Late Ordovician of Palaeocontinental Laurentia and Its Environmental and Geographical Expression

“…In previous studies of Late Ordovician ostracods water depth has been considered to have a strong influence on the distribution of ostracods [17] , [20] , [67] . Thus, the two biofacies in the lower Esbataottine Formation of the Mackenzie district, Canada, are interpreted as a deeper platform biofacies and a shallow shelf biofacies that also has some elements extending into deeper shelf facies [17] .…”

“…They argued that faunal similarity from the Middle to Late Ordovician was indicative of a narrowing Iapetus Ocean and the ability of some species to migrate across this ocean. By Late Ordovician times, there were early species-level links between Laurentia, Baltica and Avalonia [46] , [57] , [67] .…”

“…By the early Late Ordovician ( bicornis Biozone) both the Marginal province faunas and the Midcontinent Province faunas possessed generic links with Baltica [14] and Avalonia (this study). Thereafter, the Marginal Province faunas produced the first species-level links with Baltica and Avalonia during the Late Ordovician [57] , [67] , [73] . Many species ( Longiscula perfecta , L. tersa , Medianella longa , Steusloffina cuneata and species of Hemiaechminoides and Kinnekullea ) that are restricted to the Marginal Province of Laurentia are also present in the early Katian of the Baltic region ( Figure 5 ; [67] .…”

Importance of Dimorphosiphon (Chlorophyta, Bryopsidales) for Facies and Paleobiogeographic Studies of the Upper Ordovician Richmondian Red River Formation, Williston Basin

“…4-5) described Dimorphosiphon rectangulare from the Girvanella-and Solenopora-rich Craighead Limestone (Upper Ordovician, Caradocian) of the Girvan area of Scotland. Green algae dominate in low-energy lagoonal facies and were subordinate in high-energy shoals (Mohibullah et al, 2010). The Craighead Limestone is of lower Katian age (mid-Caradocian), based on the occurrence of graptolites (Dicranograptus clingani Biozone, caudatus Subzone: Tripp, 1980;Williams & Floyd, 2000), shelly fauna (Ingham, 1992;Leslie and Bergström, 1995), conodonts (low level within the Amorphognathus superbus Biozone: Bergström, 1990), and ostracodes (Williams & Floyd, 2000;Mohibullah et al, 2010).…”