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8 Upper Ordovician bioerosion structures . ( a ) Trypanites weisi ( cross-sectional view ) in a carbonate hardground. Katian, Grant Lake Limestone, near Washington, Kentucky, USA; ( b ) Trypanites weisi ( bedding-plane view ) in a carbonate hardground. Katian, Grant Lake Limestone, near Manchester, Ohio, USA; ( c ) Palaeosabella isp. in a trepostome bryozoan. Katian, Whitewater Formation, near Richmond, Indiana, USA; ( d ) Petroxestes pera . Katian, Whitewater Formation, Caesar Creek Lake emergency spillway, near Waynesville, Ohio, USA; ( e ) Ropalonaria venosa in a strophomenid brachiopod. Katian, Liberty Formation near Brookville, Indiana, USA
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The Global Ordovician Biodiversification Event (GOBE) was undoubtedly one of the most significant evolutionary events in the history of the marine biosphere. A continuous increase in ichnodiversity occurs through the Ordovician in both shallow- and deep-marine environments. The earlier view that early Paleozoic deep-marine ichnofaunas are of low al...
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... Evidence of biology (e.g. trace fossils) can be found in ancient channels (Cummings & Hodgson, 2011;Mángano et al., 2016). However, this record might be preservationbiased towards either hard-bodied organisms or certain types of soft-bodied organisms, rather than say the tubeliving organisms in this study. ...
Submarine channels are key features for the transport of flow and nutrients into deep water. Previous studies of their morphology and channel evolution have treated these systems as abiotic, and therefore assume that physical processes are solely responsible for morphological development. Here, a unique dataset is utilised that includes spatial measurements around a channel bend that hosts active sediment gravity flows. The data include flow velocity and density, alongside bed grain size and channel‐floor benthic macrofauna. Analysis of these parameters demonstrate that while physical processes control the broadest scale variations in sedimentation around and across the channel, benthic biology plays a critical role in stabilising sediment and trapping fines. This leads to much broader mixed grain sizes than would be expected from purely abiotic sedimentation, and the maintenance of sediment beds in positions where all the sediment should be actively migrating. Given that previous work has also shown that submarine channels can be biological hotspots, then the present study suggests that benthic biology probably plays a key role in channel morphology and evolution, and that these need to be considered both in the modern and when considering examples preserved in the rock record.
... The finding of Lingulichnus in direct association with its producer has implications to unravel the early colonization of the deep sea. Whereas Cambrian deep-marine deposits are dominated by trace fossils reflecting the exploitation of microbial mats, Ordovician base of slope and basinal deposits show the appearance of ichnofaunas that are ethologically closer to those typical of the modern deep sea 58,60,[123][124][125][126][127] . In this sense, a progressive increase in the proportion of farming and trapping structures with respect to those produced by deposit and detritus feeders is apparent through the Ordovician. ...
Trace fossils from Ordovician deep-marine environments are typically produced by a shallow endobenthos adapted to live under conditions of food scarcity by means of specialized grazing, farming, and trapping strategies, preserved in low-energy intermediate to distal zones of turbidite systems. High-energy proximal zones have been considered essentially barren in the early Paleozoic. We report here the first trace and body fossils of lingulide brachiopods in deep-marine environments from an Upper Ordovician turbidite channel-overbank complex in Asturias, Spain. Body and trace fossils are directly associated, supporting the interpretation of a lingulide tracemaker. Ellipsoidal cross-section, cone-in-cone spreite, and spade morphologies suggest the specimens belong to Lingulichnus verticalis. The oblique orientation in both trace and body fossils is the result of tectonic deformation. The organisms were suspension feeders showing escape, dwelling, and equilibrium behaviours controlled by sedimentation rates associated with turbidite deposition. These trace fossils and their in situ producers represent the oldest evidence of widespread endobenthos colonization in high-energy, proximal areas of turbidite systems, expanding the bathymetric range of Lingulichnus and the variety of behaviours and feeding styles in early Paleozoic deep-marine environments.
... The thick calcitic skeletons of Ordovician trepostome bryozoans were prominent substrates for bioeroding organisms, especially worm-like excavators of tubular macroborings and bioeroding bivalves (Wilson 2007, Wyse Jackson & Key 2007, Vinn et al. 2019. Ordovician bryozoans, in fact, record a dramatic increase in boring intensity and diversity known as the Ordovician Bioerosion Revolution (Wilson & Palmer 2006, Mángano et al. 2016. Because Ordovician trepostomes are often large and hemispherical, they can have borings that develop internally in three dimensions. ...
Non-destructive 3D imaging technology is used to determine if it can aid taxonomic
identification of Palaeozoic palaeostome bryozoans. In previous studies it has not proved very successful with calcified specimens because the density contrast between the walls and zooecial infill is too weak to resolve the interior details. However, X-ray Micro Computed Tomography (X-ray µCT) and Microscopy (XRM) can be valuable in other ways and here we present two case studies. The interiors of extremely small, silicified Silurian fenestrate colonies have been visualised enabling us to create ‘digital thin sections’ at resolutions (voxel sizes) between 2.75 and 8.47 µm. The same technique can be used to gain a greater understanding of the borings common in Ordovician bryozoans, enabling construction of a 3D image of the structures
produced
... The thick calcitic skeletons of Ordovician trepostome bryozoans were prominent substrates for bioeroding organisms, especially worm-like excavators of tubular macroborings and bioeroding bivalves (Wilson 2007, Wyse Jackson & Key 2007, Vinn et al. 2019. Ordovician bryozoans, in fact, record a dramatic increase in boring intensity and diversity known as the Ordovician Bioerosion Revolution (Wilson & Palmer 2006, Mángano et al. 2016. Because Ordovician trepostomes are often large and hemispherical, they can have borings that develop internally in three dimensions. ...
... The Great Ordovician Biodiversification Event (GOBE) evidenced one of the most important transformations in carbonate endobenthic communities. Besides increasing ichodisparity and global ichnodiversity, it includes depth of bioturbation reaching 1 m-depth (Droser & Bottjer 1989;Mángano et al. 2016). The latter is attributed to a switch in dominance from shallow three-dimensional tunnel systems (networks) to deep and complex open galleries (boxworks) (Droser & Bottjer 1989;Myrow 1995). ...
The Agronomic Revolution implies a gradual sophistication of organism-substrate interactions and progressive colonization of shelf environments by vagile endobenthos in the late Ediacaran and Cambrian periods. These changes are impressively mirrored in a palaeontological record of ichnoassemblages in marine siliciclastic facies. In con-trast, endobenthic communities in carbonate successions remained comparatively poor until a fundamental transformation during the Great Ordovician Biodiversification Event. Herein we report complex open burrows (Thalassinoides and Olenichnus) from the Sukharikha Formation exposed near the Plakhinskii Island (Yenisei River, Igarka Uplift). Lithological and chemostratigraphical correlation with the stratotype suggest the Terreneuvian age of the fossil-bearing strata accumulated in storm-agitated mid- to dis-tal inner-ramp settings. Each of the ichnotaxa occurs in a specific deposit in the studied section: Olenichnus is localised exclusively in the background-sedimentation deposits, whereas Thalassinoides occurs in the storm-event beds. Our data support early reports suggesting that colonization of marine carbonate sediments by burrowing metazoans was initiated already in the Terreneuvian and became a solid basis for the following development of deep-tier bioturbation in carbonates in the Ordovician Period.
... It was one of the most intense periods of Phanerozoic volcanism (Parnell and Foster, 2012), preserving numerous volcanics (including volcanic rocks and volcaniclastic deposits; Fig. 1A). The Great Ordovician Biodiversification Event was another 'explosion' of life after the Cambrian Explosion (Mángano et al., 2016). The first of the big five Phanerozoic mass extinctions, the Late Ordovician Mass Extinction, interrupted the increase of biodiversity in this period (Sheehan, 2001). ...
The origin and evolution of land plants in the Ordovician and Carboniferous reshaped the terrestrial environment, marine ecology, and atmospheric composition, ultimately triggering global climate change. Phosphorus (P) is a limiting nutrient for plants and can only be obtained from pedogenic weathering of bedrock (including rocks and deposits). In the Ordovician and Carboniferous, periodic and frequent volcanic eruptions at convergent plate margins formed the bedrock that elevated P supply for the terrestrial biosphere. Temporal variation of P availability reveals that volcanic P supply spiked at 474–465 Ma, 454–445 Ma, and 319–310 Ma, with the assembly of Gondwana and Pangaea supercontinents. The abundant P supported the crucial Phanerozoic ecological transitions marked by the episodically increased land plant biomass and emergence of non-vascular, vascular, and seed plants. The volcanism-driven evolution and expansion of land plants further accelerated rock weathering and enhanced organic carbon burial. This positive feedback eventually resulted in the ice ages in the Paleozoic. Therefore, the variation of P availability, dependent on the scale and P content of volcanic products, was strongly associated with the plate subduction during supercontinent assembly, revealing the significant impact of tectonism on terrestrial ecosystems.
... The thick calcitic skeletons of Ordovician trepostome bryozoans were prominent substrates for bioeroding organisms, especially worm-like excavators of tubular macroborings and bioeroding bivalves (Wilson 2007, Wyse Jackson & Key 2007, Vinn et al. 2019. Ordovician bryozoans, in fact, record a dramatic increase in boring intensity and diversity known as the Ordovician Bioerosion Revolution (Wilson & Palmer 2006, Mángano et al. 2016. Because Ordovician trepostomes are often large and hemispherical, they can have borings that develop internally in three dimensions. ...
... The combination of increased diversity and BSI values may have contributed to bryozoans being the most diverse group of reef-building organisms during the GOBE (Ernst 2018;Servais and Harper 2018). The Ordovician diversification of trepostomes was a component of the GOBE (Taylor and Larwood 1990;Taylor and Ernst 2004), including as a substrate for the Ordovician Bioerosion Revolution (Mángano et al. 2016). The lack of change from the Calcite I Sea into the Aragonite II Sea suggests that the trepostomes were accommodating the change in seawater chemistry in some other way. ...
Trepostome bryozoan skeletalisation did not passively respond to changes in seawater chemistry associated with calcite-aragonite seas. According to Stanley and others, trepostome bryozoans were passive hypercalcifiers. However, if this was the case, we would expect their degree of calcitic colony calcification to have decreased across the Calcite I Sea to the Aragonite II Sea at its transition in the Middle Mississippian. Data from the type species of all 184 trepostome genera from the Early Ordovician to the Late Triassic were utilised to calculate the Bryozoan Skeletal Index (BSI) as a proxy for the degree of calcification. BSI values and genus-level diversity did not decrease across the transition from the Calcite I Sea to the Aragonite II Sea. Nor were there any changes in the number of genus originations and extinctions. This suggests that trepostome bryozoans were not passive hypercalcifiers but active biomineralisers that controlled the mineralogy and robustness of their skeletons regardless of changes in seawater chemistry.
... A gradual increase in ichnodiversity and infaunalization in both shallow-and deep-sea environments accompanied by increased vertical partitioning of the infaunal and epifaunal communities (tiering) occurred after the 'Cambrian agronomic revolution' (Seilacher & Pflüger 1994;Mángano & Buatois 2017), but with a considerable acceleration during the Great Ordovician Biodiversification Event (GOBE; Mángano & Droser 2004;Mángano et al. 2016;Servais & Harper 2018). As a result, progressive ecospace utilization by deposit and detritus-feeding producers of burrows, such as Treptichnus, Trichophycus, Teichichnus, Rosselia, Daedalus, Arthrophycus and Phycodes, can be observed in open marine settings (Seilacher 2000;Mángano et al. 2016). ...
... A gradual increase in ichnodiversity and infaunalization in both shallow-and deep-sea environments accompanied by increased vertical partitioning of the infaunal and epifaunal communities (tiering) occurred after the 'Cambrian agronomic revolution' (Seilacher & Pflüger 1994;Mángano & Buatois 2017), but with a considerable acceleration during the Great Ordovician Biodiversification Event (GOBE; Mángano & Droser 2004;Mángano et al. 2016;Servais & Harper 2018). As a result, progressive ecospace utilization by deposit and detritus-feeding producers of burrows, such as Treptichnus, Trichophycus, Teichichnus, Rosselia, Daedalus, Arthrophycus and Phycodes, can be observed in open marine settings (Seilacher 2000;Mángano et al. 2016). This is manifested by the increase in sediment mixing especially in offshore areas . ...
... This is manifested by the increase in sediment mixing especially in offshore areas . Together with body fossils, ichnological studies may help in deciphering the palaeoecological revolution of the GOBE and in obtaining considerable information on the ethology (the behavioural classification), habitats of the producer, ecospace utilization, tiering pattern and onshore-offshore trends (McIlroy & Logan 1999;Mángano & Droser 2004;Mángano et al. 2016). In this context, Trichophycus is one of the ichnotaxa that contributed to the exploitation of infaunal ecospace in offshore settings where it increased the disruption of the primary sedimentary fabric and formed the 'three-dimensional Trichophycus ichnofabrics' Shallow-marine siliciclastic deposits of the Shirgesht Formation (the Tremadocian-to-Floian members 1, 2) are composed of stacked offshore-toforeshore shallowing-upward cycles (Figs 1, 2), which include barrier-island to shoreface-offshore facies and contain diverse trace fossils of various ethologies (Bayet-Goll et al. 2016). ...
The Tremadocian‐to‐Floian siliciclastic deposits of the Shirgesht Formation in the Kalmard Block of central Iran show abundant occurrences of the mid‐tier Trichophycus venosus, a common ichnotaxon in the archetypical Cruziana ichnofacies. This trace fossil records a considerable increase in exploitation of offshore infaunal ecospace in comparison with older formations. Here, Trichophycus is relatively long and wide, with numerous and deep successively stacked causative burrows, which form dense burrow systems building the Crowded Trichophycus ichnofabric (CTI). Such development of CTI and the increase in depth of bioturbation had a negative effect on preservation of shallow‐tier traces, for example arthropod burrows and trackways. This resulted in decreasing abundance of trilobite‐produced trace fossils towards the top of the succession. The palaeobiological and palaeoecological interpretation of CTI points to stable habitats in muddy substrates above the storm wave base with high content of food and oxygen in pore waters, low‐energy hydrodynamic regimes and a long colonization window. Moreover, the architecture and the morphological features of Trichophycus suggest a combined dwelling‐feeding activity of the resident fair‐weather producer showing the K‐selected/climax strategy. The ethology of the producer, palaeoecological interpretations and taphonomic signatures revealed that it preferred dewatered, compacted muddy substrates (firmgrounds) in offshore settings, which might be related to minor hiatuses or short‐lived discontinuities. Although the appearance of Trichophycus is concomitant to the earliest Cambrian agronomic revolution, it was uncommon until the early Ordovician, when locally it records infaunalization related to the Great Ordovician Biodiversification Event.
... A key question is whether the modern seafloor is a good analogue for sediment over geological time, and thus whether these variations with depth are typical. The level and type of bioturbation in deep-sea substrates experienced a major change during the Great Ordovician Biodiversification event (Orr, 2001;M angano et al., 2016;Buatois & M angano, 2018). Since the Ordovician, the diversity of deep-sea trace fossils has fluctuatedoften related to large-scale changes in ocean circulation and oxygenation, such as basinscale anoxic eventsand some ichnotaxa, such as Zoophycos and Ophiomorpha, have changed their environmental range (e.g. ...
Flutes and tool marks are commonly observed sedimentary structures on the bases of sandstones in deep‐water successions. These sole structures are universally used as palaeocurrent indicators but, in sharp contrast to most sedimentary structures, they are not used in palaeohydraulic reconstructions or to aid prediction of the spatial distribution of sediments. Since Kuenen’s famous 1953 paper, flutes and tool marks in deep‐water systems have been linked to turbidity currents, as reflected in the standard Bouma sequence taught to generations of geologists. Yet, these structures present a series of unaddressed enigmas. Detailed field studies in the 1960s and early 1970s observed that flutes are typically associated with thicker, more proximal beds, whilst tools are generally prevalent in thinner, more distal, beds. Additionally, flutes and tool marks are rarely observed on the same surfaces, and flutes are seen to change downstream from larger wider parabolic to smaller narrower spindle shaped forms. No model has been proposed that explains these field‐based observations. This contribution undertakes a radical re‐examination of the formative flow conditions of flutes and tool marks, and demonstrates that they are the products of a wide range of sediment gravity flows, from turbulent flows, through transitional clay‐rich flows, to debris flows. Flutes are not solely the product of turbulent flows, but can continue to form in transitional flows. Grooves are shown to be formed by debris flows, slumps and slides, not turbidity currents, and in many cases the debris flows are linked to the debritic component of hybrid flows. Discontinuous tool marks, including skim (bounce) marks, prod marks and skip marks, are shown to be formed by transitional mud‐rich flows. Consequently, the observed spatial distribution of flutes and tool marks can be explained by a progressive increase in flow cohesivity downstream. This model of flutes and tool marks dovetails with models of hybrid flows that predict such a longitudinal increase in flow cohesivity. However, some deposits show grooves preferentially associated with Bouma TA beds, and these are likely formed by flows transforming from higher to lower cohesion, and are present in basins where hybrid beds are absent or rare. The recognition that sole structures may have no genetic link to the later overlying turbidity current deposits, and can be formed by a wide range of flow types, indicates that the existing pictorial description of the Bouma sequence is incorrect. A modified Bouma sequence is proposed here that addresses these points. In utilizing the advances in fluid dynamics since Kuenen’s pioneering research, this study demonstrates that it is possible to use flutes and tool marks to interpret flow type at the point of formation, the nature of flow transformations, and the mechanics of the basal layer. These advances suggest that it is then possible to predict the nature of deposit type down‐dip. This new understanding, in combination with further testing in outcrop of the proposed relationships between sole marks and palaeohydraulics, opens up a wealth of possibilities for improving the understanding of deep‐water clastic environments, with implications for developing more complete facies models, assessing subaqueous geohazards and the resilience of seafloor infrastructure, and advancing our understanding of deep‐water sediments as archives of palaeoenvironmental change.
