Liam G Herringshaw | University of Hull (original) (raw)

Papers by Liam G Herringshaw

Zoological Journal of the Linnean Society

The genus Cornulites , with the type species C. serpularius Schlotheim, 1820, from the Silurian o... more The genus Cornulites , with the type species C. serpularius Schlotheim, 1820, from the Silurian of Gotland, comprises annulated, conical or tubular calcite shells, often found attached to the hard parts of other organisms. No consensus has ever been reached over the zoological affinities of the taxon, and no examples of soft-part preservation are known: detailed examination of shell structures and growth patterns provide the only means of assessing its systematic position. Using transverse and longitudinal thin sections of C. serpularius Vine, 1882, and C. cellulosus sp. nov. , from the Much Wenlock Limestone Formation of England, the shell structure of Cornulites is shown to be lamellar, but with conspicuous internal chambers (camerae) at the apical end of the shell and, particularly in C. cellulosus , numerous smaller vacuities (cellulae) between the lamellae in the apertural shell region. Growth of the shell was by the secretion of low-magnesian calcite increments within one another, giving a cone-in-cone structure, with the prominent development of cellulae in C. cellulosus probably a constructional feature relating to an upright life position. By comparison of morphology and shell structure with other taxa, the zoological affinities of Cornulites are re-examined; previously suggested affinities with annelids, foraminifers, molluscs and poriferans can be ruled out. Specific shell structures, most notably pseudopuncta similar to those of bryozoans and brachiopods, have led some recent workers to interpret cornulitids as lophophorates. However, it is shown that they can be interpreted alternatively as solitary, aseptate members of the stem-Zoantharia (Cnidaria: Anthozoa). Four cornulitid species are recognized in the Much Wenlock Limestone Formation: C. cellulosus sp. nov. , C. gremialis sp. nov. , C. scalariformis and C. serpularius . In the absence of the type material, C. serpularius is here restricted to cornulitids closely resembling the specimens originally figured by Schlotheim.

ABSTRACT Regularly-spaced arrays of opening-mode fractures develop in brittle layers (sandstone, ... more ABSTRACT Regularly-spaced arrays of opening-mode fractures develop in brittle layers (sandstone, limestone) that are embedded within a weaker matrix (shale) and subjected to layer-parallel extension. Where cut by tectonic faults, such brittle layers display a range of features including drag folds, shear fractures and rotated blocks, in addition to opening-mode fractures. In both cases, the weaker matrix deforms in a macroscopically ductile manner. Knowledge of the "mechanical stratigraphy" can therefore aid fracture prediction in subsurface reservoirs. A key question for unconventional hydrocarbon exploration is to what extent does the concept of mechanical stratigraphy apply to thick, shale-dominated sequences? The Toarcian (Lower Jurassic) Whitby Mudstone Formation (WMF) is a ca. 105 m thick, shale-dominated sequence that crops out within the Cleveland Basin, NE England and was deposited in < 7.4 Myr. The WMF contains both black and grey shale intervals. The lowermost Mulgrave Shale Member ("Jet Rock"; Harpoceras falciferum Zone, Cleviceras exaratum Subzone) of the WMF is characterised by high total organic carbon (TOC < 18 %), but low SiO2, Al2O3 and K2O. TOC decreases, but SiO2, Al2O3 and K2O all increase above the exaratum Subzone ("Bituminous Shales"). These geochemical variations are consistent with an upward increase in quartz and clay content within the Mulgrave Shale Member. The upper part of the Alum Shale Member ("Cement Shales"; Hildoceras bifrons Zone, Zugodactylites braunianus Subzone) is characterised by low TOC, Al2O3 and K2O, but high SiO2 consistent with a high quartz and low clay content. The Jet Rock and Bituminous Shales are cut by regularly-spaced arrays of sub-vertical, calcite-filled opening-mode fractures that abut against sub-horizontal, bedding-parallel fractures with ca. 1 m vertical spacing. By contrast, the Cement Shales are characterised by arrays of dipping (dip < 60° ) shear fractures with consistent extensional offsets. We hypothesise that large fluid overpressures (? ? 1) generated during clay diagenesis and/or kerogen maturation within the highly stratified (i.e. mechanically isotropic) Mulgrave Shale Member contributed to the development of bedding-parallel veins within the Jet Rock and Bituminous Shale. More speculatively, the spacing of the bedding-parallel veins may be controlled by metre- and sub-metre scale variations in organic and/or clay content throughout the Mulgrave Shale Member, which in turn may reflect primary sedimentary discontinuities. The regular spacing of compositional variations and discontinuity surfaces is likely to be a consequence of allogenic forcing mechanisms. By contrast, the SiO2-rich, TOC- and clay-poor Cement Shales appear to be compositionally more homogeneous. The Cement Shales deformed under conditions of higher effective normal stress (? < 1), giving rise to shear fractures with classic Andersonian geometries. Our observations suggest that stratigraphy exerts a strong control on fracturing within thick, shale-dominated sequences. However, the relationship between "mechanical stratigraphy" and fracture spacing and orientation appears to be more complex than in conventional clastic reservoir sequences.

Palaeogeography, Palaeoclimatology, Palaeoecology, 2015

AAPG Bulletin, 2014

ABSTRACT Faults and fractures within the well-exposed Lower Jurassic Cleveland Ironstone and Whit... more ABSTRACT Faults and fractures within the well-exposed Lower Jurassic Cleveland Ironstone and Whitby Mudstone Formations may provide insights into the tectonic history of gas-prospective, Mississippian shale in northern England. Subvertical opening mode fractures occur throughout the Cleveland Basin. Bed-parallel fractures, some of which contain blocky calcite fills, occur preferentially within well-bedded, clay-rich mudstones of the Cleveland Ironstone and Whitby Mudstone Formations at Jet Wyke and Port Mulgrave. Subvertical fractures display abutting or curving-parallel relationships with under- and overlying bed-parallel fractures. Together, these observations suggest that bed-parallel fractures, at times, acted as free surfaces. Some bed-parallel fractures curve toward and branch from calcite-filled fault slip surfaces, indicating that bed-parallel fracturing and normal faulting were synchronous, occurring within a regional stress field with vertical maximum principal stress. This apparent paradox can be explained by normal compaction, followed by cementation and coupling between pore pressure and minimum horizontal stress driven by poroelastic deformation or incipient slip along critically stressed normal faults, causing elevation of horizontal stress in excess of the vertical stress within clay-rich units. Propagation of bed-parallel fractures was enhanced by dilatational strains adjacent to normal fault planes. Bed-parallel fractures have not been observed within more Formula -rich units at the top of the Whitby Mudstone Formation at Whitby East Cliff, or within well-bedded, clay-rich shale at Saltwick Nab. This observation is consistent with the lack of normal faulting at Saltwick Nab, and the Whitby Mudstone Formation having been drained by structural and/or stratigraphical juxtaposition against permeable Middle Jurassic sandstones at both these localities.

This fieldtrip will introduce you to the late Ediacaran paleobiology and ichnology of Newfoundlan... more This fieldtrip will introduce you to the late Ediacaran paleobiology and ichnology of Newfoundland, and will touch upon some of the most interesting current debates and research areas in this field. Newfoundland contains some of the world’s best exposures of latest Neoproterozoic sedimentary successions. Although Cryogenian and early Ediacaran sedimentary units are not exposed in Newfoundland, deposits relating to the Gaskiers glaciation (considered by some to represent the final ‘Snowball Earth’ event), and extensive late Ediacaran fossil-bearing units, are well displayed and have been the subject of extensive study sciences in Canada and the world.

Data from around the world (and the USA) show that more than four million onshore hydrocarbon wel... more Data from around the world (and the USA) show that more than four million onshore hydrocarbon wells have been drilled globally.

Journal of Sedimentary Research, Jun 2013

Palaios, 2010

Modification of event beds by the burrowing nereidid polychaete Alitta virens (Sars) was examined... more Modification of event beds by the burrowing nereidid polychaete Alitta virens (Sars) was examined using laboratory microcosms, to assess its importance as an ecosystem engineer in pristine sediments. In all microcosms, the nereidids modified their environment to permit longterm occupation, but different behavioral strategies and burrow morphologies were observed based on sediment characteristics and nutrient availability. Alitta virens utilized scavenging, surface deposit feeding, suspension feeding, microbial gardening, deposit feeding at depth, and cannibalism. Suspension feeding using mucus nets is used by many nereidids but has not been documented previously in A. virens; extended use of the technique may indicate low availability of biotic sediments for deposit feeding. Alitta virens typically produced burrows similar to Arenicolites and Skolithos, but morphologies resembling Polykladichnus, Planolites, Palaeophycus, and Thalassinoides were formed under differing sedimentary conditions and over different time scales. In the rock record, such ichnological diversity might be interpreted as indicating paleoecological diversity, rather than the response of one taxon to changing conditions. Alitta virens is an allogenic ecosystem engineer, its behavior changing the physical and geochemical characters of its environment. These changes, combined with the widespread occurrence and population longevity of A. virens, demonstrate that burrowing polychaetes are important ecosystem engineers in shallow marine environments, and are likely to have been so over geological time scales.

Aquatic Biology, Jun 2008

The Ordovician-Silurian succession of the Llandovery area, mid-Wales, preserves shallow marine se... more The Ordovician-Silurian succession of the Llandovery area, mid-Wales, preserves shallow marine sediments deposited during the Hirnantian (end-Ordovician) extinction event. Ichnological analysis of the rocks shows that the degree and depth of bioturbation in this part of the Welsh Basin was often low across this interval, both during glacioeustatic sea level fall and the early part of the subsequent transgression. This pattern suggests that stratigraphic dilution was not the primary control on trace fossil abundance: an increase in sediment supply during the regression could explain low abundance in early Hirnantian units, but not in the post-glacial transgressive strata. A significant decrease in oxygen levels during sea level rise might be invoked instead, but this cannot have been the sole cause, as the occurrence of burrows up to 20 mm in diameter in the Bronydd Formation (late Hirnantian-Rhuddanian) shows that seafloor oxygen levels were at least intermittently high. An absence of vertical bioturbation through much of the succession indicates that sessile, suspensionfeeding organisms were generally scarce. The overall pattern probably reflects a decline in benthic infauna during the extinction event, but the 2 pulses of extinction described previously in body fossils are not evident ichnologically in this part of the Welsh Basin.

Aquatic Biology, 2010

Herringshaw LG, Solan M Benthic bioturbation in the past, present and future ………………………………………………… ... more Herringshaw LG, Solan M Benthic bioturbation in the past, present and future ………………………………………………… 201-205 Teal LR, Bulling MT, Parker ER, Solan M Global patterns of bioturbation intensity and mixed depth of marine soft sediments ……………… 207-218 Maire O, Lecroart P, Meysman F, Rosenberg R, Duchêne JC, Grémare A Quantification of sediment reworking rates in bioturbation research: a review ……………………… 219-238 Meysman FJR, Malyuga VS, Boudreau BP, Middelburg JJ Quantifying particle dispersal in aquatic sediments at short time scales: model selection ………………… 239-254 Gingras MK, Dashtgard SE, MacEachern JA, Pemberton SG Biology of shallow marine ichnology: a modern perspective ……………………………………….……… 255-268 White DS, Miller MF Benthic invertebrate activity in lakes: linking present and historical bioturbation patterns ……… 269-277 Herringshaw LG, Davies NS Bioturbation levels during the end-Ordovician extinction event: a case study of shallow marine strata from the Welsh Basin ………………… 279-287 Solan M, Batty P, Bulling MT, Godbold JA How biodiversity affects ecosystem processes: implications for ecological revolutions and benthic ecosystem function …………………….……… 289-301 Resale or republication not permitted without written consent of the publisher

Zoological Journal of The Linnean Society, 2007

Lepidaster grayi Forbes, 1850, from the Much Wenlock Limestone Formation (Silurian: Wenlock) of E... more Lepidaster grayi Forbes, 1850, from the Much Wenlock Limestone Formation (Silurian: Wenlock) of England, is the earliest species of starfish (Echinodermata: Asteroidea) to deviate from pentaradial symmetry, having 13 rays rather than five. Based on the patterns of supernumerary ray development seen in extant multiradiate asteroids, two possible models are evaluated for the origin of the eight additional rays seen in L. grayi. In the ‘all-in-one’ model, all rays were added in the same interradius, whereas in the ‘quadrants’ model generations of rays would have been added in each of four interradii. The smallest specimen of L. grayi, apparently having only nine rays, suggests that the ‘quadrants’ model is most probable for the species. The presence of supernumerary rays in Silurian starfish, coupled with the existence of numerous other Palaeozoic multiradiate taxa, shows that asteroids have been able to deviate from pentamerism for most of their evolutionary history, and the variety of methods of supernumerary ray addition indicates that the multiradiate condition is homoplastic. The ecological significance of multiradiate Palaeozoic starfish is reviewed: the mouth frame of L. grayi had considerably greater flexibility than that of contemporaneous five-rayed species and, in combination with its supernumerary rays, enabled L. grayi to manipulate and consume larger food items. It is probable that Silurian starfish utilized a similar range of trophic guilds as those exploited by extant taxa. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 150, 743–754.

Zoological Journal of The Linnean Society, 2007

The genus Cornulites, with the type species C. serpularius Schlotheim, 1820, from the Silurian of... more The genus Cornulites, with the type species C. serpularius Schlotheim, 1820, from the Silurian of Gotland, comprises annulated, conical or tubular calcite shells, often found attached to the hard parts of other organisms. No consensus has ever been reached over the zoological affinities of the taxon, and no examples of soft-part preservation are known: detailed examination of shell structures and growth patterns provide the only means of assessing its systematic position. Using transverse and longitudinal thin sections of C. serpularius Vine, 1882, and C. cellulosus sp. nov., from the Much Wenlock Limestone Formation of England, the shell structure of Cornulites is shown to be lamellar, but with conspicuous internal chambers (camerae) at the apical end of the shell and, particularly in C. cellulosus, numerous smaller vacuities (cellulae) between the lamellae in the apertural shell region. Growth of the shell was by the secretion of low-magnesian calcite increments within one another, giving a cone-in-cone structure, with the prominent development of cellulae in C. cellulosus probably a constructional feature relating to an upright life position. By comparison of morphology and shell structure with other taxa, the zoological affinities of Cornulites are re-examined; previously suggested affinities with annelids, foraminifers, molluscs and poriferans can be ruled out. Specific shell structures, most notably pseudopuncta similar to those of bryozoans and brachiopods, have led some recent workers to interpret cornulitids as lophophorates. However, it is shown that they can be interpreted alternatively as solitary, aseptate members of the stem-Zoantharia (Cnidaria: Anthozoa). Four cornulitid species are recognized in the Much Wenlock Limestone Formation: C. cellulosus sp. nov., C. gremialis sp. nov., C. scalariformis and C. serpularius. In the absence of the type material, C. serpularius is here restricted to cornulitids closely resembling the specimens originally figured by Schlotheim. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 150, 681–699.

Palaeontology, 2007

Abstract: Although their record extends back to the Early Ordovician, the occurrence of fossil s... more Abstract: Although their record extends back to the Early Ordovician, the occurrence of fossil starfish (Echinodermata: Asteroidea) is dependent almost exclusively upon horizons of exceptional preservation. Thus, asteroids found in Silurian obrution deposits of the English Midlands and Welsh Borderlands are particularly significant to an understanding of the early diversity of the group. Six species are described here: Hudsonaster? carectum sp. nov. (Hudsonasteridae), from the lower part of the Lower Elton Formation; and, from the Much Wenlock Limestone Formation, the hudsonasterids Doliaster brachyactis gen. et sp. nov. and Siluraster? ketleyi (Spencer, 1916), the lepidasterids Lepidaster grayi Forbes, 1850 and Lepidactis wenlocki Spencer, 1918, and the palasterinid Palasterina orchilocalia sp. nov. Though few in number, they show a diverse range of body morphologies when compared with Ordovician taxa: L. wenlocki had long, slender rays when fully grown whereas D. brachyactis is the first asteroid with the short-rayed body form of extant cushion stars. Most distinctive of all is L. grayi, the earliest multiradiate taxon known, all complete specimens of which have 13 rays. This morphological variety is interpreted as indicating that by the Early Silurian starfish were exploiting a wide range of feeding habits and ecological niches.

Lethaia, 2009

The Lower Cambrian Eriboll Formation of northwest Scotland is renowned for the high density, low ... more The Lower Cambrian Eriboll Formation of northwest Scotland is renowned for the high density, low diversity trace fossils (Skolithos ichnofacies) found in its upper Pipe Rock Member. Ichnofabric analysis of the member indicates that relatively small examples of Skolithos terminating at the same foreset boundary were formed during a brief colonization window after a single depositional event, that particularly long Skolithos specimens are equilibrichnia, and that palimpsests of Skolithos represent the marginal, slightly deeper water fringes of the Pipe Rock Member depositional environment. Nearest neighbour analysis, however, suggests that such palimpsests were uncommon. A much more diverse trace fossil assemblage is present in the overlying Fucoid Member (An t-Sròn Formation), comprising Cruziana barbata, Dactylophycus, Didymaulichnus, Halopoa imbricata, ?Margaritichnus, Monocraterion, Monomorphichnus, Palaeophycus striatus, P. tubularis, ?Phycodes, Planolites montanus, ?Polarichnus, Rusophycus ramellensis, ?Psammichnites, Skolithos and various unidentified traces, and represents the Cruziana ichnofacies. Above the Fucoid Member, the Salterella Grit Member ichnofauna is more impoverished, yielding only Cruziana, Monocraterion, Rusophycus, Skolithos and ?Spirophyton. The ichnological variations between the Pipe Rock, Fucoid and Salterella Grit members are interpreted as being driven by changes in sea level. The low trace fossil diversity in the Pipe Rock Member indicates opportunistic colonization of laterally extensive, shoreface sediments deposited by regular influxes of terrigenous material, which were overlain by more distal, ichnologically diverse sediments (Fucoid Member) as sea level rose. A minor regression then caused an increase in terrigenous sediment input, producing an impoverished, proximal Cruziana ichnofacies (Salterella Grit Member).

Ichnos, 2012

Creek Canyon in the Book Cliffs of Utah, USA-the type locality of the ichnospecies-allows us to a... more Creek Canyon in the Book Cliffs of Utah, USA-the type locality of the ichnospecies-allows us to assess the validity of pellet morphology as an ichnotaxobase for species-level identification. The importance of O. irregulaire stems from its abundance in petroliferous shallow marine strata of post-Paleozoic age. Our three-dimensional reconstruction of the burrow wall of O. irregulaire demonstrates for the first time that it is composed of sand-cored pellets. The typically spiky nature of the pellets in cross-section is inferred to result from differential compaction of the sand core and pelletal lining. Rupturing of the thin outer clay coating of the sand pellets is considered to produce the distinctively attenuated, spiky outer surface to the burrow wall of this ichnospecies. This study demonstrates the utility of pellet morphology in species-level classification of Ophiomorpha and lends support to O. irregulaire being a cosmopolitan ichnospecies present in post-Paleozoic strata. It also demonstrates the need to ensure that ichnotaxonomic identifications are based on threedimensional knowledge of the trace fossil in question.

Scottish Journal of Geology, 2007

A machaeridian sclerite from a thrombolite bed in the Sangomore Formation (Durness Group: Tremado... more A machaeridian sclerite from a thrombolite bed in the Sangomore Formation (Durness Group: Tremadoc) is the first to be described from NW Scotland. The large size, thickness and coarsely spaced rugae indicate the sclerite is that of a turrilepadid, but its morphology is distinct from any taxon described previously. Lacking a longitudinal fold and with three major inflections present along the accreting margin, it is interpreted as an outer right sclerite. It is the oldest turrilepadid yet recorded and shows that all three major groups of the problematical Machaeridia were present in the early Ordovician.

Palaeogeography Palaeoclimatology Palaeoecology, 2009

Reliable identification of trace fossils in core is a significant challenge to applied ichnologis... more Reliable identification of trace fossils in core is a significant challenge to applied ichnologists. Sedimentological models are commonly refined by the addition of ichnological datasets derived from core material. Unfortunately very few original descriptions and diagnoses of ichnological taxa include a full range of descriptions and cross sections to aid in core-based recognition. Ophiomorpha irregulaire is a case-in-point in that it is incompletely known in 3D from field specimens, and has become increasingly commonly recognised in core material based on pellet morphology. Recent work (Bromley & Pedersen 2008) has highlighted the fact that the meander maze of O. irregulaire cannot be seen in core due to a difference in scale of observation. This work highlights the need for a reassessment of pellet morphology in the type material, and makes direct comparisons of pellet morphology in O. irregulaire from the type area with material from other regions. We thereby consider that, contrary to earlier assertions, O. irregulaire is widely distributed in the Mesozoic, and reject palaeogeographic and stratigraphic criteria for restricting the use of the name to material from the Western Interior Seaway.

Zoological Journal of the Linnean Society

The genus Cornulites , with the type species C. serpularius Schlotheim, 1820, from the Silurian o... more The genus Cornulites , with the type species C. serpularius Schlotheim, 1820, from the Silurian of Gotland, comprises annulated, conical or tubular calcite shells, often found attached to the hard parts of other organisms. No consensus has ever been reached over the zoological affinities of the taxon, and no examples of soft-part preservation are known: detailed examination of shell structures and growth patterns provide the only means of assessing its systematic position. Using transverse and longitudinal thin sections of C. serpularius Vine, 1882, and C. cellulosus sp. nov. , from the Much Wenlock Limestone Formation of England, the shell structure of Cornulites is shown to be lamellar, but with conspicuous internal chambers (camerae) at the apical end of the shell and, particularly in C. cellulosus , numerous smaller vacuities (cellulae) between the lamellae in the apertural shell region. Growth of the shell was by the secretion of low-magnesian calcite increments within one another, giving a cone-in-cone structure, with the prominent development of cellulae in C. cellulosus probably a constructional feature relating to an upright life position. By comparison of morphology and shell structure with other taxa, the zoological affinities of Cornulites are re-examined; previously suggested affinities with annelids, foraminifers, molluscs and poriferans can be ruled out. Specific shell structures, most notably pseudopuncta similar to those of bryozoans and brachiopods, have led some recent workers to interpret cornulitids as lophophorates. However, it is shown that they can be interpreted alternatively as solitary, aseptate members of the stem-Zoantharia (Cnidaria: Anthozoa). Four cornulitid species are recognized in the Much Wenlock Limestone Formation: C. cellulosus sp. nov. , C. gremialis sp. nov. , C. scalariformis and C. serpularius . In the absence of the type material, C. serpularius is here restricted to cornulitids closely resembling the specimens originally figured by Schlotheim.

ABSTRACT Regularly-spaced arrays of opening-mode fractures develop in brittle layers (sandstone, ... more ABSTRACT Regularly-spaced arrays of opening-mode fractures develop in brittle layers (sandstone, limestone) that are embedded within a weaker matrix (shale) and subjected to layer-parallel extension. Where cut by tectonic faults, such brittle layers display a range of features including drag folds, shear fractures and rotated blocks, in addition to opening-mode fractures. In both cases, the weaker matrix deforms in a macroscopically ductile manner. Knowledge of the "mechanical stratigraphy" can therefore aid fracture prediction in subsurface reservoirs. A key question for unconventional hydrocarbon exploration is to what extent does the concept of mechanical stratigraphy apply to thick, shale-dominated sequences? The Toarcian (Lower Jurassic) Whitby Mudstone Formation (WMF) is a ca. 105 m thick, shale-dominated sequence that crops out within the Cleveland Basin, NE England and was deposited in < 7.4 Myr. The WMF contains both black and grey shale intervals. The lowermost Mulgrave Shale Member ("Jet Rock"; Harpoceras falciferum Zone, Cleviceras exaratum Subzone) of the WMF is characterised by high total organic carbon (TOC < 18 %), but low SiO2, Al2O3 and K2O. TOC decreases, but SiO2, Al2O3 and K2O all increase above the exaratum Subzone ("Bituminous Shales"). These geochemical variations are consistent with an upward increase in quartz and clay content within the Mulgrave Shale Member. The upper part of the Alum Shale Member ("Cement Shales"; Hildoceras bifrons Zone, Zugodactylites braunianus Subzone) is characterised by low TOC, Al2O3 and K2O, but high SiO2 consistent with a high quartz and low clay content. The Jet Rock and Bituminous Shales are cut by regularly-spaced arrays of sub-vertical, calcite-filled opening-mode fractures that abut against sub-horizontal, bedding-parallel fractures with ca. 1 m vertical spacing. By contrast, the Cement Shales are characterised by arrays of dipping (dip < 60° ) shear fractures with consistent extensional offsets. We hypothesise that large fluid overpressures (? ? 1) generated during clay diagenesis and/or kerogen maturation within the highly stratified (i.e. mechanically isotropic) Mulgrave Shale Member contributed to the development of bedding-parallel veins within the Jet Rock and Bituminous Shale. More speculatively, the spacing of the bedding-parallel veins may be controlled by metre- and sub-metre scale variations in organic and/or clay content throughout the Mulgrave Shale Member, which in turn may reflect primary sedimentary discontinuities. The regular spacing of compositional variations and discontinuity surfaces is likely to be a consequence of allogenic forcing mechanisms. By contrast, the SiO2-rich, TOC- and clay-poor Cement Shales appear to be compositionally more homogeneous. The Cement Shales deformed under conditions of higher effective normal stress (? < 1), giving rise to shear fractures with classic Andersonian geometries. Our observations suggest that stratigraphy exerts a strong control on fracturing within thick, shale-dominated sequences. However, the relationship between "mechanical stratigraphy" and fracture spacing and orientation appears to be more complex than in conventional clastic reservoir sequences.

Palaeogeography, Palaeoclimatology, Palaeoecology, 2015

AAPG Bulletin, 2014

ABSTRACT Faults and fractures within the well-exposed Lower Jurassic Cleveland Ironstone and Whit... more ABSTRACT Faults and fractures within the well-exposed Lower Jurassic Cleveland Ironstone and Whitby Mudstone Formations may provide insights into the tectonic history of gas-prospective, Mississippian shale in northern England. Subvertical opening mode fractures occur throughout the Cleveland Basin. Bed-parallel fractures, some of which contain blocky calcite fills, occur preferentially within well-bedded, clay-rich mudstones of the Cleveland Ironstone and Whitby Mudstone Formations at Jet Wyke and Port Mulgrave. Subvertical fractures display abutting or curving-parallel relationships with under- and overlying bed-parallel fractures. Together, these observations suggest that bed-parallel fractures, at times, acted as free surfaces. Some bed-parallel fractures curve toward and branch from calcite-filled fault slip surfaces, indicating that bed-parallel fracturing and normal faulting were synchronous, occurring within a regional stress field with vertical maximum principal stress. This apparent paradox can be explained by normal compaction, followed by cementation and coupling between pore pressure and minimum horizontal stress driven by poroelastic deformation or incipient slip along critically stressed normal faults, causing elevation of horizontal stress in excess of the vertical stress within clay-rich units. Propagation of bed-parallel fractures was enhanced by dilatational strains adjacent to normal fault planes. Bed-parallel fractures have not been observed within more Formula -rich units at the top of the Whitby Mudstone Formation at Whitby East Cliff, or within well-bedded, clay-rich shale at Saltwick Nab. This observation is consistent with the lack of normal faulting at Saltwick Nab, and the Whitby Mudstone Formation having been drained by structural and/or stratigraphical juxtaposition against permeable Middle Jurassic sandstones at both these localities.

This fieldtrip will introduce you to the late Ediacaran paleobiology and ichnology of Newfoundlan... more This fieldtrip will introduce you to the late Ediacaran paleobiology and ichnology of Newfoundland, and will touch upon some of the most interesting current debates and research areas in this field. Newfoundland contains some of the world’s best exposures of latest Neoproterozoic sedimentary successions. Although Cryogenian and early Ediacaran sedimentary units are not exposed in Newfoundland, deposits relating to the Gaskiers glaciation (considered by some to represent the final ‘Snowball Earth’ event), and extensive late Ediacaran fossil-bearing units, are well displayed and have been the subject of extensive study sciences in Canada and the world.

Data from around the world (and the USA) show that more than four million onshore hydrocarbon wel... more Data from around the world (and the USA) show that more than four million onshore hydrocarbon wells have been drilled globally.

Journal of Sedimentary Research, Jun 2013

Palaios, 2010

Modification of event beds by the burrowing nereidid polychaete Alitta virens (Sars) was examined... more Modification of event beds by the burrowing nereidid polychaete Alitta virens (Sars) was examined using laboratory microcosms, to assess its importance as an ecosystem engineer in pristine sediments. In all microcosms, the nereidids modified their environment to permit longterm occupation, but different behavioral strategies and burrow morphologies were observed based on sediment characteristics and nutrient availability. Alitta virens utilized scavenging, surface deposit feeding, suspension feeding, microbial gardening, deposit feeding at depth, and cannibalism. Suspension feeding using mucus nets is used by many nereidids but has not been documented previously in A. virens; extended use of the technique may indicate low availability of biotic sediments for deposit feeding. Alitta virens typically produced burrows similar to Arenicolites and Skolithos, but morphologies resembling Polykladichnus, Planolites, Palaeophycus, and Thalassinoides were formed under differing sedimentary conditions and over different time scales. In the rock record, such ichnological diversity might be interpreted as indicating paleoecological diversity, rather than the response of one taxon to changing conditions. Alitta virens is an allogenic ecosystem engineer, its behavior changing the physical and geochemical characters of its environment. These changes, combined with the widespread occurrence and population longevity of A. virens, demonstrate that burrowing polychaetes are important ecosystem engineers in shallow marine environments, and are likely to have been so over geological time scales.

Aquatic Biology, Jun 2008

The Ordovician-Silurian succession of the Llandovery area, mid-Wales, preserves shallow marine se... more The Ordovician-Silurian succession of the Llandovery area, mid-Wales, preserves shallow marine sediments deposited during the Hirnantian (end-Ordovician) extinction event. Ichnological analysis of the rocks shows that the degree and depth of bioturbation in this part of the Welsh Basin was often low across this interval, both during glacioeustatic sea level fall and the early part of the subsequent transgression. This pattern suggests that stratigraphic dilution was not the primary control on trace fossil abundance: an increase in sediment supply during the regression could explain low abundance in early Hirnantian units, but not in the post-glacial transgressive strata. A significant decrease in oxygen levels during sea level rise might be invoked instead, but this cannot have been the sole cause, as the occurrence of burrows up to 20 mm in diameter in the Bronydd Formation (late Hirnantian-Rhuddanian) shows that seafloor oxygen levels were at least intermittently high. An absence of vertical bioturbation through much of the succession indicates that sessile, suspensionfeeding organisms were generally scarce. The overall pattern probably reflects a decline in benthic infauna during the extinction event, but the 2 pulses of extinction described previously in body fossils are not evident ichnologically in this part of the Welsh Basin.

Aquatic Biology, 2010

Herringshaw LG, Solan M Benthic bioturbation in the past, present and future ………………………………………………… ... more Herringshaw LG, Solan M Benthic bioturbation in the past, present and future ………………………………………………… 201-205 Teal LR, Bulling MT, Parker ER, Solan M Global patterns of bioturbation intensity and mixed depth of marine soft sediments ……………… 207-218 Maire O, Lecroart P, Meysman F, Rosenberg R, Duchêne JC, Grémare A Quantification of sediment reworking rates in bioturbation research: a review ……………………… 219-238 Meysman FJR, Malyuga VS, Boudreau BP, Middelburg JJ Quantifying particle dispersal in aquatic sediments at short time scales: model selection ………………… 239-254 Gingras MK, Dashtgard SE, MacEachern JA, Pemberton SG Biology of shallow marine ichnology: a modern perspective ……………………………………….……… 255-268 White DS, Miller MF Benthic invertebrate activity in lakes: linking present and historical bioturbation patterns ……… 269-277 Herringshaw LG, Davies NS Bioturbation levels during the end-Ordovician extinction event: a case study of shallow marine strata from the Welsh Basin ………………… 279-287 Solan M, Batty P, Bulling MT, Godbold JA How biodiversity affects ecosystem processes: implications for ecological revolutions and benthic ecosystem function …………………….……… 289-301 Resale or republication not permitted without written consent of the publisher

Zoological Journal of The Linnean Society, 2007

Lepidaster grayi Forbes, 1850, from the Much Wenlock Limestone Formation (Silurian: Wenlock) of E... more Lepidaster grayi Forbes, 1850, from the Much Wenlock Limestone Formation (Silurian: Wenlock) of England, is the earliest species of starfish (Echinodermata: Asteroidea) to deviate from pentaradial symmetry, having 13 rays rather than five. Based on the patterns of supernumerary ray development seen in extant multiradiate asteroids, two possible models are evaluated for the origin of the eight additional rays seen in L. grayi. In the ‘all-in-one’ model, all rays were added in the same interradius, whereas in the ‘quadrants’ model generations of rays would have been added in each of four interradii. The smallest specimen of L. grayi, apparently having only nine rays, suggests that the ‘quadrants’ model is most probable for the species. The presence of supernumerary rays in Silurian starfish, coupled with the existence of numerous other Palaeozoic multiradiate taxa, shows that asteroids have been able to deviate from pentamerism for most of their evolutionary history, and the variety of methods of supernumerary ray addition indicates that the multiradiate condition is homoplastic. The ecological significance of multiradiate Palaeozoic starfish is reviewed: the mouth frame of L. grayi had considerably greater flexibility than that of contemporaneous five-rayed species and, in combination with its supernumerary rays, enabled L. grayi to manipulate and consume larger food items. It is probable that Silurian starfish utilized a similar range of trophic guilds as those exploited by extant taxa. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 150, 743–754.

Zoological Journal of The Linnean Society, 2007

The genus Cornulites, with the type species C. serpularius Schlotheim, 1820, from the Silurian of... more The genus Cornulites, with the type species C. serpularius Schlotheim, 1820, from the Silurian of Gotland, comprises annulated, conical or tubular calcite shells, often found attached to the hard parts of other organisms. No consensus has ever been reached over the zoological affinities of the taxon, and no examples of soft-part preservation are known: detailed examination of shell structures and growth patterns provide the only means of assessing its systematic position. Using transverse and longitudinal thin sections of C. serpularius Vine, 1882, and C. cellulosus sp. nov., from the Much Wenlock Limestone Formation of England, the shell structure of Cornulites is shown to be lamellar, but with conspicuous internal chambers (camerae) at the apical end of the shell and, particularly in C. cellulosus, numerous smaller vacuities (cellulae) between the lamellae in the apertural shell region. Growth of the shell was by the secretion of low-magnesian calcite increments within one another, giving a cone-in-cone structure, with the prominent development of cellulae in C. cellulosus probably a constructional feature relating to an upright life position. By comparison of morphology and shell structure with other taxa, the zoological affinities of Cornulites are re-examined; previously suggested affinities with annelids, foraminifers, molluscs and poriferans can be ruled out. Specific shell structures, most notably pseudopuncta similar to those of bryozoans and brachiopods, have led some recent workers to interpret cornulitids as lophophorates. However, it is shown that they can be interpreted alternatively as solitary, aseptate members of the stem-Zoantharia (Cnidaria: Anthozoa). Four cornulitid species are recognized in the Much Wenlock Limestone Formation: C. cellulosus sp. nov., C. gremialis sp. nov., C. scalariformis and C. serpularius. In the absence of the type material, C. serpularius is here restricted to cornulitids closely resembling the specimens originally figured by Schlotheim. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 150, 681–699.

Palaeontology, 2007

Abstract: Although their record extends back to the Early Ordovician, the occurrence of fossil s... more Abstract: Although their record extends back to the Early Ordovician, the occurrence of fossil starfish (Echinodermata: Asteroidea) is dependent almost exclusively upon horizons of exceptional preservation. Thus, asteroids found in Silurian obrution deposits of the English Midlands and Welsh Borderlands are particularly significant to an understanding of the early diversity of the group. Six species are described here: Hudsonaster? carectum sp. nov. (Hudsonasteridae), from the lower part of the Lower Elton Formation; and, from the Much Wenlock Limestone Formation, the hudsonasterids Doliaster brachyactis gen. et sp. nov. and Siluraster? ketleyi (Spencer, 1916), the lepidasterids Lepidaster grayi Forbes, 1850 and Lepidactis wenlocki Spencer, 1918, and the palasterinid Palasterina orchilocalia sp. nov. Though few in number, they show a diverse range of body morphologies when compared with Ordovician taxa: L. wenlocki had long, slender rays when fully grown whereas D. brachyactis is the first asteroid with the short-rayed body form of extant cushion stars. Most distinctive of all is L. grayi, the earliest multiradiate taxon known, all complete specimens of which have 13 rays. This morphological variety is interpreted as indicating that by the Early Silurian starfish were exploiting a wide range of feeding habits and ecological niches.

Lethaia, 2009

The Lower Cambrian Eriboll Formation of northwest Scotland is renowned for the high density, low ... more The Lower Cambrian Eriboll Formation of northwest Scotland is renowned for the high density, low diversity trace fossils (Skolithos ichnofacies) found in its upper Pipe Rock Member. Ichnofabric analysis of the member indicates that relatively small examples of Skolithos terminating at the same foreset boundary were formed during a brief colonization window after a single depositional event, that particularly long Skolithos specimens are equilibrichnia, and that palimpsests of Skolithos represent the marginal, slightly deeper water fringes of the Pipe Rock Member depositional environment. Nearest neighbour analysis, however, suggests that such palimpsests were uncommon. A much more diverse trace fossil assemblage is present in the overlying Fucoid Member (An t-Sròn Formation), comprising Cruziana barbata, Dactylophycus, Didymaulichnus, Halopoa imbricata, ?Margaritichnus, Monocraterion, Monomorphichnus, Palaeophycus striatus, P. tubularis, ?Phycodes, Planolites montanus, ?Polarichnus, Rusophycus ramellensis, ?Psammichnites, Skolithos and various unidentified traces, and represents the Cruziana ichnofacies. Above the Fucoid Member, the Salterella Grit Member ichnofauna is more impoverished, yielding only Cruziana, Monocraterion, Rusophycus, Skolithos and ?Spirophyton. The ichnological variations between the Pipe Rock, Fucoid and Salterella Grit members are interpreted as being driven by changes in sea level. The low trace fossil diversity in the Pipe Rock Member indicates opportunistic colonization of laterally extensive, shoreface sediments deposited by regular influxes of terrigenous material, which were overlain by more distal, ichnologically diverse sediments (Fucoid Member) as sea level rose. A minor regression then caused an increase in terrigenous sediment input, producing an impoverished, proximal Cruziana ichnofacies (Salterella Grit Member).

Ichnos, 2012

Creek Canyon in the Book Cliffs of Utah, USA-the type locality of the ichnospecies-allows us to a... more Creek Canyon in the Book Cliffs of Utah, USA-the type locality of the ichnospecies-allows us to assess the validity of pellet morphology as an ichnotaxobase for species-level identification. The importance of O. irregulaire stems from its abundance in petroliferous shallow marine strata of post-Paleozoic age. Our three-dimensional reconstruction of the burrow wall of O. irregulaire demonstrates for the first time that it is composed of sand-cored pellets. The typically spiky nature of the pellets in cross-section is inferred to result from differential compaction of the sand core and pelletal lining. Rupturing of the thin outer clay coating of the sand pellets is considered to produce the distinctively attenuated, spiky outer surface to the burrow wall of this ichnospecies. This study demonstrates the utility of pellet morphology in species-level classification of Ophiomorpha and lends support to O. irregulaire being a cosmopolitan ichnospecies present in post-Paleozoic strata. It also demonstrates the need to ensure that ichnotaxonomic identifications are based on threedimensional knowledge of the trace fossil in question.

Scottish Journal of Geology, 2007

A machaeridian sclerite from a thrombolite bed in the Sangomore Formation (Durness Group: Tremado... more A machaeridian sclerite from a thrombolite bed in the Sangomore Formation (Durness Group: Tremadoc) is the first to be described from NW Scotland. The large size, thickness and coarsely spaced rugae indicate the sclerite is that of a turrilepadid, but its morphology is distinct from any taxon described previously. Lacking a longitudinal fold and with three major inflections present along the accreting margin, it is interpreted as an outer right sclerite. It is the oldest turrilepadid yet recorded and shows that all three major groups of the problematical Machaeridia were present in the early Ordovician.

Palaeogeography Palaeoclimatology Palaeoecology, 2009

Reliable identification of trace fossils in core is a significant challenge to applied ichnologis... more Reliable identification of trace fossils in core is a significant challenge to applied ichnologists. Sedimentological models are commonly refined by the addition of ichnological datasets derived from core material. Unfortunately very few original descriptions and diagnoses of ichnological taxa include a full range of descriptions and cross sections to aid in core-based recognition. Ophiomorpha irregulaire is a case-in-point in that it is incompletely known in 3D from field specimens, and has become increasingly commonly recognised in core material based on pellet morphology. Recent work (Bromley & Pedersen 2008) has highlighted the fact that the meander maze of O. irregulaire cannot be seen in core due to a difference in scale of observation. This work highlights the need for a reassessment of pellet morphology in the type material, and makes direct comparisons of pellet morphology in O. irregulaire from the type area with material from other regions. We thereby consider that, contrary to earlier assertions, O. irregulaire is widely distributed in the Mesozoic, and reject palaeogeographic and stratigraphic criteria for restricting the use of the name to material from the Western Interior Seaway.

In this presentation, we describe a new form of intra-sedimentary particle transport, caused by t... more In this presentation, we describe a new form of intra-sedimentary particle transport, caused by the bioirrigating activities of burrowing organisms. In laboratory mesocosms, particles of kaolinite clay were found to be transported advectively into pore spaces close to the interface between two buried sand layers by the burrow-ventilating activities of the mud shrimp Upogebia pugettensis. The term ‘bioinfiltration’ is used to describe the process. Given the abundance of bioirrigating organisms in shallow marine environments, bioinfiltration may be a widespread phenomenon affecting the properties of large sediment volumes. Clay minerals commonly act as sites of early diagenesis of clay mineral cements, thereby controlling the porosity and permeability of sedimentary rocks. Bioinfiltration needs to be considered, therefore, when assessing the diagenesis of bioturbated sediments. More broadly, the potential for bioinfiltration of other clay-grade materials will be of significance to sediment biogeochemistry and ecology, particularly if these materials are rich in organic matter or other bioavailable particulate nutrients.