Lingulid brachiopods and Lingulichnus from a Silurian shelf–slope carbonate sequence, Delorme Group, Mackenzie Mountains, Northwest Territories

1988 ◽  
Vol 25 (3) ◽  
pp. 465-471 ◽  
Author(s):  
D. Jeffrey Over
Keyword(s):  
Northwest Territories ◽  
Substrate Surface ◽  
Benthic Fauna ◽  
Low Energy ◽  
High Abundance ◽  
Energy Conditions ◽  
Bottom Current ◽  
Shelf Slope ◽  
Low Diversity ◽  
Carbonate Sequence

Structures assigned to the ichnogenus Lingulichnus, commonly containing the burrow-forming brachiopod, were collected from an argillaceous unit in a Silurian shelf dolostone sequence (Delorme Group). The sediments, benthic fauna, and inclined orientation of all lingulid burrows indicate the presence of a bottom current and restricted conditions on the margin of the Selwyn Basin. High-abundance–low-diversity faunas of lingulids and Lingulichnus are indicative of limiting conditions at the substrate surface. Under low-energy conditions, they seem to be indicative of the Zoophycos ichnofacies.

Sedimentary fades, depositional environments, and faunal associations of the lower Llandovery (Silurian) Beechill Cove Formation, Arisaig, Nova Scotia

1983 ◽  
Vol 20 (12) ◽  
pp. 1761-1779 ◽  
Author(s):  
R. K. Pickerill ◽  
J. M. Hurst
Keyword(s):  
Depositional Environments ◽  
Low Energy ◽  
Sedimentation Rates ◽  
Storm Activity ◽  
Distributional Patterns ◽  
Low Diversity ◽  
Energy Environment ◽  
Shallow Subtidal ◽  
Oxygen Minimum ◽  
Mudstone Facies

Six facies are recognised in the Beechill Cove Formation. These are: (1) conglomerate facies deposited as a transgressive beach lag; (2) red shale facies deposited in shoreface environments; (3) mottled mudstone facies; extensively bioturbated sediments indicative of shallow subtidal areas influenced by low sedimentation rates; (4) regular layered facies; shelf turbidites generated by storm activity and superimposed on quiescent subtidal environments; (5) lenticular facies, including a thinner bedded more persistent and a thicker bedded lenticular subfacies, induced by storm activity and deposited in shallow subtidal environments; and (6) laminated shale facies produced by sediment fallout from suspension in a low-energy environment where the oxygen, minimum layer intersected the sediment–water interface. Three faunal associations occur, which have distinct distributional patterns. The Lingula clintoni association, which is characterized by L. clintoni in life position and a moderately diverse but abundant trace-fossil assemblage, is restricted to the mottled mudstone facies. The Leptostrophia beechillensis association, a transported residue, is dominated by brachiopods and restricted to the regular layered facies. The low-diversity Dalmanella primitiva association is transported and restricted to the lenticular facies. No faunas are known from the conglomerate or laminated shale facies, and only rare trace fossils occur in the red shale facies.

scholarly journals Linking evolutionary mode to palaeoclimate change reveals rapid radiations of staphylinoid beetles in low-energy conditions

2019 ◽  
Vol 66 (4) ◽  
pp. 435-444 ◽  
Author(s):  
Liang Lü ◽  
Chen-Yang Cai ◽  
Xi Zhang ◽  
Alfred F Newton ◽  
Margaret K Thayer ◽  
...  
Keyword(s):  
Body Size ◽  
Rapid Evolution ◽  
High Energy ◽  
Low Energy ◽  
Diversification Rate ◽  
Energy Conditions ◽  
Climate Factors ◽  
Direct Outcome ◽  
Rapid Radiations ◽  
Evolutionary Mode

Abstract Staphylinoidea (Insecta: Coleoptera) is one of the most species-rich groups in animals, but its huge diversity can hardly be explained by the popular hypothesis (co-radiation with angiosperms) that applies to phytophagous beetles. We estimated the evolutionary mode of staphylinoid beetles and investigated the relationship between the evolutionary mode and palaeoclimate change, and thus the factors underlying the current biodiversity pattern of staphylinoid beetles. Our results demonstrate that staphylinoid beetles originated at around the Triassic–Jurassic bound and the current higher level clades underwent rapid evolution (indicated by increased diversification rate and decreased body size disparity) in the Jurassic and in the Cenozoic, both with low-energy climate, and they evolved much slower during the Cretaceous with high-energy climate. Climate factors, especially low O2 and high CO2, promoted the diversification rate and among-clade body size disparification in the Jurassic. In the Cenozoic, however, climate factors had negative associations with diversification rate but little with body size disparification. Our present study does not support the explosion of staphylinoid beetles as a direct outcome of the Cretaceous Terrestrial Revolution (KTR). We suppose that occupying and diversifying in refuge niches associated with litter may elucidate rapid radiations of staphylinoid beetles in low-energy conditions.

A NEW TEICHICHNOID TRACE FOSSIL SYRINGOMORPHA CYPRENSIS FROM THE MIOCENE OF CYPRUS

Palaios ◽  
2019 ◽  
Vol 34 (10) ◽  
pp. 506-514 ◽  
Author(s):  
OLMO MIGUEZ-SALAS ◽  
FRANCISCO J. RODRÍGUEZ-TOVAR ◽  
ALFRED UCHMAN
Keyword(s):  
Deep Sea ◽  
Trace Fossil ◽  
Taxonomic Group ◽  
Energy Conditions ◽  
Bottom Current ◽  
Lower Paleozoic ◽  
Shallow Marine ◽  
Current Flows

ABSTRACTA new teichichnoid trace fossil, Syringomorpha cyprensis from the Miocene of Cyprus, is proposed as a vertical burrow composed of an arcuate-like tube with horizontal parts to subhorizontal distally and vertical to subvertical parts proximally and triangular spreiten in the inner corner of the tube. Previously, this ichnogenus was represented only by the lower Paleozoic, shallow marine S. nilssoni, which disappeared after the Cambrian. Syringomorpha cyprensis marks the reappearance of similar behavior, in a deep-sea environment with pelagic, contouritic, and turbiditic sedimentation, influenced by frequent turbiditic and bottom current flows. Both ichnospecies of Syringomorpha could be produced by the same taxonomic group of probable worm like organisms (polychaetes?). Energy conditions were a stronger influence on the distribution of S. cyprensis tracemaker rather depth.

scholarly journals Deformation of an elastic substrate due to a resting sessile droplet

2017 ◽  
Vol 29 (2) ◽  
pp. 281-300 ◽  
Author(s):  
AARON BARDALL ◽  
KAREN E. DANIELS ◽  
MICHAEL SHEARER
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Substrate Surface ◽  
Fluid Pressure ◽  
Force Balance ◽  
Energy Conditions ◽  
Equilibrium Contact Angle ◽  
Solution Technique ◽  
Vertical Force ◽  
Tangential Contact

On a sufficiently soft substrate, a resting fluid droplet will cause significant deformation of the substrate. This deformation is driven by a combination of capillary forces at the contact line and the fluid pressure at the solid surface. These forces are balanced at the surface by the solid traction stress induced by the substrate deformation. Young's Law, which predicts the equilibrium contact angle of the droplet, also indicates an a priori radial force balance for rigid substrates, but not necessarily for soft substrates that deform under loading. It remains an open question whether the contact line transmits a non-zero force tangent to the substrate surface in addition to the conventional normal (vertical) force. We present an analytic Fourier transform solution technique that includes general interfacial energy conditions, which govern the contact angle of a 2D droplet. This includes evaluating the effect of gravity on the droplet shape in order to determine the correct fluid pressure at the substrate surface for larger droplets. Importantly, we find that in order to avoid a strain singularity at the contact line under a non-zero tangential contact line force, it is necessary to include a previously neglected horizontal traction boundary condition. To quantify the effects of the contact line and identify key quantities that will be experimentally accessible for testing the model, we evaluate solutions for the substrate surface displacement field as a function of Poisson's ratio and zero/non-zero tangential contact line forces.

Sign in / Sign up

Export Citation Format

Share Document