Global correlation of the radiolarian faunal change across the Triassic–Jurassic boundary

2005 ◽  
Vol 42 (5) ◽  
pp. 777-790 ◽  
Author(s):  
Elizabeth S Carter ◽  
Rie S Hori
Keyword(s):  
Global Changes ◽  
Sedimentation Rates ◽  
Sedimentary Environments ◽  
Faunal Change ◽  
Queen Charlotte Islands ◽  
Global Correlation ◽  
Compensation Depth ◽  
Low Diversity ◽  
Upper Slope ◽  
Carbonate Compensation Depth

Precise comparison of the change in radiolarian faunas 3.5 m above a U–Pb zircon dated 199.6 ± 0.3 Ma tuff and approximately coincident with a negative δ13C anomaly in the Queen Charlotte Islands, B.C. (Canada) with Inuyama (Japan) sequences indicates that major global changes occurred across the Triassic–Jurassic (T–J) boundary. Nearly 20 genera and over 130 Rhaetian species disappeared at the end of the Triassic. The index genera Betraccium and Risella disappear and the final appearance of Globolaxtorum tozeri, Livarella valida, and Pseudohagiastrum giganteum sp. nov. are also diagnostic for the end of the Triassic. The low-diversity Hettangian survival fauna immediately above the boundary is composed mainly of small, primitive spumellarians with spongy or irregularly latticed meshwork and rod-like spines, and new genera Charlottea, Udalia, and Parahsuum s.l. first appear in the lowest Hettangian in both localities. Irrespective of different sedimentation rates and sedimentary environments, such as shelf to upper slope (Queen Charlotte Islands) and deep sea below carbonate compensation depth (CCD; Inuyama), radiolarians show a similar turnover pattern at the T–J boundary.

Recent Rapid Climate Changes in Antarctic and their Influence on Low Diversity Ecosystems

2010 ◽  
Vol 17 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Katarzyna J. Chwedorzewska
Keyword(s):  
Environmental Variables ◽  
Climate Changes ◽  
Biological Significance ◽  
Global Changes ◽  
Factors Affecting ◽  
Low Diversity ◽  
Main Factors ◽  
The Antarctic ◽  
High Diversity ◽  
Temperature Water

ABSTRACTThe geographic position, astronomic factors (e.g. the Earth’s maximum distance from the Sun during winter), ice cover and altitude are the main factors affecting the climate of the Antarctic, which is the coldest place on Earth. Parts of Antarctica are facing the most rapid rates of anthropogenic climate change currently seen on the planet. Climate changes are occurring throughout Antarctica, affecting three major groups of environmental variables of considerable biological significance: temperature, water, UV-B radiation.Low diversity ecosystems are expected to be more vulnerable to global changes than high diversity ecosystems

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 Sedimentary changes on the Southeastern Brazilian upper slope during the last 35,000 years

2007 ◽  
Vol 79 (1) ◽  
pp. 171-181 ◽  
Author(s):  
Michel M. Mahiques ◽  
Marina M. Fukumoto ◽  
Ilson C.A. Silveira ◽  
Rubens C.L. Figueira ◽  
Marcia C. Bícego ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Productivity ◽  
Accumulation Rate ◽  
Climatic Conditions ◽  
Southeastern Brazil ◽  
Sedimentation Rates ◽  
Sedimentary Characteristics ◽  
Brazil Current ◽  
Sedimentary Core ◽  
Upper Slope

A first evaluation of the sedimentary changes, including accumulation of inorganic and organic carbon on the upper slope off Southeastern Brazil under different climatic conditions, based on the analysis of a sedimentary core, is here presented. Results indicate that sedimentation rate as well sedimentary characteristics, including the nature of the organic carbon deposited during the LGM (Last Glacial Maximum), were different from the present deposition, indicating higher primary productivity during the LGM, to be accounted for by the higher values of marine organic carbon. Nevertheless, the higher values of Accumulation Rate of calcium carbonate and organic carbon can be credited to the higher values of the sedimentation rates. Conditions prevailing during Isotope Stage 3 may be considered intermediate as between the LGM and the present day. The conditions for a higher primary productivity associated with the deposition of finer terrigenous sediments may be explained as a response to the off shoreward displacement of the main flow of the Brazil Current.

scholarly journals A comparative study of collections from the S.W. Pacific (Saipan to Tonga), with the descriptions of <i>Gambiella caudata</i> (Brady, 1890) and a new species of <i>Pterobairdia</i> (Ostracoda)

1986 ◽  
Vol 5 (1) ◽  
pp. 91-108 ◽  
Author(s):  
K. G. Mckenzie
Keyword(s):  
New Species ◽  
Comparative Study ◽  
Endemic Species ◽  
Species Level ◽  
Similarity Matrix ◽  
Compensation Depth ◽  
Ecological Importance ◽  
A New Species ◽  
Made In ◽  
Carbonate Compensation Depth

Abstract. Gambiella caudata (Brady, 1890) and Pterobairdia briggsae sp. nov. are described from collections made in the S. W. Pacific (Saipan, Onotoa, Ontong-Java/Kula Gulf, Noumea, Cook Islands, Fiji, Samoa, Tonga); and the lectotypes of several species described in a major early paper by Brady (1890) are illustrated. The carbonate compensation depth in this region lies at around 4500 m. Comparison of the Ontong-Java in Kula Gulf samples reinforces consideration of depth as a factor of ecological importance. A similarity matrix for the several faunas shows factors in common at species level ranging from 22% (Onotoa/Noumea) to nearly 60% (Samoa/Onotoa); while endemism ranges from 8.5% (Samoa) to nearly 33% (Tonga). Most endemic species belong in a limited number of podocopid families, in particular Bairdiidae, Trachyleberididae, Paradoxostomatidae and Leptocytheridae. These results appear consistent with an hypothesis that continued tectonics-driven changes in the regional marine topography and sedimentation, i.e. niche development, could have triggered speciation along the regional plate margins.

Carbonate Compensation Depth: Relation to Carbonate Solubility in Ocean Waters

Science ◽  
1974 ◽  
Vol 184 (4140) ◽  
pp. 982-984 ◽  
Author(s):  
S. Ben-Yaakov ◽  
E. Ruth ◽  
I. R. Kaplan
Keyword(s):  
Compensation Depth ◽  
Carbonate Compensation Depth
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