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Форум сайта JURASSIC.RU » Ссылки и информация » Интересные ссылки » Страничка Christopher A. McRoberts (и много статей по границе триаса и юры)
Страничка Christopher A. McRoberts
mhornДата: Понедельник, 12.10.2009, 18:36 | Сообщение # 1
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Страничка известного триасовика, который заодно изучает и границу триаса с юрой
Зовут его Christopher A. McRoberts, вот заглавная страница сайта: http://paleo.cortland.edu/mcroberts/INDEX.HTML
а вот - список публикаций со ссылками на пдфы: http://paleo.cortland.edu/mcroberts/#publications

в том числе выложены вот такие статьи:

Ward P., Garrison G., Williford K., Kring D., Goodwin D., Beattie M., McRoberts C. A. (2007) The organic carbon isotopic and paleontological record across the Triassic-Jurassic boundary at the candidate GSSP section at Ferguson Hill, Muller Canyon, Nevada, USA // In Hesselbo, S. P., McRoberts, C. A., and Pálfy, J., eds., Special Issue: Triassic-Jurassic Boundary Events: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 244. pp. 281-289.
pdf: http://paleo.cortland.edu/mcroberts/documents/Ward_et_al_2007.pdf
We present new litho-, bio-, and chemostratigraphic data from the Triassic–Jurassic (T–J) boundary section at Ferguson Hill (Muller Canyon), Nevada, USA. This section is a candidate for the base of the Hettangian Stage and thus the T–J boundary. Our measurements yield a 19 m thickness for the Muller Canyon Member of the Gabbs Formation. We recognize the Triassic–Jurassic boundary using the first appearance of Agerchlamys, and place it 9.6 m above the boundary between the Muller Canyon Member and the subjacent Mount Hyatt Member, with the first occurrence of the ammonite Psiloceras tilmanni occurring 0.9 m above this. Our organic carbon isotope record from this section shows two excursions toward lighter values, one at the T–J boundary, and the second in the lower parts of the Jurassic Sunrise Formation. These results are significantly different from a prior report on light stable isotopes from this section.

Yin J., McRoberts C.A. (2006) Latest Triassic-Earliest Jurassic bivalves of the Germig Formation from Lanongla (Tibet, China) // Journal of Paleontology, vol. 80, no. 1, pp. 104-120.
pdf: http://paleo.cortland.edu/mcroberts/McRobertsFiles/YinMcRoberts_06.pdf
The Germig Formation of the Tethyan Himalaya of southern Tibet contains an exceptionally abundant bivalve fauna which has been found in association with choristoceratid and psiloceratid ammonoids and spans the Triassic/Jurassic boundary. The bivalve fauna consists of 25 species, including four new species: Newaagia lanonglaensis, Persia hallami, Liostrea tibetica, and Ctenostreon newelli. The fauna comprises three biostratigraphically controlled bivalve assemblages: 1) an upper Rhaetian Palaeocardita–Krumbeckiella Assemblage including seven species; 2) a high diversity transitional Rhaetian-Hettangian Persia–Plagiostoma Assemblage with many as 19 species; and 3) a low diversity lower Hettangian Liostrea–Chlamys Assemblage containing three species. The transitional Rhaetian-Hettangian Assemblage is dominated by cementing species and exhibits a high degree of endemism. A large proportion of lower latitude and cementing taxa from the lower two levels may indicate that they inhabited shallow subtidal tropic or subtropic paleoenvironments.

Schaltegger U., Guex J., Bartolini A., Schoene B., Ovtcharova M. (2008) Precise U–Pb age constraints for end-Triassic mass extinction, its correlation to volcanism and Hettangian post-extinction recovery // Earth and Planetary Science Letters. V.267. P.266–275.
Pdf: http://www.princeton.edu/geoscie....L08.pdf
New precise zircon U–Pb ages are proposed for the Triassic–Jurassic (Rhetian–Hettangian) and the Hettangian–Sinemurian boundaries. The ages were obtained by ID-TIMS dating of single chemical-abraded zircons from volcanic ash layers within the Pucara Group, Aramachay Formation in the Utcubamba valley, northern Peru. Ash layers situated between last and first occurrences of boundary-defining ammonites yielded 206Pb/238U ages of 201.58±0.17/0.28 Ma (95% c.l., uncertainties without/with decay costant errors, respectively) for the Triassic–Jurassic and of 199.53±0.19 / 0.29 Ma for the Hettangian–Sinemurian boundaries. The former is established on a tuff located 1 m above the last local occurrence of the topmost Triassic genus Choristoceras, and 5 m below the Hettangian genus Psiloceras. The latter sample was obtained from a tuff collected within the Badouxia canadensis beds. Our new ages document total duration of the Hettagian of no more than c. 2 m.y., which has fundamental implications for the interpretation and significance of the ammonite recovery after the topmost Triassic extinction. The U–Pb age is about 0.8±0.5% older than 40Ar–39Ar dates determined on flood basalts of the Central Atlantic Magmatic Province (CAMP). Given the widely accepted hypothesis that inaccuracies in the 40K decay constants or physical constants create a similar bias between the two dating methods, our new U–Pb zircon age determination for the T/J boundary corroborates the hypothesis that the CAMP was emplaced at the same time and may be responsible for a major climatic turnover and mass extinction. The zircon 206Pb/238U age for the T/J boundary is marginally older than the North Mountain Basalt (Newark Supergroup, Nova Scotia, Canada), which has been dated at 201.27±0.06 Ma [Schoene et al., 2006. Geochim. Cosmochim. Acta 70, 426–445]. It will be important to look for older eruptions of the CAMP and date them precisely by U–Pb techniques while addressing all sources of systematic uncertainty to further test the hypothesis of volcanic induced climate change leading to extinction. Such high-precision, high-accuracy data will be instrumental for constraining the contemporaneity of geological events at a 100 kyr level.
(в последней статье кроме всего ещё и изображено энное количество аммонитов)


верхнеюрские и нижнемеловые аммониты и всё что с ними связано
 
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