scholarly journals Cross-continental age calibration of the Jurassic/Cretaceous boundary

2018 ◽  
Author(s):  
Luis Lena ◽  
Rafael López-Martínez ◽  
Marina Lescano ◽  
Beatriz Aguirre-Urrreta ◽  
Andrea Concheyro ◽  
...  
Keyword(s):  
High Precision ◽  
Sedimentary Basins ◽  
Minimum Duration ◽  
Zircon Age ◽  
The Past ◽  
Age Determinations ◽  
Tithonian Stage

Abstract. The age of the Jurassic/Cretaceous boundary has remained elusive for the past decades. In this study we evaluate how well the determined boundary age agrees between two distinct sections from different sedimentary basins, and whether we can constrain a globally valid Jurassic/Cretaceous boundary age. Here we present high-precision U-Pb zircon age determinations on single grains of volcanic zircon of two sections that span the Jurassic/Cretaceous: the Las Loicas section, Argentina, and the Mazatepec section in Mexico. These two sections display well-established primary and secondary stratigraphic markers as well as interbedded volcanic horizons that allow bracketing the age of the Jurassic/Cretaceous boundary at 140.22 ± 0.13 Ma. We also present the first age determinations in the early Tithonian and tentatively propose a minimum duration of ~ 7 Ma for the Tithonian stage.

scholarly journals High-precision U–Pb ages in the early Tithonian to early Berriasian and implications for the numerical age of the Jurassic–Cretaceous boundary

Solid Earth ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Luis Lena ◽  
Rafael López-Martínez ◽  
Marina Lescano ◽  
Beatriz Aguire-Urreta ◽  
Andrea Concheyro ◽  
...  
Keyword(s):  
High Precision ◽  
Volcanic Ash ◽  
Sedimentary Basins ◽  
Geochronological Data ◽  
Minimum Duration ◽  
Sierra Madre Oriental ◽  
Sierra Madre ◽  
Neuquen Basin ◽  
Neuquén Basin ◽  
Age Determinations

Abstract. The numerical age of the Jurassic–Cretaceous boundary has been controversial and difficult to determine. In this study, we present high-precision U–Pb geochronological data around the Jurassic–Cretaceous boundary in two distinct sections from different sedimentary basins: the Las Loicas, Neuquén Basin, Argentina, and the Mazatepec, Sierra Madre Oriental, Mexico. These two sections contain primary and secondary fossiliferous markers for the boundary as well as interbedded volcanic ash horizons, allowing researchers to obtain new radioisotopic dates in the late Tithonian and early Berriasian. We also present the first age determinations in the early Tithonian and tentatively propose a minimum duration for the stage as a cross-check for our ages in the early Berriasian. Given our radioisotopic ages in the early Tithonian to early Berriasian, we discuss implications for the numerical age of the boundary.

Episodic tectono-thermal activity in the southern part of the East Greenland Caledonides

2000 ◽  
pp. 42-49 ◽  
Author(s):  
A. Graham Leslie ◽  
Allen P. Nutman
Keyword(s):  
Thermal Activity ◽  
Isotopic Data ◽  
Zircon Age ◽  
East Greenland ◽  
Original Series ◽  
Age Determinations

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Leslie, A. G., & Nutman, A. P. (2000). Episodic tectono-thermal activity in the southern part of the East Greenland Caledonides. Geology of Greenland Survey Bulletin, 186, 42-49. https://doi.org/10.34194/ggub.v186.5214 _______________ Isotopic data from the Renland augen granites of the Scoresby Sund region (Figs 1, 2) provided some of the first convincing support for relicts of potentially Grenvillian tectono-thermal activity within the East Greenland Caledonides. In Renland, Chadwick (1975) showed the presence of major bodies of augen granite (Fig. 2) interpreted by Steiger et al. (1979), on the basis of Rb–Sr whole rock and U–Pb zircon age determinations, to have been emplaced about 1000 Ma ago.

CANADIAN STANDARD OF FREQUENCY

1959 ◽  
Vol 37 (1) ◽  
pp. 10-18 ◽  
Author(s):  
S. N. Kalra ◽  
C. F. Pattenson ◽  
M. M. Thomson
Keyword(s):  
High Precision ◽  
Phase Measurement ◽  
Frequency Standard ◽  
Frequency Stability ◽  
Absolute Frequency ◽  
Standard Frequency ◽  
Astronomical Observations ◽  
The Past ◽  
Time Signals ◽  
Very High

Over the past 3 years a frequency standard of very high precision has been installed in Canada. It is composed of equipment located in three different laboratories in Ottawa, Ontario, but separated by a few miles. Intercomparison of frequency between these laboratories, which is done by sending signals over telephone lines and related techniques, is briefly described. Results indicate frequency stability of about 2:1010 over short and long periods. Absolute frequency is determined from astronomical observations. International inter-comparison is carried out by phase measurement of standard frequency and by observations of time signals; some of the results are presented.

Introduction to aspects of economics and logistics

1978 ◽  
Vol 290 (1366) ◽  
pp. 3-19 ◽  
Keyword(s):  
Capital Investment ◽  
Sedimentary Basins ◽  
Economic Implications ◽  
High Productivity ◽  
Capital Costs ◽  
Oil Companies ◽  
The Past ◽  
Codes Of Practice ◽  
Financial Arrangements ◽  
Exploration And Development

During the past five years the oil industry has moved its exploration and development programmes into progressively deeper waters, so that production operations in 150 m (500 feet) of water are becoming conventional, and exploration in water depths of over 300 m (1000 feet) commonplace. The first part of this introductory paper is devoted to areas of opportunity in the deeper waters of the sedimentary basins of the world, with particular emphasis on the technical merits of these areas, and the size and high productivity necessary to justify their development. A description follows of the trend in licensing terms, the tax and financial arrangements that might apply, and the growing involvement of national oil companies and national energy policies with their consequent effect on the control of developments, right to export oil, and the division of profits. The increasing importance of logistic and environmental factors on the technological requirements both in exploration and development is outlined, and some examples drawn of their political and sociological impacts. The development of supporting infrastructure in remote environments, of national preference for materials and services, codes of practice and further constraints in the overall capital investment programmes, are also outlined. The final section deals with the economic implications of these international activities where during the course of the next 25 years it is expected that offshore oil production rates will double. The nature of the risk investments where exploration wells now cost between £3 and £5 M each, and capital costs for individual projects are over £1000 M, are examined, reflecting differences between the private sector objectives and national oil company objectives. Examples can be drawn from events in O.P.E.C. areas during the past five years.

scholarly journals Granitoid plutons in peri-Gondwanaan terranes of Cape Breton Island, Nova Scotia, Canada: new U-Pb (zircon) age constraints

2018 ◽  
pp. 021-080 ◽  
Author(s):  
Sandra M. Barr ◽  
Deanne Van Rooyen ◽  
Chris E. White
Keyword(s):  
Tectonic Setting ◽  
Magmatic Activity ◽  
Zircon Age ◽  
Cape Breton Island ◽  
The Past ◽  
Late Cambrian ◽  
Cape Breton ◽  
History Of ◽  
Tectonic Settings ◽  
Age Constraints

Granitoid plutons are a major component of pre-Carboniferous rocks in Cape Breton Island and knowledge of the time and tectonic setting of their emplacement is crucial for understanding the geological history of the island, guiding exploration for granite-related economic mineralization, and making along-orogen correlations. The distribution of these plutons and their petrological characteristics have been used in the past for recognizing both Laurentian and peri-Gondwanan components in Cape Breton Island, and for subdividing the peri-Gondwanan components into Ganderian and Avalonian terranes. However, ages of many plutons were assumed on the basis of field relations and petrological features compared to those of the relatively few reliably dated plutons. Seventeen new U–Pb (zircon) ages from igneous units reported here provide enhanced understanding of the distribution of pluton ages. Arc-related plutons in the Aspy terrane with ages of ca. 490 to 475 Ma likely record the Penobscottian tectonomagmatic event recognized in the Exploits subzone of central Newfoundland and New Brunswick but not previously recognized in Cape Breton Island. Arc-related Devonian plutonic activity in the same terrane is more widespread, continuous, and protracted (445 Ma to 395 Ma) than previously known. Late Devonian magmatism in the Ganderian Aspy terrane is similar in age to that in the Avalonian Mira terrane (380 to 360 Ma) but the tectonic settings are different. In contrast, magmatic activity in the Bras d’Or terrane is almost exclusively arc-related in the Late Ediacaran (580 to 540 Ma) and rift-related in the Late Cambrian (520 to 490 Ma). The new data support the terrane distinctions previously documented.

scholarly journals Supplemental Material: Detrital zircon geochronology and Hf isotope geochemistry of Mesozoic sedimentary basins in south-central Alaska: Insights into regional sediment transport, basin development, and tectonics along the NW Cordilleran margin

2020 ◽  
Author(s):  
C.R. Fasulo ◽  
et al.
Keyword(s):  
Detrital Zircon ◽  
Isotope Geochemistry ◽  
Age Distribution ◽  
Sedimentary Basins ◽  
Alaska Range ◽  
Zircon Age ◽  
Detrital Zircon Geochronology ◽  
South Central ◽  
Cordilleran Margin ◽  
Detrital Zircon Ages

Supplemental Figure S1. Normalized distribution plot of detrital zircon ages from the Kahiltna assemblage of the central Alaska Range (Hampton et al., 2010), the Wellesly basin (this study), and the Kahiltna assemblage of the northwestern Talkeetna Mountains (Hampton et al., 2010). Note that the detrital zircon age distribution of ages older than 500 Ma has 10× vertical exaggeration.

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