Using radiometric ages to develop conventional ageing methods for shortraker rockfish (Sebastes borealis)

2007 ◽  
Author(s):  
C.E. Hutchinson ◽  
C.R. Kastelle ◽  
D.K. Kimura ◽  
D.R. Gunderson
Keyword(s):  
Radiometric Ages ◽  
Ageing Methods

Potassium–Argon Ages of Igneous Rocks from the Area near Hedley, Southern British Columbia

1972 ◽  
Vol 9 (12) ◽  
pp. 1632-1639 ◽  
Author(s):  
J. C. Roddick ◽  
E. Farrar ◽  
E. L. Procyshyn
Keyword(s):  
British Columbia ◽  
Igneous Rocks ◽  
Magmatic Activity ◽  
Radiometric Ages

K–Ar ages are reported for 19 samples collected from the Hedley, Okanagan, and Similkameen Complexes located in the vicinity of Hedley, British Columbia. Although the zoned nature of amphiboles collected from the Hedley Complex makes interpretation of their radiometric ages difficult, it is suggested that the Hedley Complex was intruded at least 165 m.y. ago and was a part of the same magmatic activity that gave rise to both the Okanagan and Similkameen batholithic complexes. These latter complexes yield ages ranging from 141 m.y. to 184 m.y.

African Homo erectus: old radiometric ages and young Oldowan assemblages in the Middle Awash Valley, Ethiopia

Science ◽  
1994 ◽  
Vol 264 (5167) ◽  
pp. 1907-1910 ◽  
Author(s):  
J. Clark ◽  
J de Heinzelin ◽  
K. Schick ◽  
W. Hart ◽  
T. White ◽  
...  
Keyword(s):  
Homo Erectus ◽  
Middle Awash ◽  
Radiometric Ages

The use of high-resolution stratigraphy and derived lithoclasts to document structural inversion; a case study from the Paleogene, Isle of Wight, U.K.

2021 ◽  
pp. jgs2020-156
Author(s):  
Andy Gale
Keyword(s):  
The West ◽  
North West ◽  
Geologic Time ◽  
Northern Limb ◽  
The North ◽  
Basement Faults ◽  
Structural Inversion ◽  
Geologic Time Scale ◽  
Radiometric Ages

The effects of structural inversion, generated by the Pyrenean Orogeny on the southerly bounding faults of the Hampshire Basin (Needles and Sandown Faults) on Eocene sedimentation in the adjacent regions were studied in outcrops by sedimentary logging, dip records and the identification of lithoclasts reworked from the crests of anticlines generated during inversion. The duration and precise age of hiatuses associated with inversion was identified using bio- and magnetostratigraphy, in comparison with the Geologic Time Scale 2020. The succession on the northern limb of the Sandown Anticline (Whitecliff Bay) includes five hiatuses of varying durations which together formed a progressive unconformity developed during the Lutetian to Priabonian interval (35-47Ma). Syn-inversion deposits thicken southwards towards the southern margin of the Hampshire Basin and are erosionally truncated by unconformities. The effects of each pulse of inversion are recorded by successively shallower dips and the age and nature of clasts reworked from the crest of the Sandown Anticline. Most individual hiatuses are interpreted as minor unconformities developed subsequent to inversion, rather than eustatically-generated sequence boundaries:transgressive surfaces. In contrast, the succession north of the Needles Fault (Alum Bay) does not contain hiatuses of magnitude or internal unconformities. In the north-west of the island, subsidiary anticlinal and synclinal structures developed in response to Eocene inversion events by the reactivation of minor basement faults. The new dates of the Eocene inversion events correspond closely with radiometric ages derived from fracture vein-fill calcites in Dorset, to the west (36-48Ma).

scholarly journals Paleomagnetic secular variation for a 21,000-year sediment sequence from Cascade Lake, north-central Brooks Range, Arctic Alaska

2021 ◽  
Author(s):  
Douglas P. Steen ◽  
Joseph S. Stoner ◽  
Jason P. Briner ◽  
Darrell S. Kaufman
Keyword(s):  
Secular Variation ◽  
Remanent Magnetization ◽  
Sediment Cores ◽  
Natural Remanent Magnetization ◽  
Companion Paper ◽  
Angular Deviation ◽  
Arctic Alaska ◽  
Geomagnetic Field Models ◽  
Paleomagnetic Secular Variation ◽  
Radiometric Ages

Abstract. Two > 5-m-long sediment cores from Cascade Lake (68.38° N, 154.60° W), Arctic Alaska, were analyzed to quantify their paleomagnetic properties over the past 21,000 years. Alternating-field demagnetization of the natural remanent magnetization, anhysteretic remanent magnetization, isothermal remanent magnetization, and hysteresis experiments reveal a strong, well-defined characteristic remanent magnetization carried by a low coercivity magnetic component that increases up core. Maximum angular deviation values average < 2°, and average inclination values are within 4° of the geocentric axial dipole prediction. Radiometric ages based on 210Pb and 14C were used to correlate the major inclination features of the resulting paleomagnetic secular variation (PSV) record with those of other regional PSV records, including two geomagnetic field models and the longer series from Burial Lake, located 200 km to the west. Following around 6 ka (cal BP), the ages of PSV fluctuations in Cascade Lake begin to diverge from those of the regional records, reaching a maximum offset of about 2000 years at around 4 ka. Several correlated cryptotephra ages from this section (reported in a companion paper by Davies et al., this volume) support the regional PSV-based chronology and indicate that some of the 14C ages at Cascade Lake are variably too old.

scholarly journals Age of the Post-rift Sequence I from the Araripe Basin, Lower Cretaceous, NE Brazil: implications for spatio-temporal correlation

2021 ◽  
Vol 24 (1) ◽  
pp. 37-46
Author(s):  
João Carlos Coimbra ◽  
Tiago Menezes Freire
Keyword(s):  
Critical Review ◽  
Lower Cretaceous ◽  
Temporal Correlation ◽  
Isotopic Analysis ◽  
The Other ◽  
Stratigraphic Framework ◽  
Spatio Temporal ◽  
Radiometric Ages ◽  
The One ◽  
Do So

A robust biostratigraphic zonation based on microfossils supports the stratigraphic framework and correlation of the interior basins of the Lower Cretaceous of NE Brazil. This zonation has also allowed correlations with coeval sections in the Brazilian marginal basins and in the Gabon and Congo basins (central-west Africa). These records, consisting mainly of non-marine sediments, were a great challenge with regard to the correlation with the International Chronostratigraphic Chart. Therefore, local stages were used, the most recent being the Alagoas local Brazilian Stage, with which the Post-rift Sequence I of the Araripe Basin is related. Regarding lithostratigraphy, this sequence includes the Rio da Batateira (Barbalha for some authors) and Santana formations, the last one with the famous Crato, Ipubi, and Romualdo members, from the base to the top. Although currently there is a consensus on the age of the Alagoas local Brazilian Stage in the Araripe Basin, recently a new age for at least part of the Post-rift Sequence I was proposed. This new proposal, based on isotopic analysis of Re-Os, arose as a panacea to correlate the Rio da Batateira Formation and the Crato and Ipubi members with the international stages. Surprisingly, their authors, although on the one hand, they seem to underestimate biostratigraphic results, on the other they seek to support their proposal from microfossils studied by previous authors, but they do so in an inappropriate way, leading readers to misinterpret their results. Therefore, this paper presents a critical review on the age of the Alagoas local Brazilian Stage in the Araripe Basin and nearby basins, refuting a Barremian age for part of the Post-rift Sequence I. Keywords: Alagoas local Brazilian Stage, biostratigraphy, ostracods, palynomorphs, radiometric ages.

An explanation for low radiometric ages from glauconite

1973 ◽  
Vol 37 (6) ◽  
pp. 1473-1491 ◽  
Author(s):  
Graham R. Thompson ◽  
John Hower
Keyword(s):  
Radiometric Ages

Arguments for the Age of Serpent Mound

2018 ◽  
Vol 28 (3) ◽  
pp. 433-450 ◽  
Author(s):  
Bradley T. Lepper ◽  
James R. Duncan ◽  
Carol Diaz-Granádos ◽  
Tod A. Frolking
Keyword(s):  
Cultural Context ◽  
Close Association ◽  
Oral Traditions ◽  
Fort Ancient ◽  
Alternative Means ◽  
Radiometric Ages ◽  
Original Construction ◽  
Original Configuration

Serpent Mound, in northern Adams County, Ohio, USA, is one of the most iconic symbols of ancient America and yet there is no widely agreed upon date for the age of its original construction. Some archaeologists consider it to have been built by the Adena culture around 300bc, while others contend it was built by the Fort Ancient culture aroundad1100. There have been three attempts to obtain radiometric ages for the effigy, but they have yielded inconclusive results. The iconography of the earthwork offers an alternative means of placing the mound in its cultural context. Serpent imagery is abundant in the Fort Ancient culture as well as in the more encompassing Mississippian Ideological Interaction Sphere. Pictographs from Picture Cave in Missouri include a serpent, a humanoid female and a vulvoid in close association. We interpret these elements, in the light of Siouan oral traditions, as First Woman and her consort the Great Serpent. The Picture Cave imagery dates to betweenad950 and 1025. We argue that these same three elements are represented in the original configuration of Serpent Mound and therefore situate its design and original construction in the Early Fort Ancient period.

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