Magnetostratigraphy of U-Pb–dated boreholes in Svalbard, Norway, implies that magnetochron M0r (a proposed Barremian-Aptian boundary marker) begins at 121.2 ± 0.4 Ma

Geology ◽  
2021 ◽  
Author(s):  
Yang Zhang ◽  
James G. Ogg ◽  
Daniel Minguez ◽  
Mark W. Hounslow ◽  
Snorre Olaussen ◽  
...  
Keyword(s):  
Spreading Rate ◽  
Magnetic Polarity ◽  
Stratigraphic Correlation ◽  
Geologic Time ◽  
Oceanic Spreading ◽  
M Sequence ◽  
Geologic Time Scale ◽  
Age Model ◽  
Oceanic Basalts ◽  
Radioisotopic Dating

The age of the beginning of magnetic polarity Chron M0r, a proposed marker for the base of the Aptian Stage, is disputed due to a divergence of published radioisotopic dates and ambiguities in stratigraphic correlation of sections. Our magnetostratigraphy of core DH1 from Svalbard, Norway, calibrates a bentonite bed, dated by U-Pb methods to 123.1 ± 0.3 Ma, to the uppermost part of magnetozone M1r, which is ~1.9 m.y. before the beginning of Chron M0r. This is the first direct calibration of any high-precision radioisotopic date to a polarity chron of the M sequence. The interpolated age of 121.2 ± 0.4 Ma for the beginning of Chron M0r is younger by ~5 m.y. than its estimated age used in the Geologic Time Scale 2012, which had been extrapolated from radioisotopic dates on oceanic basalts and from Aptian cyclostratigraphy. The adjusted age model implies a commensurate faster average global oceanic spreading rate of ~12% during the Aptian–Santonian interval. Future radioisotopic dating and high-resolution cyclostratigraphy are needed to investigate where to expand the mid-Jurassic to earliest Cretaceous interval by the required ~4 m.y.

Magnetic Properties of Coring Samples from Aceh Basin West Off Sumatera Island

2014 ◽  
Vol 896 ◽  
pp. 434-439
Author(s):  
Eddy Z. Gaffar
Keyword(s):  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Magnetic Polarity ◽  
Isothermal Remanent Magnetization ◽  
Reverse Polarity ◽  
Geologic Time ◽  
The Third ◽  
Geologic Time Scale ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Three oriented core samples was taken by Japanese MIRAI Research Vessel in Aceh Basin west of the Sumatera Island. 927 small box samples from 3 coring samples was measure. Core bottom ages of three cores are in the last glacial maximum (around 19 kyBP). We measured Natural Remanent Magnetization (NRM), NRM after Alternating Field Demagnetization up to 800 Oe. Measurement of NRM have done by 2G Enterprice Squid, Isothermal Remanent Magnetization (IRM) and Anhysteretic Remanent Magnetization (ARM) on Paleomagnetic Laboratory of Geological Survey of Japan. Result of NRM after Alternating Field Demagnetization shows that there are reverse polarizaty magnetizations. This reverse polarity seems not usual since in Geologic Time Scale 1989 showed that the first reversal polarity was between Brunches Normal Epoch and Jaramillo Epoch beginning at 0.75 Ma There are some possibility of reverse polarity events contained in the three cores mentioned above. The first possibility is the result of the tsunami so that the sediment that settles on the Aceh Basin was a sediment that remain turbid flows that enable magnetic recording on magnetic sediment did not follow directions when he formed so that it seems a polarity reverse polarity when only superficial. The second possibility is indeed occurs under reverse polarity at age 700.000 years. Research in Argentina, South America show that between 11 thousand to two thousand years ago there was an excursion from the magnetic polarity produces some reverse polarity at the time (Nami, 1999). The third possibility was circular variation magnetic.

scholarly journals A comparison of two astronomical tuning approaches for the Oligocene-Miocene Transition from Pacific Ocean Site U1334 and implications for the carbon cycle

2017 ◽  
Author(s):  
Helen M. Beddow ◽  
Diederik Liebrand ◽  
Douglas S. Wilson ◽  
Frits J. Hilgen ◽  
Appy Sluijs ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Orbital Eccentricity ◽  
Independent Evidence ◽  
Climate Proxy ◽  
Geologic Time ◽  
Proxy Records ◽  
Astronomical Tuning ◽  
Geologic Time Scale ◽  
Age Model ◽  
Spreading Rates

Abstract. Astronomical tuning of sediment sequences requires both unambiguous cycle-pattern recognition in climate proxy records and astronomical solutions, and independent information about the phase relationship between these two. Here we present two astronomically tuned age models for the Oligocene-Miocene Transition (OMT) from Integrated Ocean Drilling Program Site U1334 (equatorial Pacific Ocean) to assess the effect tuning approaches have on astronomically calibrated ages and the geologic time scale. These age models are based on different phase-assumptions between climate proxy records and eccentricity: the first age model is based on an inverse and in-phase assumption of CaCO3 weight (wt %) to Earth's orbital eccentricity, the second age model is based on an inverse and in-phase assumption of benthic foraminifer stable carbon isotope ratios (δ13C) to eccentricity. The phase-assumptions that underpin these age models represent two end-members on the range of possible tuning options. To independently test which tuned age model and tuning assumptions are correct, we assign their ages to magnetostratigraphic reversals identified in anomaly profiles. Subsequently we compute tectonic plate-pair spreading rates based on the tuned ages. These alternative spreading rate histories indicate that the CaCO3 tuned age model is most consistent with a conservative assumption of constant spreading rates. The CaCO3 tuned age model thus provides robust ages and durations for polarity chrons C6Bn.1n–C6Cn.1r, which are not based on astronomical tuning in the latest iteration of the Geologic Time Scale. Furthermore, it provides independent evidence that the relatively large (several 10,000 years) time lags documented in the benthic foraminiferal isotope records relative to orbital eccentricity, constitute a real feature of the Oligocene-Miocene climate system and carbon cycle. The age constraints from Site U1334 thus provide independent evidence that the delayed responses of the Oligocene-Miocene climate-cryosphere system and carbon cycle resulted from increased nonlinear feedbacks to astronomical forcing.

A Geologic Time Scale 1989. W. B. Harland

1991 ◽  
Vol 99 (5) ◽  
pp. 786-786
Author(s):  
John J. Flynn
Keyword(s):  
Time Scale ◽  
Geologic Time ◽  
Geologic Time Scale

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).

A geologic time scale

2013 ◽  
pp. 476-476
Author(s):  
Frank D. Stacey ◽  
Paul M. Davis
Keyword(s):  
Time Scale ◽  
Geologic Time ◽  
Geologic Time Scale

Plutonium in Crystalline Ceramics and Glasses

MRS Bulletin ◽  
2001 ◽  
Vol 26 (9) ◽  
pp. 698-706 ◽  
Author(s):  
Isabelle Muller ◽  
William J. Weber
Keyword(s):  
Long Range ◽  
Nuclear Waste ◽  
Materials Science ◽  
Ceramic Matrix ◽  
Range Order ◽  
Long Range Order ◽  
Geologic Time ◽  
The Past ◽  
Geologic Time Scale ◽  
High Flexibility

The investigation of plutonium in glasses (amorphous ceramics lacking long-range order), in crystalline ceramics, and in composite materials composed of multiple crystalline or glass and crystalline phases, relieson multidisciplinary studies of physics, chemistry, and materials science. It involves the study of the plutonium atoms in materials with only short-range periodicity, as in glasses, to materials with long-range periodicity, as in crystals. The materials studied over the past 30 years include simple binary crystals, used to investigate the electronic structure of plutonium, to complex glasses and ceramics selected not only for the safety and durability that they provide for the immobilization of nuclear waste and plutonium, but also for the high flexibility they offer in composition. The lack of long-range order at the atomic level in glasses permits the inclusion of abroad range of waste elements, but it renders more difficult the interpretation of data from many commonly used experimental techniques. Regardless of the challenge, much of the research conducted in this field over the past few decades has been motivated by the use of plutonium as a surrogate for all nuclear-waste actinides or on its own in immobilization studies, in order to develop a durable glass or ceramic matrix that can resist leaching and mobilization of the plutonium on a geologic time scale.

Sign in / Sign up

Export Citation Format

Share Document