Recent high-resolution δ 18 O records from North Atlantic (I)ODP cores, with reliable paleomagnet... more Recent high-resolution δ 18 O records from North Atlantic (I)ODP cores, with reliable paleomagnetic signals, have placed the mean age of the Matuyama-Brunhes (MB) geomagnetic polarity reversal ca. 8 ka younger than previous estimates when correlated to ice-volume age models ( ...
ABSTRACT The Bishop Tuff forms a key stratigraphic horizon for synchronization of Quaternary sedi... more ABSTRACT The Bishop Tuff forms a key stratigraphic horizon for synchronization of Quaternary sedimentary records in North America. The unit stratigraphically overlies the Matuyama-Bruhnes geomagnetic polarity reversal by several thousand years; high precision dating of this tuff may be valuable for regional and global correlation of records. The Quaternary time scale is anchored by 40Ar/39Ar ages on lava flows and ash layers where available [e.g., Singer, 2013], with stage boundaries and geomagnetic reversals including astronomically tuned records [Gradstein et al., 2012]. However, astronomical dating has not yet validated the high precision 238U/206Pb zircon and 40Ar/39Ar sanidine ages of the Bishop Tuff. We have identified the Bishop Tuff within the marine sedimentary record, and derived an astronomical age of 0.765 ± 0.008 Ma by correlation to the LR04 δ18O global benthic stack and its age model. This age is consistent with Bishop Tuff radio-isotopic ages, including new single crystal 40Ar/39Ar sanidine fusion analyses presented here, which demonstrates that concordance through multiple dating techniques is achievable within the Quaternary.
Deep marine successions of early Campanian age from DSDP (Deep Sea Drilling Project) site 516F dr... more Deep marine successions of early Campanian age from DSDP (Deep Sea Drilling Project) site 516F drilled at low paleolatitudes in the South Atlantic reveal distinct sub-Milankovitch variability in addition to precession, obliquity and eccentricity-related variations. Elemental abundance ratios point to a similar climatic origin for these variations and exclude a quadripartite structure as an explanation for the inferred semi-precession cyclicity in the magnetic susceptibility (MS) signal as observed in the Mediterranean Neogene for precession-related cycles. However, semi-precession cycles as suggested by previous work are likely an artifact reflecting the first harmonic of the precession signal. The sub-Milankovitch variability, especially in MS, is best approximated by a ∼ 7 kyr cycle as shown by spectral analysis and bandpass filtering. The presence of sub-Milankovitch cycles with a period similar to that of Heinrich events of the last glacial cycle is consistent with linking the latter to low-latitude climate change caused by a non-linear response to precession-induced variations in insolation between the tropics.
Abstract-A high-resolution palaeomagnetic intensity study of 160 discrete samples from an archaeo... more Abstract-A high-resolution palaeomagnetic intensity study of 160 discrete samples from an archaeological excavation near Piatra Neamt (Romania) gives the opportunity to compare the palaeointensity signal from this sequence to reference data from sites with established ...
Palaeomagnetic investigations were carried out at the archaeological site of Poiana Cireş ului (R... more Palaeomagnetic investigations were carried out at the archaeological site of Poiana Cireş ului (Romania) to check whether the loess records a reliable palaeomagnetic signal, and to compare this signal to reference data. The sediments are composed of loess and loess-like sediments. Pedogenic alterations and a pronounced cultural layer occur in the section. The archaeology-bearing sedimentary geoarchive spans the time interval from ca. 20 to ca. 55 ka, and was dated mainly by 14 C and luminescence techniques. The record of geomagnetic palaeosecular variation from this European loess site is discussed. The presented palaeomagnetic record bears analogies to data from Lac du Bouchet (France), and is a reliable high resolution record (mean sedimentation rates are ca. 20 cm/ky) of palaeosecular variation. The results imply that European loess geoarchives may record palaeosecular variation features, even if loess is (pedogenically) altered. The palaeosecular variation pattern of loess is here employed as a stratigraphic tool.
Recent high-resolution δ 18 O records from North Atlantic (I)ODP cores, with reliable paleomagnet... more Recent high-resolution δ 18 O records from North Atlantic (I)ODP cores, with reliable paleomagnetic signals, have placed the mean age of the Matuyama-Brunhes (MB) geomagnetic polarity reversal ca. 8 ka younger than previous estimates when correlated to ice-volume age models ( ...
ABSTRACT The Bishop Tuff forms a key stratigraphic horizon for synchronization of Quaternary sedi... more ABSTRACT The Bishop Tuff forms a key stratigraphic horizon for synchronization of Quaternary sedimentary records in North America. The unit stratigraphically overlies the Matuyama-Bruhnes geomagnetic polarity reversal by several thousand years; high precision dating of this tuff may be valuable for regional and global correlation of records. The Quaternary time scale is anchored by 40Ar/39Ar ages on lava flows and ash layers where available [e.g., Singer, 2013], with stage boundaries and geomagnetic reversals including astronomically tuned records [Gradstein et al., 2012]. However, astronomical dating has not yet validated the high precision 238U/206Pb zircon and 40Ar/39Ar sanidine ages of the Bishop Tuff. We have identified the Bishop Tuff within the marine sedimentary record, and derived an astronomical age of 0.765 ± 0.008 Ma by correlation to the LR04 δ18O global benthic stack and its age model. This age is consistent with Bishop Tuff radio-isotopic ages, including new single crystal 40Ar/39Ar sanidine fusion analyses presented here, which demonstrates that concordance through multiple dating techniques is achievable within the Quaternary.
Deep marine successions of early Campanian age from DSDP (Deep Sea Drilling Project) site 516F dr... more Deep marine successions of early Campanian age from DSDP (Deep Sea Drilling Project) site 516F drilled at low paleolatitudes in the South Atlantic reveal distinct sub-Milankovitch variability in addition to precession, obliquity and eccentricity-related variations. Elemental abundance ratios point to a similar climatic origin for these variations and exclude a quadripartite structure as an explanation for the inferred semi-precession cyclicity in the magnetic susceptibility (MS) signal as observed in the Mediterranean Neogene for precession-related cycles. However, semi-precession cycles as suggested by previous work are likely an artifact reflecting the first harmonic of the precession signal. The sub-Milankovitch variability, especially in MS, is best approximated by a ∼ 7 kyr cycle as shown by spectral analysis and bandpass filtering. The presence of sub-Milankovitch cycles with a period similar to that of Heinrich events of the last glacial cycle is consistent with linking the latter to low-latitude climate change caused by a non-linear response to precession-induced variations in insolation between the tropics.
Abstract-A high-resolution palaeomagnetic intensity study of 160 discrete samples from an archaeo... more Abstract-A high-resolution palaeomagnetic intensity study of 160 discrete samples from an archaeological excavation near Piatra Neamt (Romania) gives the opportunity to compare the palaeointensity signal from this sequence to reference data from sites with established ...
Palaeomagnetic investigations were carried out at the archaeological site of Poiana Cireş ului (R... more Palaeomagnetic investigations were carried out at the archaeological site of Poiana Cireş ului (Romania) to check whether the loess records a reliable palaeomagnetic signal, and to compare this signal to reference data. The sediments are composed of loess and loess-like sediments. Pedogenic alterations and a pronounced cultural layer occur in the section. The archaeology-bearing sedimentary geoarchive spans the time interval from ca. 20 to ca. 55 ka, and was dated mainly by 14 C and luminescence techniques. The record of geomagnetic palaeosecular variation from this European loess site is discussed. The presented palaeomagnetic record bears analogies to data from Lac du Bouchet (France), and is a reliable high resolution record (mean sedimentation rates are ca. 20 cm/ky) of palaeosecular variation. The results imply that European loess geoarchives may record palaeosecular variation features, even if loess is (pedogenically) altered. The palaeosecular variation pattern of loess is here employed as a stratigraphic tool.
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