Geochemical indications for the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM-2) hyperthermals in terrestrial sediments of the Canadian Arctic

During the late Paleocene to early Eocene, clastic fluvial sediments and coals were deposited in northern high latitudes as part of the Marga­ret Formation at Stenkul Fiord (Ellesmere Island, Nunavut, Canada). Syn-sedimentary tectonic movements of the Eurekan deformation continu­ously affected these terrestrial sediments. Different volcanic ash layers occur, and unconformities subdivide the deposits into four sedimentary units. Rare vertebrate fossils indicate an early Eocene (Graybullian) age for the upper part of the Stenkul Fiord outcrop. Here, we present carbon isotope data of bulk coal, related organic-rich mud and siltstones, a plant leaf wax-derived alkane, and additional plant remains. These data provide a complete carbon isotope record of one stratigraphic section with defined unconformity positions and in relation to other Eurekan deformation features. A previously dated ash layer MA-1 provided a U-Pb zircon age of 53.7 Ma and is used as a stratigraphic tie point, together with a discrete negative carbon isotope excursion found above MA-1 in a closely sampled coal seam. The excursion is identified as the likely expression of the I-1 hyperthermal event. Based on our isotope data that reflect the early Eocene dynamics of the carbon cycle, this tie point, and previous paleontological constraints from vertebrate fossils, the locations of the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM-2) hyperthermals and their extent along the complete section are herein identified. Within the intervals of the PETM and ETM-2 hyperthermal events, increasing amounts of clastic sediments reached the site toward the respective end of the event. This is interpreted as a response of the fluvial depositional system to an intensified hydrological system during the hyperthermal events. Our study establishes an enhanced stratigraphic framework allowing for the calcula­tion of average sedimentation rates of different intervals and considerations on the completeness of the stratigraphic record. As one of the few high-latitude outcrops of early Eocene terrestrial sediments, the Stenkul Fiord location offers further possibilities to study the effects of extreme warming events in the Paleogene.

Manifestation of the Late Famennian Dasberg Event in the shelf-batial transition (Pai-Khoi sequences)

Research subject. Regional manifestations of the Dasberg eustatic event in the shelf and bathyal Pai-Khoi successions. The event appears in the Lower-Middle expansa zones interval (Upper Devonian, Famennian).Aim. To evaluate the manifestations of the event in the realm of transition from the shallow-water shoal succession of the Pai-Khoi carbonate parautokhtone towards the deep-water (bathyal) successions of the Kara shale allokhtone.Materials and methods. A number of successions comprising different facies and located in different parts of Pai-Khoi were studied: the Silova-Yakha River section and Tal’beyshor Creek section (south-western Pai-Khoi), the Lymbad’yakha section and the Peschanaya River section (northern Pai-Khoi). The interpretation of facies and the reconstruction of transgression-regression couplets were conducted based on the previously developed models of shoal and bathyal sedimentation. The stratigraphic framework comprised data on conodonts, transgression acmes, and carbonate carbon isotopic record.Results. The Pai-Khoi successions comprising Lower–Middle expansa zones demonstrate four transgression-regression cycles. The transgression acme of the third cycle marks the Dasberg eustatic event. The absence of anoxia is characteristic of this event in the region under consideration. The carbonate carbon isotope record of the Silova-Yakha River section shows a structure similar to that of North American successions. Variations in δ13Cкарб were likely to be caused by climate changes and perturbations of the global oceanic circulation.Conclusions. The stratigraphic interval comprising Lower–Middle expansa or Lower–Upper expansa (expansa s. l.) zones is detected clearly in different facies. A more detailed subdivision and correlation in the region under consideration is possible on the basis of evaluating manifestations of the Dasberg eustatic event: a characteristic eustatic succession and variations of the carbonate carbon isotopic composition.

New Chronostratigraphic Constraints on the Lower Jurassic Pliensbachian–Toarcian Boundary at Chacay Melehue (Neuquén Basin, Argentina)

The Pliensbachian–Toarcian boundary interval is characterized by a ~3‰ negative carbon-isotope excursion (CIE) in organic and inorganic marine and terrestrial archives from sections in Europe, such as Peniche (Portugal) and Hawsker Bottoms, Yorkshire (UK). A new high-resolution organic-carbon isotope record, illustrating the same chemostratigraphic feature, is presented from the Southern Hemisphere Arroyo Chacay Melehue section, Chos Malal, Argentina, corroborating the global significance of this disturbance to the carbon cycle. The negative carbon-isotope excursion, mercury and organic-matter enrichment is accompanied by high-resolution ammonite and nannofossil biostratigraphy together with U-Pb CA-ID-TIMS geochronology derived from intercalated volcanic ash beds. A new age of ~183.71 ± 0.40/-0.51 Ma for the Pliensbachian–Toarcian boundary, and 182.77 +0.11/-0.21 for the tenuicostatum–serpentinum zonal boundary, is assigned based on high-precision U-Pb zircon geochronology and a Bayesian Markov chain Monte Carlo (MCMC) stratigraphic age model.

High-Resolution Water Stable Isotope Ice-Core Record: Roosevelt Island, Antarctica

<p>This thesis presents a water-isotope (δD) record from 1900 to 2009 for the Roosevelt Island Climate Evolution (RICE) ice core, Antarctica. Examination of the RICE isotope record with observation data (using global reanalysis and SST datasets) revealed details of the climate signal that is preserved within the full 763 m isotope record. RICE δD provides a proxy record, which captures the central tropical Pacific ENSO variability, the significant (p < 0.01) central Pacific δD-SST correlation pattern contain the Niño-4 SST region. Central tropical Pacific ENSO variability projects upon the Amundsen Sea region via a Pacific–South American pattern (PSA)-like teleconnection. RICE δD is primarily influenced by Amundsen Sea circulation, which coincides with the leading PSA pattern’s (PSA1) circulation focal point in the Amundsen Sea. Additionally, RICE regional physical setting (sheltered from direct impact from Amundsen Sea cyclones by WA orography) offers a unique setting, where enriched isotopes only are associated with one PSA1 polarity (El Niño, PSA1+, Amundsen Sea anticyclones). In contrast, during La Niña and Amundsen Sea cyclones, δD is depleted. Combined these settings, provides a compelling explanation to why RICE δD preserves PSA1 and ENSO variability. On interannual and seasonal time scales, the RICE δD variability is well-explained by the PSA teleconnections and their interactions over the Pacific sector. The influence from PSA2 on δD is strong during the beginning of the year (December–February, DJF). In contrast, the PSA1 influence is strong during the latter part of the year, peaking in spring (September–November, SON). The isotope record appears to preserve tropical Pacific El Niño-like interdecadal variability, particularly a decadal-signal from the central-Pacific (Niño-4 SST region) and from the Pacific-wide Interdecadal Pacific Oscillation (IPO). On decadal-scales RICE δD is modulated by ENSO and Southern Annular Mode (SAM); when the correlation with SAM is active (during IPO+) δD appears to be in a depleted state and when the correlation with SAM breaks down (during IPO−) δD appears to be in a relatively enriched state. A RICE δD SST proxy reconstruction can potentially provide a record longer than the currently available observational datasets, allowing for examination of intrinsic decadal-scale tropical Pacific climate variability and its extratropical impact.</p>

High-Resolution Water Stable Isotope Ice-Core Record: Roosevelt Island, Antarctica

<p>This thesis presents a water-isotope (δD) record from 1900 to 2009 for the Roosevelt Island Climate Evolution (RICE) ice core, Antarctica. Examination of the RICE isotope record with observation data (using global reanalysis and SST datasets) revealed details of the climate signal that is preserved within the full 763 m isotope record. RICE δD provides a proxy record, which captures the central tropical Pacific ENSO variability, the significant (p < 0.01) central Pacific δD-SST correlation pattern contain the Niño-4 SST region. Central tropical Pacific ENSO variability projects upon the Amundsen Sea region via a Pacific–South American pattern (PSA)-like teleconnection. RICE δD is primarily influenced by Amundsen Sea circulation, which coincides with the leading PSA pattern’s (PSA1) circulation focal point in the Amundsen Sea. Additionally, RICE regional physical setting (sheltered from direct impact from Amundsen Sea cyclones by WA orography) offers a unique setting, where enriched isotopes only are associated with one PSA1 polarity (El Niño, PSA1+, Amundsen Sea anticyclones). In contrast, during La Niña and Amundsen Sea cyclones, δD is depleted. Combined these settings, provides a compelling explanation to why RICE δD preserves PSA1 and ENSO variability. On interannual and seasonal time scales, the RICE δD variability is well-explained by the PSA teleconnections and their interactions over the Pacific sector. The influence from PSA2 on δD is strong during the beginning of the year (December–February, DJF). In contrast, the PSA1 influence is strong during the latter part of the year, peaking in spring (September–November, SON). The isotope record appears to preserve tropical Pacific El Niño-like interdecadal variability, particularly a decadal-signal from the central-Pacific (Niño-4 SST region) and from the Pacific-wide Interdecadal Pacific Oscillation (IPO). On decadal-scales RICE δD is modulated by ENSO and Southern Annular Mode (SAM); when the correlation with SAM is active (during IPO+) δD appears to be in a depleted state and when the correlation with SAM breaks down (during IPO−) δD appears to be in a relatively enriched state. A RICE δD SST proxy reconstruction can potentially provide a record longer than the currently available observational datasets, allowing for examination of intrinsic decadal-scale tropical Pacific climate variability and its extratropical impact.</p>

LA-ICP-MS Trace Element Analysis of Planktonic Foraminifera and Application to Marine Isotope Stage 31 in the Southwest Pacific Ocean

<p><b>Trace element/Ca ratios were measured by LA-ICP-MS in Gs. ruber and N. incompta from a wide range of core top and plankton tow samples in the Southwest Pacific Ocean, with particular focus on linking measured Mg/Ca ratios to observed (near-) surface ocean temperatures. Mean Mg/Ca ratios measured in the ultimate chamber F of Gs. ruber are significantly lower compared to chambers F-2 and F-1, which show no statistical difference. These observations led to the development of three new Mg/Ca – ocean temperature calibrations that can be used to reconstruct SST from LA-ICP-MS trace element analysis of Gs. ruber over a temperature range of 14.7-28.8°C. In contrast to the LA-ICP-MS study of Gs. ruber, the planktonic species N. incompta shows no systematic difference in Mg/Ca between the final four visible chambers at one core top site, nor between the F-3 and F chambers at any sites. In addition, there was no correlation between Mg/Ca ratios and ocean temperature in either reticulate or crystalline forms. This may reflect migration of this species within the water column that is not uni-directional, that this species does not dwell at the same depths at each core top site, or point towards further unidentified controls on Mg incorporation into N. incompta that require further study. The chamber specific calibrations developed for Gs. ruber in this study, and a calibration developed using the same techniques for G. bulloides [Marr et al., 2011] were applied down core to Mg/Ca ratios measured from ODP Site 1123. The SST derived from Mg/Ca ratios reveal that during the MIS-31 interglacial, SSTs were approximately 4-5°C warmer than today and 8-9°C warmer than those from MIS-29 and 30. A comparison of SSTs measured from Gs. ruber and G. bulloides, suggests that they are responding to local insolation changes. G. bulloides records colder temperatures than Gs. ruber, which reflects differences in their relative depth in the water column. Paired Mg/Ca and δ 18O data reveal significant changes in ice volume over the sampling period. Increases in SSTs recorded by the planktonic foraminifera lead the seawater stable isotope record by 10 kyr suggesting a significant influence from changes in Northern Hemisphere ice sheet volume during MIS-31. In some intervals, the SST leads the benthic stable isotope record by 8 kyr and shows deviations in benthic δ18O from synchronous planktic samples.</b></p> <p>In G. bulloides and Gs. ruber, Mn and Mg were the only trace elements to show systematic glacial-interglacial changes from MIS-34 to MIS-29. This correlation could imply that Mn/Ca ratios in the foraminifera are recording changes in ocean chemistry related to changing water mass circulation at ODP Site 1123 as past ocean temperatures changed. Size-normalised weights (SNW) of G. bulloides tests show systematic variations from MIS- 34 to MIS-29. For much of the record, SNW is anti-correlated with SST in a manner similar to the modern relationship between SNW and SST in the Southwest Pacific Ocean. However, immediately prior to the MIS-31 Southern Hemisphere insolation maxima, SNW increase with SST suggesting a fundamental change in surface ocean carbonate chemistry occurred that is unique to this time.</p>

LA-ICP-MS Trace Element Analysis of Planktonic Foraminifera and Application to Marine Isotope Stage 31 in the Southwest Pacific Ocean

<p><b>Trace element/Ca ratios were measured by LA-ICP-MS in Gs. ruber and N. incompta from a wide range of core top and plankton tow samples in the Southwest Pacific Ocean, with particular focus on linking measured Mg/Ca ratios to observed (near-) surface ocean temperatures. Mean Mg/Ca ratios measured in the ultimate chamber F of Gs. ruber are significantly lower compared to chambers F-2 and F-1, which show no statistical difference. These observations led to the development of three new Mg/Ca – ocean temperature calibrations that can be used to reconstruct SST from LA-ICP-MS trace element analysis of Gs. ruber over a temperature range of 14.7-28.8°C. In contrast to the LA-ICP-MS study of Gs. ruber, the planktonic species N. incompta shows no systematic difference in Mg/Ca between the final four visible chambers at one core top site, nor between the F-3 and F chambers at any sites. In addition, there was no correlation between Mg/Ca ratios and ocean temperature in either reticulate or crystalline forms. This may reflect migration of this species within the water column that is not uni-directional, that this species does not dwell at the same depths at each core top site, or point towards further unidentified controls on Mg incorporation into N. incompta that require further study. The chamber specific calibrations developed for Gs. ruber in this study, and a calibration developed using the same techniques for G. bulloides [Marr et al., 2011] were applied down core to Mg/Ca ratios measured from ODP Site 1123. The SST derived from Mg/Ca ratios reveal that during the MIS-31 interglacial, SSTs were approximately 4-5°C warmer than today and 8-9°C warmer than those from MIS-29 and 30. A comparison of SSTs measured from Gs. ruber and G. bulloides, suggests that they are responding to local insolation changes. G. bulloides records colder temperatures than Gs. ruber, which reflects differences in their relative depth in the water column. Paired Mg/Ca and δ 18O data reveal significant changes in ice volume over the sampling period. Increases in SSTs recorded by the planktonic foraminifera lead the seawater stable isotope record by 10 kyr suggesting a significant influence from changes in Northern Hemisphere ice sheet volume during MIS-31. In some intervals, the SST leads the benthic stable isotope record by 8 kyr and shows deviations in benthic δ18O from synchronous planktic samples.</b></p> <p>In G. bulloides and Gs. ruber, Mn and Mg were the only trace elements to show systematic glacial-interglacial changes from MIS-34 to MIS-29. This correlation could imply that Mn/Ca ratios in the foraminifera are recording changes in ocean chemistry related to changing water mass circulation at ODP Site 1123 as past ocean temperatures changed. Size-normalised weights (SNW) of G. bulloides tests show systematic variations from MIS- 34 to MIS-29. For much of the record, SNW is anti-correlated with SST in a manner similar to the modern relationship between SNW and SST in the Southwest Pacific Ocean. However, immediately prior to the MIS-31 Southern Hemisphere insolation maxima, SNW increase with SST suggesting a fundamental change in surface ocean carbonate chemistry occurred that is unique to this time.</p>