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There is a temporal correlation between the peak activity of the North Atlantic Igneous Province (NAIP) and the Paleocene–Eocene Thermal Maximum (PETM), suggesting that the NAIP may have initiated and/or prolonged this extreme warming event. However, corroborating a causal relationship is hampered by a scarcity of expanded sedimentary records that contain both climatic and volcanic proxies. One locality hosting such a record is the island of Fur in Denmark, where an expanded pre- to post-PETM succession containing hundreds of NAIP ash layers is exceptionally well preserved. We compiled a range of environmental proxies, including mercury (Hg) anomalies, paleotemperature proxies, and lithium (Li) and osmium (Os) isotopes, to trace NAIP activity, hydrological changes, weathering, and seawater connectivity across this interval. Volcanic proxies suggest that NAIP activity was elevated before the PETM and appears to have peaked during the body of the δ13 C excursion but decreased considerably during the PETM recovery. This suggests that the acme in NAIP activity, dominated by flood basalt volcanism and thermogenic degassing from contact metamorphism, was likely confined to just ∼ 200 kyr (ca. 56.0–55.8 Ma). The hundreds of thick (> 1 cm) basaltic ashes in the post-PETM strata likely represent a change from effusive to explosive activity, rather than an increase in NAIP activity. Detrital δ7 Li values and clay abundances suggest that volcanic ash production increased the basaltic reactive surface area, likely enhancing silicate weathering and atmospheric carbon sequestration in the early Eocene. Signals in lipid biomarkers and Os isotopes, traditionally used to trace paleotemperature and weathering changes, are used here to track seaway connectivity. These proxies indicate that the North Sea was rapidly cut off from the North Atlantic in under 12 kyr during the PETM recovery due to NAIP thermal uplift. Our findings reinforce the hypothesis that the emplacement of the NAIP had a profound and complex impact on Paleocene–Eocene climate, both directly through volcanic and thermogenic degassing and indirectly by driving regional uplift and changing seaway connectivity. [ABSTRACT FROM AUTHOR]

There is a temporal correlation between the peak activity of the North Atlantic Igneous Province (NAIP) and the Paleocene–Eocene Thermal Maximum (PETM), suggesting that the NAIP may have initiated and/or prolonged this extreme warming event. However, corroborating a causal relationship is hampered by a scarcity of expanded sedimentary records that contain both climatic and volcanic proxies. One locality hosting such a record is Fur Island in Denmark, where an expanded pre- to post-PETM succession containing hundreds of NAIP ash layers is exceptionally well preserved. We compiled a range of environmental proxies, including mercury (Hg) anomalies, paleotemperature proxies, and lithium (Li) and osmium (Os) isotopes, to trace NAIP activity, hydrological changes, weathering, and seawater connectivity across this interval. Volcanic proxies suggest that NAIP activity was elevated before the PETM and appears to have peaked during the body of the δ13C excursion, but decreased considerably during the PETM recovery. This suggests that the acme in NAIP activity, dominated by flood basalt volcanism and thermogenic degassing from contact metamorphism, was likely confined to just ~200 kyr (ca. 56.0–55.8 Ma). The hundreds of thick basaltic ashes in the post-PETM strata likely represent a change from effusive to explosive activity, rather than an increase in NAIP activity. Detrital δ7Li values and clay abundances suggest that volcanic ash production increased basaltic reactive surface area, likely enhancing silicate weathering and atmospheric carbon sequestration in the early Eocene. Signals in lipid biomarkers and Os isotopes, traditionally used to trace paleotemperature and weathering changes, are used here to track seaway connectivity. These proxies indicate that the North Sea was rapidly cut off from the North Atlantic in under 12 kyr during the PETM recovery due to NAIP thermal uplift. Our findings reinforce the hypothesis that the emplacement of the NAIP had a profound and complex impact on Paleocene–Eocene climate, both directly through volcanic and thermogenic degassing, and indirectly by driving regional uplift and changing seaway connectivity. [ABSTRACT FROM AUTHOR]

The Campanian age (Late Cretaceous) is characterized by a warm greenhouse climate with limited land-ice volume. This makes this period an ideal target for studying climate dynamics during greenhouse periods, which are essential for predictions of future climate change due to anthropogenic greenhouse gas emissions. Well-preserved fossil shells from the Campanian (±78 Ma) high mid-latitude (50 ∘ N) coastal faunas of the Kristianstad Basin (southern Sweden) offer a unique snapshot of short-term climate and environmental variability, which complements existing long-term climate reconstructions. In this study, we apply a combination of high-resolution spatially resolved trace element analyses (micro-X-ray fluorescence – µ XRF – and laser ablation inductively coupled plasma mass spectrometry – LA-ICP-MS), stable isotope analyses (IRMS) and growth modeling to study short-term (seasonal) variations recorded in the oyster species Rastellum diluvianum from the Ivö Klack locality. Geochemical records through 12 specimens shed light on the influence of specimen-specific and ontogenetic effects on the expression of seasonal variations in shell chemistry and allow disentangling vital effects from environmental influences in an effort to refine paleoseasonality reconstructions of Late Cretaceous greenhouse climates. Growth models based on stable oxygen isotope records yield information on the mode of life, circadian rhythm and reproductive cycle of these extinct oysters. This multi-proxy study reveals that mean annual temperatures in the Campanian higher mid-latitudes were 17 to 19 ∘ C, with winter minima of ∼13 ∘ C and summer maxima of 26 ∘ C, assuming a Late Cretaceous seawater oxygen isotope composition of - 1 ‰ VSMOW (Vienna standard mean ocean water). These results yield smaller latitudinal differences in temperature seasonality in the Campanian compared to today. Latitudinal temperature gradients were similar to the present, contrasting with previous notions of "equable climate" during the Late Cretaceous. Our results also demonstrate that species-specific differences and uncertainties in the composition of Late Cretaceous seawater prevent trace element proxies (Mg/Ca , Sr/Ca , Mg/Li and Sr/Li) from being used as reliable temperature proxies for fossil oyster shells. However, trace element profiles can serve as a quick tool for diagenesis screening and investigating seasonal growth patterns in ancient shells. [ABSTRACT FROM AUTHOR]

The mass loss from the Greenland Ice Sheet has increased over the past 2 decades. Marine-terminating glaciers contribute significantly to this mass loss due to increased melting and ice discharge. Periods of rapid retreat of these tidewater glaciers have been linked to the concurrent inflow of warm Atlantic-sourced waters. However, little is known about the variability of these Atlantic-derived waters within the fjords, due to a lack of multi-annual in situ measurements. Thus, to better understand the potential role of ocean warming on glacier retreat, reconstructions that characterize the variability of Atlantic water inflow to the fjords are required. Here, we investigate foraminiferal assemblages in a sediment core from Upernavik Fjord, West Greenland, in which the major ice stream Upernavik Isstrøm terminates. We conclude that the foraminiferal assemblage is predominantly controlled by changes in bottom water composition and provide a reconstruction of Atlantic water inflow to Upernavik Fjord, spanning the period 1925–2012. This reconstruction reveals peak Atlantic water influx during the 1930s and again after 2000, a pattern that is comparable to the Atlantic Multidecadal Oscillation (AMO). The comparison of these results to historical observations of front positions of Upernavik Isstrøm reveals that inflow of warm Atlantic-derived waters likely contributed to high retreat rates in the 1930s and after 2000. However, moderate retreat rates of Upernavik Isstrøm also prevailed in the 1960s and 1970s, showing that glacier retreat continued despite a reduced Atlantic water inflow, albeit at a lower rate. Considering the link between bottom water variability and the AMO in Upernavik Fjord, and the fact that a persistent negative phase of the AMO is expected for the next decade, Atlantic water inflow into the fjord may decrease in the coming decade, potentially minimizing or stabilizing the retreat of Upernavik Isstrøm during this time interval. [ABSTRACT FROM AUTHOR]

The mass loss from the Greenland Ice Sheet has increased over the past two decades. Marine-terminating glaciers contribute significantly to this mass loss due to increased melting and ice discharge. Rapid retreat periods of these tidewater glaciers have been linked to the concurrent inflow of warm, Atlantic derived waters. However, little is known about the variability of Atlantic-derived waters within these fjords, due to a lack of multi-annual, in situ measurements. Thus, to better understand the potential role of ocean warming on glacier retreat, reconstructions that characterize the variability of Atlantic water inflow to these fjords are required. Here, we investigate foraminiferal assemblages in a sediment core from Upernavik Fjord, West Greenland, in which the major ice stream Upernavik Isstr⊘m terminates. We investigate the environmental characteristics that control species diversity and derive that it is predominantly controlled by changes in bottom water variability. Hence, we provide a reconstruction of Atlantic water inflow to Upernavik Fjord, spanning the period 1925-2012. This reconstruction reveals peak Atlantic water inflow during the 1930s and again after 2000, a pattern that is similar to the Atlantic Multidecadal Oscillation (AMO). We compare these results to historical observations of front positions of Upernavik Isstr⊘m. This reveals that inflow of warm, Atlantic-derived waters indeed likely contributed to high retreat rates in the 1930s and after 2000. However, moderate retreat rates of Upernavik Isstr⊘m also prevailed in the 1960s/1970s, showing that retreat continued despite reduced Atlantic water inflow, albeit at a lower rate. Considering the link between bottom water variability and the AMO in Upernavik Fjord and the fact that a persistent negative phase of the AMO is expected for the next decade, Atlantic water inflow into the fjord may decrease in the next ~ 10 years. [ABSTRACT FROM AUTHOR]

The late Campanian – Maastrichtian (~74–66 Ma) was characterized by a long-term cooling trend that marks a transition from extreme greenhouse conditions associated with the mid-Cretaceous to cooler conditions that precede the Cenozoic climate. Sparse availability of stable isotope data and the low temporal resolution of biozonations hinder our understanding of this interval, especially for open ocean records. Provincialism of calcareous planktonic taxa also occurred during this time, making it difficult to develop a global biostratigraphic scheme. Calcareous nannofossils are sensitive indicators of surface water, making this fossil group a useful proxy for understanding Late Cretaceous climatic events and correlating these events across different ocean basins. This study expands on the work of Thibault and Gardin (2007), that explored the paleoclimatic evolution of late Maastrichtian calcareous nannofossils from Deep Sea Drilling Project (DSDP) Hole 525A in the South Atlantic. The completeness of its late Campanian – Maastrichtian record makes Hole 525A an ideal site for this study. Furthermore, high-resolution stable isotope datasets have been published, making this section useful for correlation to other ocean basins. A total of 72 smear slides from DSDP Hole 525A, spanning approximately 74–66 Ma, were analyzed. Absolute abundances were determined by counting approximately 300 specimens and two additional traverses were scanned for rare species. Given that this is a low middle latitude site, the calcareous nannofossil assemblage is predominantly comprised of cosmopolitan species, with little evidence of provincialism. This means that sea surface temperature changes are not as well expressed at this site. Despite the dominance of cosmopolitan species, abundance increases of "Cool-water indicators" (Ahmuellerella octoradiata, Kamptnerius magnificus and Nephrolithus frequens) are still observed in this section.In addition to the evidence presented for cool surface water conditions prevailing during the late Maastrichtian (Chron C30N) (Thibault and Gardin, 2007), increases in "Cool-water indicators" are also observed at the base of the early Maastrichtian (Chron C32n1r through the middle of Chron C31r) and two peaks during the late early Maastrichtian (uppermost Chron C31r). These fluxes of "Cool-water indicators" further support onset of global cooling during the late Campanian – early Maastrichtian, evidenced by a rapid, positive oxygen benthic foraminiferal isotope excursion recorded at numerous deep ocean sites. Traditionally viewed as a low-fertility indicator, the gradual decrease in abundance of Watznaueria barnesiae is observed throughout the section, seemingly following the gradual global cooling trend. Fluctuations in abundance are superimposed on this general decrease. The highest abundances precede the Campanian/Maastrichtian boundary. Increases in abundance also occur throughout the middle Maastrichtian (Chron 31n through Chron 30r), possibly coinciding with the collapse of rudist bivalve-dominated reef systems and the extinction of inoceramid bivalves during the Mid-Maastrichtian event. ReferencesThibault, N., & Gardin, S. (2007). The late Maastrichtian nannofossil record of climate change in the South Atlantic DSDP Hole 525A. Marine Micropaleontology, 65(3), 163-184. [ABSTRACT FROM AUTHOR]

The Middle Ordovician outer shelf section of Steinsodden (Norway) shows exquisite marl-limestone alternations with subtle variations in thickness. The section is very well-dated by conodonts allowing correlation to the Baltoscandian conodont and graptolite zonations, and spans the Dapingian to Darriwilian stages. Here, we demonstrate an unambiguous orbital origin of the alternations, allowing for an astronomical calibration of this important time interval that spans the main radiation phase of the Great Ordovician Biodiversification Event (GOBE). A shift in carbonate sedimentation from precession-dominated in the Dapingian and lower Darriwilian to 405 kyr eccentricity-dominated in the middle Darriwilian is in direct coincidence with an increase in the diversity of Baltoscandian conodonts. The conodont diversification correlates with a similar increase in the diversity of Baltoscandian brachiopods, which in turn, have been shown to coincide with a +1‰ increase in benthic oxygen isotopes. The amplitude of isotopic change and its coincidence to the major switch in the dominance of orbital components reflect a scenario that bears similarities to that of the Eocene/Oligocene boundary transition, suggesting that glaciation could have triggered the main radiation phase of the GOBE. [ABSTRACT FROM AUTHOR]

Drilled in 1983, DSDP Site 534A is a prime location to investigate marl-limestone alterations from the middle Tithonian to the earliest Barremian. In 336 metres, the studied interval encompasses a nearly complete succession, allowing a high-resolution long-term study for this critical interval of Earth's history. To strengthen the Stratigraphy of the Jurassic-Cretaceous system boundary, we integrate the already published magnetostratigraphic, chemostratigraphic (bulk carbonate carbon isotopes) and biostratigraphic framework of the core (based on nannofossils, radiolarians, dinoflagellates and calpionellids) with cyclostratigraphy based on high-resolution (4cm) XRF data. Astronomical tuning of the core suggests a total duration of ~19 million years for the studied interval. Interestingly, long-term trends in the Ca/Fe ratio compare well with that of carbon isotopes. These trends are forced by the 9.1 Myr grand eccentricity cycle, placing the Weissert event close to a maximum of this grand cycle. Astronomical configuration appears to have played a major role in the development of this oceanic anoxic event. [ABSTRACT FROM AUTHOR]

In the Northern Calcareous Alps of Austria, Tethyan marls, clays and limestones of the upper Zlambach facies outcrop in excellent conditions in the Roßmoosgraben section (east of Bad Goisern, Oberösterreich). These sediments were deposited in a toe-of-slope to basinal paleoenvironment and thus constitute a rare example of Rhaetian open ocean conditions of the northern Tethys. Calcareous nannofossils are abundant in these sediments and their preservation is generally moderate, allowing for assessing potential changes in assemblages. Absolute and relative abundances of nannofossils and changes in the size of Prinsiosphaera triassica have been established for 65 samples across the V. stuerzenbaumi to C. marshi ammonite zones and compared to high-resolution bulk carbonate carbon isotopes. Two large 1.5 per mil negative excursions in carbon isotopes are recorded in the C. marshi zone and are accompanied by significantly lower total abundance in calcareous nannofossils but no significant change in the composition of the assemblage. Organic-rich black shales prevail in the uppermost 3 m of the Roßmoosgraben section and contain an unusually high abundance of the nannolith Tetralithus and significantly smaller specimens of Prinsiosphaera triassica. In addition, the total number of coccoliths, which represent the earliest representatives of coccolithophorids, is higher in this interval. These results suggest that a possible change in fertility conditions of surface waters favoured the thriving of the primitive coccolithophorids and accompanied bottom water anoxia. Our study shows that even though Rhaetian calcareous nannofossil assemblages have a low diversity, changes in their composition and in their size can be used to depict significant environmental changes. Also, the Rhaetian was characterized by unstable environmental conditions as attested by rapid shifts in the carbon cycle and episodes of ocean anoxia. [ABSTRACT FROM AUTHOR]