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The climate and environmental significance of the Deccan Traps large igneous province of west-central India has been the subject of debate in paleontological communities. Nearly one million years of semi-continuous Deccan eruptive activity spanned the Cretaceous-Paleogene boundary, which is renowned for the extinction of most dinosaur groups. Whereas the Chicxulub impactor is acknowledged as the principal cause of these extinctions, the Deccan Traps eruptions are believed to have contributed to extinction patterns and/or enhanced ecological pressures on biota during this interval of geologic time. We present the first coupled records of biogenic carbonate clumped isotope paleothermometry and mercury concentrations as measured from a broad geographic distribution of marine mollusk fossils. These fossils preserve evidence of simultaneous increases in coastal marine temperatures and mercury concentrations at a global scale, which appear attributable to volcanic CO2 and mercury emissions. These early findings warrant further investigation with additional records of combined Late Cretaceous temperatures and mercury concentrations of biogenic carbonate., The relative role of the Deccan Traps volcanic activity versus the role of the Chicxulub impact event in terms of potential contributions to the Cretaceous-Paleogene (K-Pg) mass extinction has been subject to longstanding debate. Here, the authors observe a global signal of abruptly increased ocean temperatures and elevated [Hg] in the same biogenic carbonate specimens, prior to the impact event but aligning with the onset of Deccan volcanism.

The cause of the end-Cretaceous (KPg) mass extinction is still debated due to difficulty separating the influences of two closely timed potential causal events: eruption of the Deccan Traps volcanic province and impact of the Chicxulub meteorite. Here we combine published extinction patterns with a new clumped isotope temperature record from a hiatus-free, expanded KPg boundary section from Seymour Island, Antarctica. We document a 7.8±3.3 °C warming synchronous with the onset of Deccan Traps volcanism and a second, smaller warming at the time of meteorite impact. Local warming may have been amplified due to simultaneous disappearance of continental or sea ice. Intra-shell variability indicates a possible reduction in seasonality after Deccan eruptions began, continuing through the meteorite event. Species extinction at Seymour Island occurred in two pulses that coincide with the two observed warming events, directly linking the end-Cretaceous extinction at this site to both volcanic and meteorite events via climate change., The cause of the end-Cretaceous mass extinction is still debated due to difficulties separating the influences of two closely-timed potential causal events (massive volcanism and meteorite impact). Here, the authors link the extinction to both kill mechanisms through a new paleotemperature record.

The Palaeocene–Eocene thermal maximum (PETM) is a well-known abrupt warming that occurred about 55.8 million years ago and is usually thought to have been caused by a large release of greenhouse gases, probably from methane hydrates, as recorded in a large carbon isotope excursion. Ross Secord and colleagues have used isotopic analysis of mammal teeth from the Bighorn Basin, Wyoming, to show that continental warming of about 5 °C preceded the isotopic excursion. The PETM therefore seems to have been caused by at least two separate warming events, each forced by different processes. The Palaeocene–Eocene thermal maximum (PETM) is a well-known abrupt warming that occurred at about 55.8 Myr ago and is usually thought to have been caused by a large release of greenhouse gases, as recorded in a large carbon isotope excursion. Yet some marine evidence suggests that in fact the warming came first. Here it is shown that continental warming of about 5 °C preceded the excursion in the Bighorn Basin, Wyoming. Thus the PETM seems to have been caused by at least two separate warming events. Marine and continental records1 show an abrupt negative shift in carbon isotope values at ∼55.8 Myr ago. This carbon isotope excursion (CIE) is consistent with the release of a massive amount of isotopically light carbon into the atmosphere and was associated with a dramatic rise in global temperatures termed the Palaeocene–Eocene thermal maximum (PETM). Greenhouse gases released during the CIE, probably including methane, have often been considered the main cause of PETM warming. However, some evidence from the marine record suggests that warming directly preceded the CIE2,3,4, raising the possibility that the CIE and PETM may have been linked to earlier warming with different origins. Yet pre-CIE warming is still uncertain. Disentangling the sequence of events before and during the CIE and PETM is important for understanding the causes of, and Earth system responses to, abrupt climate change. Here we show that continental warming of about 5 °C preceded the CIE in the Bighorn Basin, Wyoming. Our evidence, based on oxygen isotopes in mammal teeth (which reflect temperature-sensitive fractionation processes) and other proxies, reveals a marked temperature increase directly below the CIE, and again in the CIE. Pre-CIE warming is also supported by a negative amplification of δ13C values in soil carbonates below the CIE. Our results suggest that at least two sources of warming—the earlier of which is unlikely to have been methane—contributed to the PETM.

This study addressed the efficacy and toxicity of the novel compound Bryostatin-1 (NSC 339555), a novel agent with antineoplastic, hematopoietic and immunomodulatory activity in a variety of in vitro and in vivo systems.This phase II study randomly assigned chemotherapy-naïve patients with untreated metastatic melanoma and measurable disease to two schedules of treatment: Arm A, 25 microg/m2 bryostatin-1 given as a 24 hour continuous infusion weekly or Arm B, 120 microg/m2 bryostatin-1 given as a 72 hour continuous infusion every 2 weeks. Although objective response was assessed using standard NCIC CTG criteria, antitumour activity was assessed using a multivariate endpoint incorporating both response (CR and PR) and early progression (PD ator = 8 weeks). Seventeen patients were randomized to each arm.Arm A was better tolerated with 86.7% of 15 evaluable patients receivingor = 90% of planned dose intensity versus 76.5% of 17 evaluable patients in Arm B. On Arm B, three patients experienced serious adverse events and three patients had to be removed from protocol therapy due to toxicity. The most common side effect was myalgia (33% grade 1-2 on Arm A versus 65% on Arm B with 5 patients experiencing grade 3 and one patient grade 4). Lethargy was more common on Arm A but more severe on Arm B. Other side effects such as nausea, diarrhea and headache were generally mild to moderate in nature and occurred with a similar frequency on both arms. Hematologic and biochemical toxicity were minimal. This trial was closed early because the protocol-stopping rule was met based on lack of required responses and on the number of early progressions on both arms. No partial or complete responses were seen; 3 patients randomized to Arm A had stable disease (duration 9-24 weeks) as did 4 patients (duration 10-38 weeks) randomized to Arm B.Arm A was better tolerated than Arm B. We conclude that bryostatin-1 has little efficacy in the treatment of metastatic melanoma with either of the schedules studied.

Three estuaries near Naples, Florida with variably modified watersheds have been investigated to understand the chemical consequences of altering drainage patterns. Blackwater River (near natural drainage, control site), Henderson Creek (moderately modified watershed), and Faka-Union Canal (severe channelization) were sampled for temperature, salinity, δ18O, δ13C of dissolved inorganic carbon (DIC), molality of CO2 (ΣCO2), and Mg:Ca and Sr:Ca ratios between freshwater and marine water end members over a 17-mo period. Carbon isotope composition followed similar seasonal patterns as salinity. Freshwater and seawater end members are more negative than the global average, likely reflecting equilibration with local carbon sources derived from mangrove leaf litter and groundwater. δ13C responds to differences in primary productivity between estuaries. Henderson Creek has higher primary productivity than Blackwater River (probable due to higher sewage input and agricultural runoff) and has more positive δ13C and lower ΣCO2. δ18O is affected by seasonal input of freshwater from atmospheric precipitation, evaporation, and groundwater. Late summer and fall rains lower the δ18O of estuarine water, whereas evaporative conditions in the dry season elevate δ18O to values that can be more positive upstream than those from the Gulf of Mexico (estuarine inversion). Evaporation produces water in the Gulf of Mexico that is >1‰ more positive than the global sea surface average most of the year. The very negative δ18O values in Blackwater River and Henderson Creek likely reflect atmospheric and groundwater contribution. Mg:Ca and Sr:Ca ratios of Gulf water from all three estuaries are similar to global averages at low latitudes. Freshwater end members among estuaries are different in that Blackwater River has higher ratios, suggesting a groundwater contribution. Dolomitic rocks in the subsurface likely provide a source of Mg ions.

The Eocene/Oligocene boundary, at about 33.7 Myr ago, marks one of the largest extinctions of marine invertebrates in the Cenozoic period. For example, turnover of mollusc species in the US Gulf coastal plain was over 90% at this time. A temperature change across this boundary--from warm Eocene climates to cooler conditions in the Oligocene--has been suggested as a cause of this extinction event, but climate reconstructions have not provided support for this hypothesis. Here we report stable oxygen isotope measurements of aragonite in fish otoliths--ear stones--collected across the Eocene/Oligocene boundary. Palaeo-temperatures reconstructed from mean otolith oxygen isotope values show little change through this interval, in agreement with previous studies. From incremental microsampling of otoliths, however, we can resolve the seasonal variation in temperature, recorded as the otoliths continue to accrete new material over the life of the fish. These seasonal data suggest that winters became about 4 degrees C colder across the Eocene/Oligocene boundary. We suggest that temperature variability, rather than change in mean annual temperature, helped to cause faunal turnover during this transition.

The stable isotopic records of ostracode valves deposited during the last interglaciation in Raymond Basin, Illinois, have δ13C and δ18O values as high as +16.5‰ and +9.2‰ respectively, the highest values yet reported from continental ostracodal calcite. Located in south-central Illinois, Raymond, Pittsburg, Bald Knob, and Hopwood Farm basins collectively have yielded important long pollen and ostracode records that date from about 130 000 years ago to the present. Although fossils from the present-day interglaciation are not well preserved, these records constitute the only described, conformable, fossiliferous successions of this age from the interior of glaciated North America.

Textural and compositional attributes of dolomite and calcite within Lower Cretaceous Peterson Limestone micrite indicate that these phases coprecipitated during stabilization of precursor magnesian calcite in a largely closed diagenetic system. Uniform difference in the isotopic compositions of contained carbonate phases over a range of whole rock compositions reflect equilibrium partitioning of18O and13C between dolomite and calcite. Diagenetic dolomite is enriched in18O by 4.4 o/oo and in13C by 1.8 o/oo relative to co-existing calcite, values which are discemibly different from expected open system mixing trends, and which are in general agreement with high temperature fractionation data extrapolated to sedimentary temperatures as well as with calculated δ18O dolomite-calcite from Holocene dolomites.

The oxygen isotopic compositions of tests of Foraminifera are quantitatively related to global ice volume1,2 and local temperature and salinity conditions in which the Foraminifera grew3–8. Thus, a well-preserved sample of deep-sea core contains information about sea-surface temperature (shallow-dwelling planktonic Foraminifera), structure of the thermocline (deeper-dwelling planktonic Foraminifera), and bottom water temperature (benthic Foraminifera), and the global ice volume effect is also superimposed. The progress which has been made in calibration of core–top isotopic data to modern oceanographic data5,7,8, has led us to test state-of-the-art core–top methodology and calibration on a late Miocene time slice (6.0 ± 0.5 Myr BP) of the Atlantic Ocean. Samples studied can be related to either uppermost Zone NN11 or lowermost NN12 of Martini9 and uppermost Zone N17 of Blow10.