Stable isotope record, carbonate and organic carbon content of the Miocene section of IODP Site 321-U1337

The Miocene Climatic Optimum (~17-14.7 Ma) represents one of several major interruptions in the long-term cooling trend of the past 50 million years. To date, the processes driving high-amplitude climate variability and sustaining global warmth during this remarkable interval remain highly enigmatic. We present high-resolution benthic foraminiferal and bulk carbonate stable isotope records in an exceptional, continuous, carbonate-rich sedimentary archive (Integrated Ocean Drilling Program Site U1337, eastern equatorial Pacific Ocean), which offer a new view of climate evolution over the onset of the Climatic Optimum. A sharp decline in d18O and d13C at ~16.9 Ma, contemporaneous with a massive increase in carbonate dissolution, demonstrates that abrupt warming was coupled to an intense perturbation of the carbon cycle. The rapid recovery in d13C at ~16.7 Ma, ~200 k.y. after the beginning of the MCO, marks the onset of the first carbon isotope maximum within the long-lasting "Monterey Excursion". These results lend support to the notion that atmospheric pCO2 variations drove profound changes in the global carbon reservoir through the Climatic Optimum, implying a delicate balance between changing CO2 fluxes, rates of silicate weathering and global carbon sequestration. Comparison with a high-resolution d13C record spanning the onset of the Cretaceous Oceanic Anoxic Event 1a (~120 Ma ago) reveals common forcing factors and climatic responses, providing a long-term perspective to understand climate-carbon cycle feedbacks during warmer periods of Earth's climate with markedly different atmospheric CO2 concentrations.

Stable isotopes measured on Miocene benthic foraminifera from ODP sites 202-1237 and 184-1146

One of the most enigmatic features of Cenozoic long-term climate evolution is the long-lasting positive carbon-isotope excursion or "Monterey Excursion", which started during a period of global warmth after 16.9 Ma and ended at not, vert, similar 13.5 Ma, approximately 400 kyr after major expansion of the Antarctic ice-sheet. We present high-resolution (1-9 kyr) astronomically-tuned climate proxy records in two complete sedimentary successions from the northwestern and southeastern Pacific (ODP Sites 1146 and 1237), which shed new light on the middle Miocene carbon-isotope excursion and associated climatic transition over the interval 17.1-12.7 Ma. We recognize three distinct climate phases with different imprints of orbital variations into the climatic signals (1146 and 1237 d18O, d13C; 1237 XRF Fe, fraction > 63 µm): (1) climate optimum prior to 14.7 Ma characterized by minimum ice volume and prominent 100 and 400 kyr variability, (2) long-term cooling from 14.7 to 13.9 Ma, principally driven by obliquity and culminating with rapid cryosphere expansion and global cooling at the onset of the last and most pronounced d13C increase, (3) "Icehouse" mode after 13.9 Ma with distinct 100 kyr variability and improved ventilation of the deep Pacific. The "Monterey" carbon-isotope excursion (16.9-13.5 Ma) consists overall of nine 400 kyr cycles, which show high coherence with the long eccentricity period. Superposed on these low-frequency oscillations are high-frequency variations (100 kyr), which closely track the amplitude modulation of the short eccentricity period. In contrast to d13C, the d18O signal additionally shows significant power in the 41 kyr band, and the 1.2 Myr amplitude modulation of the obliquity cycle is clearly imprinted in the 1146 d18O signal. Our results suggest that eccentricity was a prime pacemaker of middle Miocene climate evolution through the modulation of long-term carbon budgets and that obliquity-paced changes in high-latitude seasonality favored the transition into the "Icehouse" climate.

Results of a sediment profile and water analyses from Lake Hancza in northeastern Poland

We investigated the sedimentary record of Lake Hancza (northeastern Poland) using a multi-proxy approach, focusing on early to mid-Holocene climatic and environmental changes. AMS 14C dating of terrestrial macrofossils and sedimentation rate estimates from occasional varve thickness measurements were used to establish a chronology. The onset of the Holocene at c. 11600 cal. a BP is marked by the decline of Lateglacial shrub vegetation and a shift from clastic-detrital deposition to an autochthonous sedimentation dominated by biochemical calcite precipitation. Between 10000 and 9000 cal. a BP, a further environmental and climatic improvement is indicated by the spread of deciduous forests, an increase in lake organic matter and a 1.7% rise in the oxygen isotope ratios of both endogenic calcite and ostracod valves. Rising d18O values were probably caused by a combination of hydrological and climatic factors. The persistence of relatively cold and dry climate conditions in northeastern Poland during the first one and a half millennia of the Holocene could be related to a regional eastern European atmospheric circulation pattern. Prevailing anticyclonic circulation linked to a high-pressure cell above the retreating Scandinavian Ice Sheet might have blocked the influence of warm and moist Westerlies and attenuated the early Holocene climatic amelioration in the Lake Hancza region until the final decay of the ice sheet.

Stable hydrogen and carbon isotope records and concentration data for four long chain n-alkanes from core GIK16160-3 derived from the Zambezi delta in the Mozambique Channel during the last 37,000 years

Hydrogen isotope values (dD) of sedimentary terrestrial leaf wax such as n-alkanes or n-acids have been used to map and understand past changes in rainfall amount in the tropics because dD of precipitation is commonly assumed as the first order controlling factor of leaf wax dD. Plant functional types and their photosynthetic pathways can also affect leaf wax dD but these biological effects are rarely taken into account in paleo studies relying on this rainfall proxy. To investigate how biological effects may influence dD values we here present a 37,000-year old record of dD and stable carbon isotopes (d13C) measured on four n-alkanes (n-C27, n-C29, n-C31, n-C33) from a marine sediment core collected off the Zambezi River mouth. Our paleo d13C records suggest that each individual n-alkanes had different C3/C4 proportional contributions. n-C29 was mostly derived from a C3 dicots (trees, shrubs and forbs) dominant vegetation throughout the entire record. In contrast, the longer chain n-C33 and n-C31 were mostly contributed by C4 grasses during the Glacial period but shifted to a mixture of C4 grasses and C3 dicots during the Holocene. Strong correlations between dD and d13C values of n-C33 (correlation coefficient R2 = 0.75, n = 58) and n-C31 (R2 = 0.48, n = 58) suggest that their dD values were strongly influenced by changes in the relative contributions of C3/C4 plant types in contrast to n-C29 (R2 = 0.07, n = 58). Within regions with variable C3/C4 input, we conclude that dD values of n-C29 are the most reliable and unbiased indicator for past changes in rainfall, and that dD and d13C values of n-C31 and n-C33 are sensitive to C3/C4 vegetation changes. Our results demonstrate that a robust interpretation of palaeohydrological data using n-alkane dD requires additional knowledge of regional vegetation changes from which nalkanes are synthesized, and that the combination of dD and d13C values of multiple n-alkanes can help to differentiate biological effects from those related to the hydrological cycle.

(Table T1) In situ methane concentrations of ODP Site 201-1230

A method for quantifying in situ dissolved methane concentrations in sediment cores that have gas voids is described. The method relies on normalizing methane (CH4) in the gas voids to nitrogen (N2) and/or argon (Ar). The principles of the method are presented. The method was tested during Ocean Drilling Program Leg 201, and preliminary results indicate that it can be used to generate reproducible and accurate dissolved methane values if argon and nitrogen are both measured or if one is measured along with pressure of the gas void.

Disposal of an integrated pulp-paper mill effluent by irrigation /

Mode of access: Internet.

Subject headings for the aeronautical index /

Mimeographed.

Fire sange : op. 28 /

Mode of access: Internet.

Proceedings : first International Conference on Numerical Ship Hydrodynamics, 20-22 Oct. 1975 /

"Dedicated to the memory of Reinier Timman (1917-1975)."

Studia Lucanea ... scripsit ...

Errata slip inserted at end.

Plant-breeding; comments on the experiments of Nilsson and Burbank,

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Observations faites au Cap Thordsen, Spitzberg /

Each part also has special title page

Trattato delle malattie de'bambini /

Mode of access: Internet.