Dissolved organic matter (DOM) is omnipresent in natural waters and is commonly incorporated into carbonates. Records of DOM from speleothems (secondary carbonates found in caves) have often been interpreted to reflect groundwater DOM concentrations.However, the fidelity of these records is largely untested. An understanding of the relationship between dripwater and speleothem DOM is thus required to allow speleothems to be reliably used as archives of DOM concentration.We precipitated calcite (CaCO3) crystals from weak solutions of (NH4)2CO3, CaCl2 and NH4Cl. These solutions also contained peat DOM (from 0 to 15 mgC/Lppm). Fluorescence 3D excitation-emission matrix (3D EEM) analysis showed a strong, positive correlation between [DOM] in the parent-solutionaq, and [DOM]calcite in the calcite. Calcite precipitation was reduced at high DOM concentrations, potentially indicating inhibition of crystallisation. Partition coefficient values showed that DOMaq was subtly preferentially incorporated into calcite. Scanning electron microscope images indicated that the crystal structures were heavily influenced by DOM adsorption with finer, smooth-faced, rhombohedral crystals forming in growth solutions with low aqueous [DOM]aq (0-5 mgC/Lppm), and prismatic, 'impure' crystals produced at high aqueous [DOM]aq (10 and 15 mgC/Lppm). Overall, our results indicate that authigenic carbonates are likely to faithfully record variations in aqueous [DOM]aq within the natural range of DOM concentrations in representative freshwater systems (caves, soil water), and that crystal habits are altered by aqueous [DOM]aq within their growth solutions.We also applied our findings to three flowstones collected from three New Zealand caves which vary in climatic, vegetation and hydrological regimes. We conclude that differences in initial aqueous [DOM]aq do indeed control incorporation of DOM into calcite, and thus 3D EEM fluorescence can be used to reconstruct original aqueous [DOM]aq from authigenic carbonates.

A rise in atmospheric CO 2 is believed to be necessary for the termination of large-scale glaciations. Although the Antarctic Ice Sheet is estimated to have melted from ~125% to ~50% its modern size, there is thus far no evidence for an increase in atmospheric CO 2 associated with the Mi-1 glacial termination in the earliest Miocene. Here, we present evidence from a highresolution terrestrial record of leaf physiological change in southern New Zealand for an abrupt increase in atmospheric CO 2 coincident with the termination of the Mi-1 glaciation and lasting approximately 20 kyr. Quantitative pCO 2 estimates, made using a leaf gas exchange model, suggest that atmospheric CO 2 levels may have doubled during this period, from 516 ± 111 ppm to 1144 ± 410 ppm, and subsequently returned back to 425 ± 53 ppm. The 20-kyr interval with high pCO 2 estimates is also associated with a period of increased moisture supply to southern New Zealand, inferred from carbon and hydrogen isotopes of terrestrial leaf waxes. The results provide the first high-resolution record of terrestrial environmental change at the Oligocene/Miocene boundary, document a ~20 kyr interval of elevated pCO 2 and increased local

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Abstract. Cave microclimate and geochemical monitoring is vitally important for correct interpretations of proxy time series from speleothems with regard to past climatic and environmental dynamics. We present results of a comprehensive cave-monitoring programme in Waipuna Cave in the North Island of New Zealand, a region that is strongly influenced by the Southern Westerlies and the El Niño–Southern Oscillation (ENSO). This study aims to characterise the response of the Waipuna Cave hydrological system to atmospheric circulation dynamics in the southwestern Pacific region in order to assure the quality of ongoing palaeo-environmental reconstructions from this cave. Drip water from 10 drip sites was collected at roughly monthly intervals for a period of ca. 3 years for isotopic (δ18O, δD, d-excess parameter, δ17O, and 17Oexcess) and elemental (Mg∕Ca and Sr∕Ca) analysis. The monitoring included spot measurements of drip rates and cave air CO2 concentration. Cave air temperature and drip rates were also continuously recorded by automatic loggers. These datasets were compared to surface air temperature, rainfall, and potential evaporation from nearby meteorological stations to test the degree of signal transfer and expression of surface environmental conditions in Waipuna Cave hydrochemistry. Based on the drip response dynamics to rainfall and other characteristics, we identified three types of discharge associated with hydrological routing in Waipuna Cave: (i) type 1 – diffuse flow, (ii) type 2 – fracture flow, and (iii) type 3 – combined flow. Drip water isotopes do not reflect seasonal variability but show higher values during severe drought. Drip water δ18O values are characterised by small variability and reflect the mean isotopic signature of precipitation, testifying to rapid and thorough homogenisation in the epikarst. Mg∕Ca and Sr∕Ca ratios in drip waters are predominantly controlled by prior calcite precipitation (PCP). Prior calcite precipitation is strongest during austral summer (December–February), reflecting drier conditions and a lack of effective infiltration, and is weakest during the wet austral winter (July–September). The Sr∕Ca ratio is particularly sensitive to ENSO conditions due to the interplay of congruent or incongruent host rock dissolution, which manifests itself in lower Sr∕Ca in above-average warmer and wetter (La Niña-like) conditions. Our microclimatic observations at Waipuna Cave provide a valuable baseline for the rigorous interpretation of speleothem proxy records aiming at reconstructing the past expression of Pacific climate modes.