Shallow-level sill emplacement can uplift Earth's surface via forced folding, providing insight into the location and size of potential volcanic eruptions. Linking the structure and dynamics of ground deformation to sill intrusion is thus critical in volcanic hazard assessment. This is challenging, however, because (1) active intrusions cannot be directly observed, meaning that we rely on transient host-rock deformation patterns to model their structure; and (2) where ancient sill-fold structure can be observed, magmatism and deformation has long since ceased. To address this problem, we combine structural and dynamic analyses of the Alu dome, Ethiopia, a 3.5-km-long, 346-m-high, elliptical dome of outward-dipping, tilted lava flows cross-cut by a series of normal faults. Vents distributed around Alu feed lava flows of different ages that radiate out from or deflect around its periphery. These observations, coupled with the absence of bounding faults or a central vent, imply that Alu is not a horst or a volcano, as previously thought, but is instead a forced fold. Interferometric synthetic aperture radar data captured a dynamic growth phase of Alu during a nearby eruption in A.D. 2008, with periods of uplift and subsidence previously attributed to intrusion of a tabular sill at 1 km depth. To localize volcanism beyond its periphery, we contend that Alu is the first forced fold to be recognized to be developing above an incrementally emplaced saucershaped sill, as opposed to a tabular sill or laccolith.

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Large Igneous Provinces (LIPs) are associated with the largest climate perturbations in Earth’s history. The North Atlantic Igneous Province (NAIP) and Paleocene-Eocene Thermal Maximum (PETM) constitute an exemplar of this association. As yet we have no means to reconstruct the pacing of LIP greenhouse gas emissions for comparison with climate records at millennial resolution. Here, we calculate carbon-based greenhouse gas fluxes associated with the NAIP at sub-millennial resolution by linking measurements of the mantle convection process that generated NAIP magma with observations of the individual geological structures that controlled gas emissions in a Monte Carlo framework. These simulations predict peak emissions flux of 0.2–0.5 PgC yr–1 and show that the NAIP could have initiated PETM climate change. This is the first predictive model of carbon emissions flux from any proposed PETM carbon source that is directly constrained by observations of the geological structures that controlled the emissions.

The response of the Earth system to greenhousegas-driven warming is of critical importance for the future trajectory of our planetary environment. Hyperthermal events -past climate transients with global-scale warming significantly above background climate variability -can provide insights into the nature and magnitude of these responses. The largest hyperthermal of the Cenozoic was the Paleocene-Eocene Thermal Maximum (PETM ∼ 56 Ma). Here we present new high-resolution bulk sediment stable isotope and major element data for the classic PETM section at Zumaia, Spain. With these data we provide a new detailed stratigraphic correlation to other key deep-ocean and terrestrial PETM reference sections. With this new correlation and age model we are able to demonstrate that detrital sediment accumulation rates within the Zumaia continental margin section increased more than 4-fold during the PETM, representing a radical change in regional hydrology that drove dramatic increases in terrestrial-to-marine sediment flux. Most remarkable is that detrital accumulation rates remain high throughout the body of the PETM, and even reach peak val-ues during the recovery phase of the characteristic PETM carbon isotope excursion (CIE). Using a series of Earth system model inversions, driven by the new Zumaia carbon isotope record, we demonstrate that the silicate weathering feedback alone is insufficient to recover the PETM CIE, and that active organic carbon burial is required to match the observed dynamics of the CIE. Further, we demonstrate that the period of maximum organic carbon sequestration coincides with the peak in detrital accumulation rates observed at Zumaia. Based on these results, we hypothesise that orbitalscale variations in subtropical hydro-climates, and their subsequent impact on sediment dynamics, may contribute to the rapid climate and CIE recovery from peak-PETM conditions.

We reconstruct the calcareous nannofossil response to the Eocene-Oligocene Transition (EOT)-the most significant climate transition of the Cenozoic-in the Indo-Pacific Warm Pool. Data from south central Java consist of species relative abundance counts of well-preserved nannofossil assemblages. From the late middle Eocene to early Oligocene species biodiversity declined, with the most rapid species loss occurring across the latest Eocene rosette-shaped discoaster extinction event (DEE;~34.44-34.77 Ma). A decline in abundance of oligotrophic indicator taxa across the DEE indicates increased nutrient supply to the tropical surface ocean in the early stages of the EOT. The mean lith size of reticulofenestrids also increases across the DEE driven by a marked reduction in the abundance of small Reticulofenestra morphotypes (<3.5 μm). There is no preferential loss of larger Reticulofenestra cell sizes (coccoliths > 8 μm) across the EOT, indicating that coccolith size was apparently not limited by atmospheric CO 2 concentrations at this time. Overall, the main phase of tropical phytoplankton ecosystem change preceded the interval of rapid Antarctic ice sheet growth and is closely associated with the biotic perturbations that define the start of the EOT. This suggests that enhancement of Southern Ocean controls on tropical ocean biogeochemistry and nutrient pathways may have played a role in triggering the transition to an icehouse climate state.