Present the current status of unconventional resources around the world, including a broad perspective to better understand the important palaeogeographic, tectonic and burial history that lead to significant accumulations and production from unconventional reservoirs.

The Eocene includes the warmest time interval in the last 65 million years, yet there is still discussion about how much warmer that climate was and how warmth was distributed across latitudes. Oxygen isotope data from deep-sea microfossils are the industry standard for interpreting paleotemperatures, but are limited by uncertainty in both the composition of local seawater from which the carbonate precipitates and in the season of growth of the precipitating organisms.

Accretionary carbonate from marine shelf bivalves can contribute to the resolution of these difficulties because mollusk shells allow for the recognition of seasonal biases in growth and produce enough carbonate to enable independent temperature control using clumped isotopes analysis, a technique currently limited to large sample sizes.

In addition, shells can be collected in situ with sedimentary organic matter, allowing additional temperature control from tetraether analyses. I will present δ18O data through the Eocene from both Antarctica and the US Gulf Coast, many of which are seasonally resolved. Temperature is independently determined in key stratigraphic horizons with these additional proxies, and the resulting water compositions are then used to determine paleotemperatures through time from the more extensive δ18O dataset. Results reinforce the concept of polar amplification of greenhouse warming and show that, while the high latitudes were certainly warm, they may not have been as hot as some recent studies have suggested.

Present the current status of unconventional resources around the world, including a broad perspective to better understand the important palaeogeographic, tectonic and burial history that lead to significant accumulations and production from unconventional reservoirs.

Paleoclimate work in Earth’s deep past has been limited by uncertainty about the meaning of unexpectedly low δ18O values from ancient marine carbonates. Increasingly negative values with increasing age could indicate very warm depositional temperatures, more negative seawater compositions, or pervasive alteration of the original carbonate.

A significant impediment to progress has been the inability to convincingly demonstrate that the oxygen isotope values of carbonate retain their primary signal of depositional conditions. High-resolution microsampling of accretionary shell carbonate may offer a resolution to this aspect of the debate. Shells that demonstrate seasonal variation in isotope values along the growth trajectory can be more reliably interpreted as primary.

Micromilled data from early Permian bivalves from high paleolatitude settings in SE Australia each show clear and consistent seasonal variation over 5-6 years of shell growth. Independent temperature control from associated glaciomarine sediments and glendonites require winter temperatures near freezing and therefore allow for determination of seawater δ18O. Shells arrayed over 11° of paleolatitude illustrate a trend toward more negative winter shell values and decreasing seasonal amplitude of water temperature moving toward the pole.

Data suggest seawater values decreased from -3 to -5 per mil with increasing latitude, significantly more negative than modern open marine values. This implies a much steeper gradient in the composition of seawater with latitude than today, mixing of small but consistent amounts of depleted meltwater, or an overall more depleted ocean than today. Additional sampling to increase geographic coverage will hopefully help discriminate among these possibilities.

Present the current status of unconventional resources around the world, including a broad perspective to better understand the important palaeogeographic, tectonic and burial history that lead to significant accumulations and production from unconventional reservoirs.

Seasonality of temperature variation has been somewhat of an enigma for paleoclimate research. The vast majority of studies on ancient climate purport to recover some approximation of ‘mean annual’ temperature, yet rarely is there any way to verify this. The unparalleled gold standard of climate records are those derived from the chemistry of marine microfossils, but unacknowledged seasonal differences in growth can give rise to biased mean values.

In addition, while mean annual temperature is a useful descriptor of climate, most organisms are limited instead by temperature extremes. Interpreting the impact of climate change on biological systems, often the ultimate goal of climate research, therefore requires knowledge of seasonal maxima and minima.

Lastly, seasonal range is a parameter that could be very useful in evaluating the results of climate models, but few data are available for comparison. Accretionary biogenic carbonates, such as the shells of fossil mollusks, offer an opportunity to recover seasonality in Earth’s deep past. High-resolution sampling along the growth trajectory can yield a detailed record of the temperatures experienced by an individual throughout some portion of its lifetime. Capturing a number of years within a particular stratigraphic horizon yields not only a robust measure of seasonal range but also information about interannual variability. With adequate coverage, both of these variables can be examined in a temporal or geographic context to see how they relate to changes in mean annual temperature as well.

The approach is not without its challenges – sampling resolution can smear the seasonal signal, organisms do not necessarily accrete carbonate throughout the year, and the depth at which benthic organisms live correlates roughly with the seasonal range they experience. Nevertheless, with a bit of care, these kinds of data can offer new insights on the climate system and the anticipated consequences of global change.