The Cenomanian
A long-term research effort and goal is a better understanding of the Cenomanian stage of the Cretaceous period. The Cenomanian stage (93.9 - 100.5 mybp) is a particularly interesting time period which includes points when Earth's temperature and sea-levels were at their very highest. It is thought that sea-levels could have been as much as 200 metres higher than they are at the present day and annual mean surface temperatures 10-14 degrees higher than today. Two very significant oceanographic events occur at the beginning and the end of the Cenomanian that are also relatively rare in Earth's long history. These are called Oceanic Anoxic Events (OAEs) and represent significant periods of geological time where the worlds seas and oceans were significantly reduced in the amount of dissolved oxygen in the water. This, generally, was not favourable to life in the waters (although a few fossil groups seem to have thrived) and many marine organisms became extinct, or at least had their distribution considerably restricted.
In order to place these events, as well as other changes that took place in the Cenomanian, it is necessary to build a robust framework of the rocks deposited in both space and time. There is no one-size-fits-all approach possible here. Geologists use a number of different techniques, some of which are closely related to others, and some less so. Such frameworks can be calibrated to absolute values of geological time (numerical ages) or they can be a relative framework (e.g., "event B occurred before event C but after event A"). The best frameworks are, of course, combinations of both. These approaches also lead to a necessary by-product of the work - the idea of synchronicity. Let's imagine we have a number of separate rock sections in different localities around the world, but all of which contain a geological 'signal" that tells us they each represent a fall in sea-level. How do we know the 'signal' in the rocks represents the same sea-level fall? If the sediments below the signal in each locality contain evidence of "event B" and all the sediments above it contain evidence of "event C" then we have demonstrated that the sea-level fall was synchronous between all of the localities (i.e., took place everywhere at the same time). Knowing this, we can try and work out what was going on to cause sea-levels to fall... everywhere, at this time.
Moreover, armed with this information, we can now predict that anywhere a rock section of a similar age is located, it should have evidence for the same sea-level fall that we have seen before. It may also have those valuable rocks associated with the sea-level fall nearby.