"As stratigraphers, we require criteria to map the Anthropocene with relevant and consistent meaning. Presently, we are left to map a unit conceptually rather than conceptualizing a mappable stratigraphic unit."The above quote (emphasis added), written by Autin and Holbrook (2012) in an article in GSA Today, forced me to question some fundamental arguments in this debate. Is the Anthropocene a term rooted in pop culture, based more on conceptual meaning in search of a stratigraphic signal, as opposed to starting with a distinct stratigraphic record? Finney (2014) asked the very same question, and I find his opinion akin to mine. The more I become involved with the Anthropocene debate in this blogging journey, the more I am questioning everything I once believed at face-value without a second thought. The idea behind this post is rather like the famous question of what came first, the chicken or the egg? In this instance, should concept come before stratigraphic evidence?
A defining feature of the Anthropocene, distinct from other units of geologic time, is that the proposed epoch is in the present and continually evolving. Therefore, instead of looking back in retrospect at fossils and stratigraphic evidence, the conceptualising step must come first, with stratigraphic evidence following later. Whether this is the 'correct' way to classify a new unit of geologic time is dubious. Historically, changes in stratigraphy have been identified, and then conceptual units of time have been assigned to these clear shifts and events in the strata. In our present day, the world has identified a new concept, one which views humanity as a centrally dominant geologic force, and now we're searching for a stratigraphic signal to fit that concept. Perhaps this signifies a time for change in how the Geologic Time Scale (GTS) should be constructed in a present-day mindset, recognising that fossils and stratigraphic evidence can become secondary to conceptual assignments.
Finney (2014) continues this philosophical debate by questioning the conceptual basis of the GTS, asking whether it is suitable to be applied to 'chronometers of recorded and future human history'. As so much of what constitutes the Anthropocene is in the present and near-future, should it formally become part of the GTS, considering that all units currently recognised are events which occurred deep in the past (Finney 2014)? I agree with Finney that this is a very important question that needs addressing by the AWG, but I do not agree that the Anthropocene (or any other future time intervals) should be written off from formalisation just because it has not occurred in the deep past. In my eyes, the GTS should modernise to accommodate for new periods of time which will likely come to fruition during humanity's existence on the planet. This may be as simple as providing alternative time resolution intervals which acknowledge shorter events and ages (e.g. centuries to millennia) within larger chronostratigraphic units (e.g. epochs and periods). Clearly the time resolution currently used on the GTS (millions to billions of years) would scarcely recognise the Anthropocene, a blip of time in Earth's 4.5 billion year history. So, should the GTS downscale to additionally accommodate smaller, yet important, intervals of time, extending the use of GSSAs? Or, should the GTS refuse to formalise these smaller events and continue formalising only those longer time intervals with robust GSSPs and a clear stratigraphic record?
Crucially, the Anthropocene is the first proposed geologic interval whereby the focus itself (humanity) is able to influence and change the very nature of the time wished to classify. This brings me onto my next big question to address: is the Anthropocene a unit of human history rather than Earth history?
Great post! You stated "humanity as a centrally dominant geologic force". Would you mind explaining further how, we as humans, have altered the worlds geology. Looking foward finding out more about the subject!
ReplyDeleteThanks, Charlie! There are so many ways in which human activity has altered Earth's geology, though what we are seeing now is just the beginning in my opinion. For example, there are layers in the strata which show fallout from radioactive isotopes (from nuclear weapons and bomb tests) and species extinctions will be shown in fossil layers in rock strata. However, human dominance of Earth Systems is shown in other ways such as recorded CO2 and CH4 increases in ice cores and lake sediments, and coral bleaching from acidification of oceans.
DeleteAnother interesting signal for human activity in geologic layers is the presence of spheroidal carbonaceous particles (SCPs) in geologic layers - created as a byproduct of fossil fuel combustion - which could act as a GSSP for the Great Acceleration. I'll be revisiting this fascinating work by Neil Rose at a later date.
I hope that has answered your question! :)
You pose a great question at the end of your blog; I suppose it's at the heart of the decision at whether or not we should label the Anthropocene as a new epoch, as every other epoch has been focused on earth history, not a the impacts of a dominant species. Do epochs become species-centric or earth-centric, or does it depend on which is the most significant!
ReplyDeleteThanks, Louis! I will focus more on that question in my next blog post. You are correct, it is difficult to distinguish whether the Anthropocene has become more of an anthropocentric assignment of human superiority, or if the Anthropocene warrants enough change in Earth History to be formally ratified.
DeleteWe are in uncharted territory where potential new epochs (now and in the future) will be largely influenced by humans - do we accept this change to the way the geologic timescale will be constructed, or stick to traditions? It's a tough one!