Welcome to the Meghalayan
- Taariq Sheik
- Sep 4, 2018
- 7 min read
The age in which we live has officially been renamed, but some things, unfortunately remain the same.
Get out the fireworks, the ball (read golden spike) has dropped, we’re officially in a new age. Except the new age, or stage, began 4250 years before 1950. Thats right, we’re in the Meghalayan.
While for many of you this may not be a reason to break out the champagne and make promises to yourself that you’re never going to keep, it has been a major source of discontent among academics. Before we can delve into the depths of that discontent, I think a bit of context is required.
There exists an organisation steeped in mystery, the guardians of time, the International Commission on Stratigraphy (ICS). Alright, I’ll admit thats a bit of an anti-climax, but bear with me. The ISC is a group of mysterious individuals who meet every ten years to decide how geological time is packaged.
You see, we currently live in the Holocene Epoch (for those of you looking for the song by Bon Iver please redirect here), which was preceded by the Pleistocene. The ICS is the organisation that decides when these Epochs, Eras and Ages start and end. This is done by looking into Earth’s very own diary (don’t worry we have a warrant), stratigraphy.
You see, while ‘Orges are like onions’ so too is the Earth. The crust of the Earth consists of multiple layers (stratigraphy) of rock formed over hundreds of millions of years. These layers of rock, and more recently soft sediments, record the physical and chemical history of our dear old planet. New periods in this history are defined by significant physical and chemical changes in the stratigraphy.
So actually, the ISC aren’t so much the guardians of time, but more the guardians of history. Geological time is officially subdivided by the identification of Global Boundary Stratotype Section sand Points (GSSPs). These are specific sections of stratigraphy, in specific locations that record the physic-chemical changes that define a new period of Earth history and are colloquially referred to as ‘golden spikes.’
Prior to the most recent amendments by the ICS, the most recent ‘golden spike’ marked the transition from the Pleistocene to the Holocene. The Pleistocene was a period of about 2.8 million years that experienced successive periods of glacier advance and retreat, so calling the Pleistocene the ‘Ice Age’ is actually inaccurate as there were numerous Ice Ages and Not Ice Ages (Hot Ages? Water Ages?) in the Pleistocene.
This ‘golden spike’ can be found 11784 years ago in the NorthGRIP ice core from central Greenland. The boundary is marked by chemical indications of glacier ablation (melting) following the Younger Dryas event, a marked period of cold and glacier advance that marked the last shiverings of the last ice age of the Pleistocene.
The most recent meeting of the ICS has now introduced two further ‘golden spikes,’ dividing the Holocene Epoch into three stages, the Greenlandian 11784-8200 BP (before present), note that due to the quirks of stable isotope dating BP refers to before 1950, Northgrippian 8200-4200 BP, and the Meghalayan 4200-0 BP.
The process of subdividing the Holocene actually began 10 years previously when Prof. Mike Walker from the University of Wales, Lampeter, was commissioned to identify ‘golden spikes’ to subdivide the Holocene. In 2012 he published the formal subdivision of the Holocene, which was officially ratified by the ICS earlier this year.
According to Walker, identifying a golden spike to divide the earliest part of the Holocene, immediately following the last ice age was easy. A massive glacial lake outburst 8200 BP flooded millions of litres of freshwater into the North Atlantic Ocean, disrupting global circulation patterns and resulting in globally cooler conditions. These cooler conditions are captured in the chemistry of the NorthGRIP ice core sequence and marks the boundary to the Northgrippian Age.
This event is well constrained (in time) and well realised in terms of environmental effects in high latitudes, with lake and ice core data pointing to cooler, drier conditions and the expansion of boreal forest (pine and birch) at the expense of deciduous trees (hazel, oak). However at lower latitudes, while records do indicate more arid conditions around the boundary, the event is poorly constrained in comparison high latitude records.
A somewhat similar picture is painted, albeit with a different colour palette, with the boundary between the Northgrippian and the Meghalayan.
The recognition of the Meghalayan Age, beginning at 4200 BP is twofold. Archaeological evidence points to significant social upheaval in complex agricultural societies from Egypt to India and China. Chemical evidence from speleothems (layered stalactites in caves) and lake sediments also point to arid conditions centred around 4300 and 4100 BP due to disruption of monsoonal circulation systems.
It is suggested that these arid conditions contributed to the destabilisation of agricultural civilisations in the mid latitudes. The ‘golden spike’ for the Meghalayan is the Mawmluh cave speleothem record which indicates significant aridity centred around 4300 and 4100 BP, with the 4200 BP date for the spike occupying the midpoint of the event.
The Meghalayan Age however, is not without its detractors. Distinguished researchers argue that the dating for the event is poorly constrained and the aridity event is not manifested globally. With Raymond Bradley from the University of Massachusetts calling the 4200 BP boundary ‘baseless.’
Other researchers urge caution, and stress the complexity of attempting to draw conclusions between archaeological and palaeoclimatic data. Evidence for significant aridity at the boundary at high latitudes does seem to be lacking, with only scattered evidence for the event in central-northern Europe.
Global analyses of palaeoclimatic data also identifies no significant climatic event centred around 4200 BP. However these analyses might be skewed by an overrepresentation of records from high latitudes.
Given that spatial and temporal uncertainties exist with both Holocene subdivisions I wonder why all the critique is reserved for the Meghalayan? A lot of the criticism is a response to the failure of the ISC to recognise the Anthropocene, the age where human activities are recognised as driving global climatic change.
Prof. Mark Maslin was particularly scathing, suggesting that the ICS definitions go against scientific consensus of the Anthropocene and contradicts the Anthropocene Working Group, a subcommission of the ICS.
While I believe there is little doubt that we are in the Anthropocene, with anthropogenic greenhouse gas emissions driving unprecedented climatic change, the recognition of the Anthropocene by the ISC is an entirely different matter.
As mentioned, the ISC requires a golden rod (GSSP) in the global stratigraphic record to recognise the transition to the Anthropocene. Will this golden rod be microplastic deposits in marine sediments? Or increased greenhouse gas concentrations in ice cores? While that debate is still ongoing, it is important to note that the subdivision of the Holocene in no way precludes the future recognition of the Anthropocene.
In fact, the recognition of the Meghalayan, in part due to the impact of climate change on past societies, is a step in the right direction as it recognises the relationship between humans, climate and the environment.
It’s also not as if the Holocene hasn’t been divided before. There’s been little consternation to the ‘chronozone’ classification of the Holocene that divides the Epoch into five zones (Preboreal, Boreal, Atlantic, Subboreal and Subatlantic) based on high latitude vegetation development.
The Holocene has also been informally divided into early, middle, and late stages since it’s inception. Max Berkelhammer from the University of Illinois says that these informal divisions have led to a lot of confusion with, ‘Some people say(ing) the late Holocene was warm, other people say(ing) the late Holocene was cold, they both might be right because they’re using this term late Holocene inconsistently.’
In this way, a formal division of the Holocene is essential to bring consistency to a field, that myself having been a member of, is remarkably inconsistent.
So why then is there all this furore over the Meghalayan? When considering the uncertainty surrounding both the Holocene subdivisions and that the definition of the Meghalayan does not preclude the recognition of the Anthropocene, it becomes important to examine not only the scientific basis for the boundaries, but also the social context into which these boundaries have been launched into.
Given that the recognition by the global political elite of the climatic forcing of anthropogenic greenhouse gas emissions, and secondly, the large orange, oily tantrum (read Trump) in response to this, the failure of the ISC to recognise the Anthropocene reveals an academic community blind to its social responsibility.
But, as previously mentioned, recognition of the Meghalayan in no way precludes the future recognition of the Anthropocene provided the identification of a suitable golden rod. Say what you want in critique of academic bureaucracy and I’ll probably agree with you, but science only moves forward with the slow creep of research and review.
With this context, I think its important to note that Europe and North America have been the traditional hubs of geoscience research, conducted predominantly by white males. Indeed, across the past 24 ages of Earth history, spanning the last 66 million years since the end of the Cretaceous, only three other ages, apart from the Meghalayan, have been named after a regions outside of Europe, and those three are all in North Africa.
The boundaries of the Greenlandian and Northgripian are both well constrained (temporally) and physical impacts well realised in Europe. The Meghalayan boundary on the other hand poorly constrained at mid-high latitudes, with more evidence for significant climatic disruption in monsoonal regions.
It seems to me that dissatisfaction with the Meghalayan is really a response by prominent white researchers to establishing a stratigraphic age based on a climatic event that was focussed outside out Europe or the high latitudes, and using a marker outside the traditional hubs of geoscience research.
Furthermore I sense a certain discontent among researchers that the age we currently live in being named after a region outside Europe or North America. For instance, William Ruddiman, a prominent and somewhat controversial researcher at the University of Virginia who is the progenitor of the early Anthropocene hypothesis, which suggests that early agriculture and landscape transformation should be used as a marker for the Anthropocene says, ‘I’m not going to remember what they named it, I’m never going to use the name, and I’m guessing most scientists will not. To me? It’s silly.’
It seems that despite entering a new age of time, Eurocentricity, and metric based judgements on the quality of geoscience research persist.
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