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The Plastocene – Plastic in the sedimentary record

The Plastocene – Plastic in the sedimentary record

The University of Hull was privileged to host the annual British Science Festival in 2018. One of the key events was the Huxley Debate, which brings together world-leading experts to discuss a pressing issue facing society. The theme in Hull was “what do we do about ocean plastics?”. As part of the discussion, Professor Dan Parsons, Director of the Energy and Environment Institute, suggested that in the future we will see the evidence of our plastic waste in the sedimentary record, and that the emergence of this in the record could mark the boundary between Holocene and Anthropocene.

Professor Parson’s suggestion prompted one journalist to remark, in jest, that a better name for the new epoch would be “the plastocene”. It may have been a moment of mirth, but the feasibility of the emergence of the plastocene should not be discounted.

Plastic pollution is a huge issue. You will have undoubtedly heard the key statistics over and over by now – 12 million tonnes of the stuff enters the world’s oceans every year, and at that rate there will be more plastic than fish in them by 2050. Plastic is designed to be virtually indestructible and never really disappears, instead breaking down into smaller and smaller pieces. It is possible that the only way we will ever get it out of the oceans is to wait for it to settle on the ocean floor and be buried – something we might be waiting a long time for – it floats.

Plastic deposits are already being found – some have useful (but unwelcome) side-effects such as marking the extents of flood events by forming wrack lines. For example, rubbish deposited by storms and tsunamis has been used to date the events (using packaging and labels) and determine the flood extents. On a recent visit to the south of Spain as part of an undergraduate field trip I observed wrack lines formed of tiny fragments of multi-coloured plastic. Such deposits can get buried, preserving the records with them.

Plastic wrack lines left behind in a dry river in the south of Spain (Authors own photos). Simon Reeve’s documentary ‘Mediterranean’ highlighted the issue of microplastics in this region of Spain, showing plastic sheeting buried within a dried river bed.

Plastics have already been found being formed into rocks. Corcoran et al (2015) observed a new type of rock dubbed ‘plastiglomerates’ around the beaches of Hawaii. They formed when plastics melted and fused with natural materials, such as beach deposits and volcanic rocks. They found no evidence of recent lava flows so suggested that the plastiglomerates were formed by the deliberate burning of the plastics.

The lithification processes behind beach and marine carbonate cementation can be extremely rapid, forming rocks in as little as a year, which means evidence of human activity is preserved and can be used for dating – examples include glass drink bottles and World War II debris. In the future we could end up seeing plastics preserved in these carbonate cements.

However, despite all of this it is unlikely our ancestors, or whatever might inherit the planet from us, will observe this period of the sedimentary record and refer to it as the plastocene. Plastic pollution is not the only pressure we are exerting on the planet, it is not even the most significant. We have also been making our mark on the sedimentary record for millennia, with the earliest mining and smelting activities resulting in spikes of lead in deposits to the nuclear tests of the 1950s leaving an imprint of Plutonium 239. We cannot isolate plastics from our impact on what truly is the Anthropocene.

Mining the Carboniferous in the Ruhr area (Germany)

Mining the Carboniferous in the Ruhr area (Germany)

During the upper Carboniferous period (Namurian, Westfalian and Stephanian)  large areas of central western Germany were covered by coastal swamp forests dominated by Lepidodendron und Sigillaria. Periodic marine and fluvial transgressions caused the swamps being regularly buried by siliciclastic material, resulting in up to 5500 m thick successions of alternating organic-rich and clastic-rich sedimentary rock. The organic-rich packages were later subject to coalification producing up to 100 individual coal beds in the area of the river Ruhr. Presumably, initial (private) coal mining started during the Middle Ages, however, with the onset of the Industrial Revolution, commercial mining started and peaked in the 19th until mid of 20th century with more than 120 million tons of coal mined per year. Today, only a few pits are mined sporadically, with the last pit (Zeche Proper Haniel) ceasing service this year.

Upper Carboniferous plant fossils (probably Coniferous) found in coal seams, (Esperschörpen Siepen, Germany).

 

 

Brachiopods in a changing planet: from the past to the future

Between the 10thand 14th of September 2018, the 8thInternational Brachiopod Congress took place in the prestigious venue of the University of Milan, after the previous editions held in Melbourne (Australia) in 2010 and in Nanjing (China) in 2015. It was the first time, since its foundation over 35 years ago, that this important conference was hosted in Italy.


The Congress was attended by 150 participants from universities and research institutes from all over the world (Argentina, Armenia, Austria, Belgium, Canada, China, Czech Republic, Denmark, France, Germany, Hungary, Iran, Israel, Italy, Japan, New Zealand, Poland, Russia, Slovakia, Spain, Sweden, United Kingdom and USA).

 

Brachiopods are a group of marine invertebrates known since the Cambrian, that show a high biodiversity and a dominant role mainly in the Palaeozoic oceans. They are considered one of the best biomineral archive, due to the unique characters of their shells, to understand the evolution of marine calcifiers during climate and environmental changes in the recent and deep geological past.

The topics of the Congress have touched all aspects of the study of brachiopods, from systematics and evolution to biostratigraphy, palaeoecology, palaeobiogeography, up to the biology of recent taxa. Particular emphasis was devoted to research on mass extinctions, biomineralization and geochemistry, as well as new methods of microscopic investigation with the latest equipment in this field.

Interesting talks included new findings on the process of shell formation, and on the steps of its possible diagenetic alteration, and multidisciplinary studies on how brachiopods and their shells respond to ocean acidification both in culturing and natural environment and in the geological record. Advancements in brachiopod research were also testified by new discoveries on their phylogeny and taxonomy, as well as on palaeoecology and taphonomy, and on how they could survive and recover after biotic crises, such as the big ones of the end-Ordovician or the end-Permian, ending up with new approaches in shell geochemical analyses.

The abstract volume of the congress can be downloaded at  http://permian.stratigraphy.org/files/20180828212711700.pdf

 

3D model of the brachiopod species Magellania venosa, made in the frame of the BASE-LiNE EarthProject

 

In addition to the oral and poster scientific sessions and two prestigious plenary lectures, the Congress was preceded and followed by three field trips (Spain, United Kingdom and Sicily), as well as by two mid-congress day excursions only a short distance from Milan (Castell’Arquato and Grigna Mountains). Participants had the possibility to discover the wonderful fossiliferous localities of Italy and Europe.

 

Sometimes released into the background, invertebrate macropalaeontology has a high scientific potential; macrofossils are excellent archives of data which help palaeontologists to understand the lesson from the geological past to interpret our future. The 8thInternational Brachiopod Congress just held in Milan, with its numerous oral and poster presentations, is a clear evidence of that. The brachiopod community has proved to be very active, with a lot of young students and researchers involved in the development of new studies and projects. An example of that is the BASE-LiNE EarthProject, founded by the European community with 21 partners (lead by GEOMAR, Kiel), which produced very innovative multi- and interdisciplinary researches (https://www.baseline-earth.eu/)

 

So…keep an open eye on macropalaeontology latest discoveries!

 

Chair of the Congress: Lucia Angiolini & Renato Posenato

Scientific Committee: Álvarez Martínez F., Angiolini L., Brand U., Carlson S.J., Cusack M., Eisenhauer A., Harper D.A.T., Holmer L., Garcia Joral F., Lüter C., Pérez-Huerta A., Posenato R., Shen S.

Organizing Committee: Crippa G., Brandolese V., Garbelli C., Henkel D., Romanin M., Ye F.

 

This post was written by Gaia Crippa and Lucia Angiolini with revision by Cinzia Bottini

 

Gaia Crippa is a post-doctoral researcher at the University of Milan (Department of Earth Sciences, Italy).

Lucia Angiolini is full professor at the University of Milan (Department of Earth Sciences, Italy).

Glacial grooves from the Laurentide Ice Sheet (Québec, Canada)

These impressive glacial grooves observed along the North Shore of the St. Lawrence Estuary (Québec, Canada) were carved into the crystalline bedrock by the Laurentide Ice Sheet.
The grooves mark the basement of a complex sedimentary system known as the Tadoussac Delta, lying at the mouth of the Saguenay Fjord and intimately tied to the Late Pleistocene-Early Holocene deglaciation of the area.
The exact glacial dynamics that created these straight regular marks has still to be constrained. For more information on the formative processes and the general context, keep an eye on a forthcoming paper by Lajeunesse et al…
These grooves were visited this summer during a fantastic field trip of the ISC2018: “Landforms, sedimentary facies and stratigraphic architecture of a deglacial, forced-regressive context: the Québec North Shore” by Pierre Dietrich, Patrick Lajeunesse and Jean-François Ghienne. http://www.isc2018.org/field-trips#POST