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Stratigraphy, Sedimentology and Palaeontology
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Alena Ebinghaus

After graduating at the University of Bonn in 2010, Alena Ebinghaus took up a PhD project at the University of Aberdeen, examining inter-lava sedimentation and plant ecosystem development in the Columbia River Flood Basalt Province, Washington State. Following her graduation in 2014, Alena joined the University of Aberdeen as a post-doctoral researcher. In her current research, Alena focuses on the understanding of continental environments during past rapid climate warming, such as the Early Danian Dan-C2 event and the Palaeocene-Eocene Thermal Maximum. Since 2017, Alena has served as the Early Career Scientist (ECS) representative of the SSP division.

Palynological applications to sedimentology – a BSRG workshop

Palynological applications to sedimentology – a BSRG workshop

The 2019 BSRG workshop ‘Palynological Applications to Sedimentology’ was held at the University of Aberdeen from the 17th-19th February. The trip was led by palynology experts Dr. Adam McArthur (University of Leeds), Dr. Alena Ebinghaus (University of Aberdeen) and Dr. Manuel Vieira (Shell), organised by Dan Tek from the University of Leeds, and sponsored by the International Association of Sedimentologists (IAS) and Shell. Twenty researchers from institutions across Europe flocked to the Granite City for an introduction to the weird and wonderful world of palynology.

After a day of travel and an evening of informal introductions, the workshop began in the morning of the 18th February with a scenic walk, guided by Adam, from the accommodation to the University. The workshop kicked off with an introductory presentation by Adam McArthur, defining palynology, the distinction between palynology and palynofacies, and the applications of both techniques to a variety of problems in almost all sedimentary environments. We then headed to the sample preparation laboratory for an overview of the sample preparation process. Due to the time-consuming and dangerous nature of palynology sample preperation using various acids, best practice was covered with the help of props, and a strong emphasis was placed on health and safety.

Adam and Ilse, the palynology lab technician, explaining the dangers of hydrofluoric acid.

The trip to the lab was followed by a core workshop led by Alena Ebinghaus on core from the Boltysh Crater lake, Ukraine, from which palynological studies have been used to uncover the mysteries of its post-K/Pg boundary fil. The participants were given some time to examine the core and note any interesting features before Alena took the group through the interpretation and explained the palynological work that has been undertaken on the core.

Alena discussing the features in this fascinating core with the group.

After lunch it was time to get hands-on with the critters! Microscopes were set up and the eager trainee palynologists spent some time exploring the microscopic world on the slides. Palynological slides were provided first by Alena, who has used this palynology data to investigate terrestrial lava-sediment interactions on drainage systems in Washington State, USA. The participants were challenged to identify and sketch the types of pollen and spores. Next, Adam provided three slides to each group from different deep-water sub-environments from outcrops in Baja California, Mexico, to showcase the value of palynofacies in palaeoenvironmental reconstructions.

Participants trying to identify the various types of pollen, spores and other organic matter under the microscope.

To top this busy day of learning, the participants were then invited to discuss their work specifically with the course leaders on a one-to-one basis. These conversations carried on as the group headed into Aberdeen for a meal and to the pubs to sample some of Scotland’s finest whiskeys.

Our group enjoying a meal at Manuel’s favourite local eateries.

The second day, run by Manuel Vieira, was industry focused and aimed to exemplify the key application of palynology to wider biostratigraphy, and to subsurface interpretation. Manuel first gave an introduction to biostratigraphy, using examples to demonstrate the drastic changes that can be made to subsurface well correlation based on biostratigraphy and palynology. We were then given an industry-style exercise whereby two logs were correlated using biostratigraphic and palynological markers, uncovering a drastic change in reservoir properties. After a wrap up session and some feedback it was time to say goodbye to our fellow course mates and leaders.

(left) Participants trying to identify their key horizons from a biostratigraphic chart; (right) a completed biostratigraphic chart being checked by Manuel and Alena.

A massive thanks to our course leaders Adam McArthur, Alena Ebinghaus and Manuel Vieira for providing such an insightful, engaging and fun workshop, and to all who attended the workshop!

Photographs taken and text written by Daniel Tek (ee11dt@leeds.ac.uk), University of Leeds.

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).

 

 

The microworld of the past

In my last blog, I described the diverse world of pollen and how palynology – the study pollen, is used in geosciences. Today, I turn to another microcosmos: that of finest layers deposited at the bottom of a lake.

A large majority of geoscientists would tell you the best part of their job is field work. Despite sometimes harsh weather conditions, long hikes in wind, rain or merciless sun, many geologists enjoy the outdoors and look forward to a great rock exposure. While I very much enjoy field work myself, some of my current research brings me to the core lab at best. Here, at the University of Aberdeen, we have access to a 400 m long core of rock, which was drilled 10 years ago with the help of the Open University and University of Kiev in the Ukraine – a core drilled in the centre of the so-called Boltysh meteorite impact crater.

Part of the core recovered by drilling ancient lake sediments in the Boltysh meteorite impact crater, Ukraine.

The Boltysh crater formed about 65 My ago, which brings it in the same age range as the more prominent Chicxulub impact, which by some scientists is considered as the cause for the extinction of dinosaurs. The Boltysh crater, however, probably formed a few thousand years prior to the Chicxulub impact, and is of much smaller size. What makes this crater so interesting for us is that shortly after its formation, a lake began to form at the crater bottom, slowly filling up the entire crater with finely layered lake sediments over a period of nearly 1 million years. Importantly, these sediments cover the first 500.000 years of the earliest Palaeogene age (=Danian), which is known for its unstable climatic conditions. Understanding how climate and environment changed in the past is a crucial step in better understanding modern climate change and its short- and long-term impact on Earth.

Modern lakes typically produce very fine layers of debris at the bottom, often less than 1 mm thick. These layers, sometimes referred to as varves, may vary from year to year, and even from season to season, similar to concentric tree rings.  Ancient lakes and their deposits show very similar lamination of sediment. That way, both modern and ancient lake sediments may give detailed insights into how environment and climate changed over a few years or decades – and this even from many million years ago!

Slide scanner image of very fine lamination formed during deposition of sediments at lake bottom, due to seasonal changes in sediment supply and composition (Boltysh meteorite impact crater).

The core recovered from the Boltysh meteorite impact crater reveals lamination as fine as 0.08 mm. Individual layers – or laminae, therefore need to be examined with a high-resolution microscope or core scanner to distinguish slight changes in mineral, chemical and grain size composition, as well as fossil flora and fauna content. These information are used to reconstruct how environment and ultimately climate changed through geologically short periods of time. Although 65 million years old, this core contains valuable information on how Earth responded to climate change in the past – which helps to better predict changes of our environment in modern and future times.

Plant fossil (here part of a conifer), Boltysh meteorite impact crater. Core width c. 8 cm.

You wouldn’t go in the early basement during the upper afternoon, don’t you?

I remember it perfectly. It was 13 years ago, while writing my first manuscript, I was first confronted with that thing that challenges a lot of junior stratigraphers, especially when they are not a native English: Geochronology vs. Chronostratigraphy! Or to simplify, how to properly distinguish time and time-rock units in your writings.

Several papers have been published on this subject, out of which I would recommend the recent Zalasiewicz et al. (2013). But, although these papers do provide a very clear scientific explanation on this subject, I always remember myself 13 years ago and how difficult it was for me back in those days to understand these concepts!

So, is it that difficult? Or is there an easy way to spot the light at the end of the tunnel? Well, if you have spotted the oddness in the title of this blog, the good news is that you have already made 3/4 of the way. Of course, the trick is in the use of early/late vs. lower/upper, that is to say on the distinction between time (geochronology) and space (chronostratigraphy), respectively.

Let’s have a little test to check that. Which of the following five sentences are wrong?
1. The late Bajocian is 500m-thick in this region.
2. The upper Bajocian can be correlated throughout this region.
3. The lower Bajocian has experienced environmental changes.
4. A carbon cycle perturbation occurred during the early Bajocian.
5. The lower Bajocian carbon isotope excursion.

Without having too much suspense: it’s the sentences 1 and 3 that are wrong.
In sentence #1, the term “late” is used whereas the sentence makes reference to time-rock unit, i.e. chronostratigraphy. Here, Bajocian refers to the thickness of the sedimentary sequence, so one should use the term “upper”. However, if you insist on using “late”, then you should write the sentence as following: “The thickness of the sedimentary succession dated from the late Bajocian is 500m”.
In sentence #3, we have the opposite case, i.e. the use of “lower” while referring to time, i.e. geochronology. It is as odd as “having a meeting in the upper afternoon”.

There you go, you have done 3/4 of the way. What about the last quarter? The answer is in sentence #5. It is indeed correct, and refers to the carbon isotope excursion you have measured in the Lower Bajocian, i.e. in the section you have worked on. But writing “the early Bajocian carbon isotope excursion” is also correct, but this time it refers to the carbon cycle perturbation that has occurred during the early Bajocian. You know… the one that is recorded in the lower Bajocian! But never say that it is recorded in the early Bajocian, that would be wrong.

Reference:
Zalasiewicz, J., Cita, M.B., Hilgen, F.J., Pratt, B.R., Strasser, A., Thierry, J. and Weissert, H. (2013) Chronostratigraphy and geochronology: A proposed realignment. GSA Today 23, 4–8.

Author: Dr. Stéphane Bodin, University of Aarhus