Stratigraphy, Sedimentology and Palaeontology

Geosciences Column: Pollen tells a 7300 year old story of Malta’s climate and vegetation

Geosciences Column: Pollen tells a 7300 year old story of Malta’s climate and vegetation

Figuring out what the climate was like, and how it changed, throughout Earth’s history is like trying to complete a 1000 piece puzzle. Except that scientists usually don’t have all the nuggets and building a comprehensive picture relies on a multidisciplinary approach in order to fill in the blanks.

This is particularly true during the Holocene, which spans the last 11,700 years of the Earth’s history, and began at the end of the last ice age. It marks a time of significant climate change across the planet, coupled with changing vegetation dynamics and the emergence of humans, who even at that early time, started leaving their mark on Earth. Bringing together all the evidence to build a complete picture of what the environment looked like is no easy task.

The Mediterranean, in particular, is considered a hot-spot for changing climate and biodiversity in the Holocene. The start of the epoch, in southern Europe, was characterised by a wet climate. The late Holocene, dominated by the presence of humans, is thought to have been warmer and drier. But disentangling the signature of naturally induced change vs. anthropogenically induced change continues to be difficult.

Queue the Maltese archipelago.

A small archipelago in the middle of the Mediterranean Sea

Located in the centre of the Mediterranean basin, approximately 96 km south of Sicily, Malta and a cluster of low-lying islands, including Gozo and Comino, are the focus of a recently published study in the open access journal Climate of the Past.

Study area. (a) Mediterranean region highlighting the Maltese Islands. Selected regional sites mentioned in text: 1: Lago Preola, 2: Gorgo Basso, 3: Biviere di Gela, 4: Lago Pergusa, 5: Lago Trifoglietti, 6: Lago Accesa, 7: Lago Ledro, 8: Tenaghi P., 9: SL152, 10: MNB-3, 11: NS14, 12: HCM2-22, 13: Soreq Cave; base map source: Arizona Geographic Alliance; (b) Maltese Islands: key sites mentioned in text; (c) average annual temperature and rainfall, based on Galdies (2011) data for the 30-year climatic period 1961–1990; (d) the topography and catchment area (blue) of Burmarrad.

Study area. (a) Mediterranean region highlighting the Maltese Islands. (Selected regional sites mentioned in text of the paper, but not mentioned in this blog post). (b) Maltese Islands. (Key sites mentioned in text of the paper, but not mentioned in this blog post). (c) average annual temperature and rainfall, based on Galdies (2011) data for the 30-year climatic period 1961–1990; (d) the topography and catchment area (blue) of Burmarrad. From B. Gambin et al. (2016). Click to enlarge.

It is their central Mediterranean location that makes the collection of isles so attractive, as they provide a good representation of the overall Mediterranean climate and can help decipher some of the questions regarding southern European climate during the Holocene.

The first human occupants sailed the short distance from Sicily, to settle in the region some 7200 years ago, introducing with them vegetation changes to the area. This well-defined date can be used as a possible marker to distinguish between naturally induced vegetation changes, brought about by climate variations, versus those triggered by the presence of humans.

In the paper, the researchers, led by B. Gambin, also present the first palaeoclimatic reconstruction for the Maltese islands and an updated palaeovegetation reconstruction.

But as encouraging as it sounds, using the Maltese archipelago as a study site for palaeoclimatic reconstructions has one, rather large, limitation. It has no peat bogs or lake deposits, which are the most suitable sites for the collection of data on old vegetation.

Using pollen to reconstruct the story of past climate

The spring and summer months are synonym of the onset of hay fever season for many. But the allergy triggering grains also play a surprisingly important role when it comes to reconstructing past climates, especially when there are no lakes or peat bogs around!

Palynology, the study of pollen grains, has been an important element in piecing together the history of our planet’s past climates since the early 20th Century.

Ancient pollen grains, extracted from sedimentary cores, can contribute to identifying changes in vegetation over time for a given region. If an area’s plant life changes to include more drought resistant varieties, it can point towards a warming climate in that region, whereas propagation of water-loving species might indicate wetter climes. Similarly, a sudden increase (or change) in the presence of pollen from cultivated taxa, like wheat, barely, olives, grapes, etc… highlights the presence of human (anthropogenic) influences in the region.

It is the pollen record, extracted from a core drilled in the region of Burmarrad in Northwest Malta, that the team of scientists used to compile their Maltese palaeoclimatic reconstruction.

Mediterranean climate and key events throughout the late Holocene

BM2 sedimentary profile and age–depth model interpo- lated curve. Dates on the core obtained via radiocarbon dating (for method and age detials, please see the paper). From B. Gambin et al. (2016).

BM2 sedimentary profile and age–depth model interpolated curve. Dates on the core obtained via radiocarbon dating (for method and age detials, please see the paper). From B. Gambin et al. (2016). Click to enlarge.

The 10m long BM2 drill core, extracted using a percussion corer, contained information on the climate, vegetation and precipitation history of the Maltese islands from the early Neolithic period (7280 before present,(BP)) through to the Roman age (1730 BP).

The early Neolothic

Pollen samples collected from the oldest section of the core indicate that from 7280 BP through to 6700 BP the Burmarrad region surrounded an ancient bay (in contrast to the present day agricultural plain setting) with the local vegetation affirming this. The researchers found pollen from non-arboreal (such as herbs and shrubs) taxa, as well as pollen from aquatic and marine species, such as Botryococcus, a common green algae species.

Drill core analysis also highlighted that average temperatures during this period were mild, stable and comparable to present-day values; while winter and summer precipitation levels were relatively high.

The early Neolithic period on the island coincided with the arrival of permanent settlers. But many of the pollen species which usually indicate the onset of anthropogenic influences are also native to Malta making it difficult for the scientists to draw conclusions as to whether the vegetation records show the arrival of the first human inhabitants.

A moister climate from 6700 BP resulted in the spread of Pistacia, a leafy green shrub, across the ancient bay. The damper conditions prevailed across the southern Mediterranean, with increased Pistacia populations found in Sicily and Spain too. The geographically wide-spread nature of the vegetation change indicates it was likely climate driven.

Templar period

By 6050 BP, human settlers started to make their presence felt on the tiny island. Communities started building free-standing stone temples, used for ritual purposes, which are unique to Malta. This settling period is accompanied by the rise in pollen from Olea plants – otherwise known as olive trees – herbaceous taxa such as Brassicaceae (which include mustard plants, radishes and cabbages), and fungus spores which occur in the dung of domestic livestock as well as wild herbivores.

Ggantija Temples of Malta. Image by Daniel Hausner. Attribution to Norum [GFDL ( or CC-BY-SA-3.0 (], via Wikimedia Commons

Ggantija Temples of Malta. Image by Daniel Hausner. Attribution to Norum [GFDL or CC-BY-SA-3.0], via Wikimedia Commons.

While individually these plants do not directly indicate vegetation change brought about by humans, when found together they do suggest human activity in the region, particularly the onset of grazing livestock.

The Bronze Age

The onset of the Bronze Age (4900 to 2650 BP) was marked by a drier climate where winter precipitation decreased and annual temperatures fluctuated between lows of 7°C and highs of 14°C. This coincides with the decrease in abundance of tree pollen found in the BM2 core and an increase in herbaceous taxa (plants which don’t have permanent woody stems).

Microcharcoal horizons become more prevalent in the core too, indicating an increase in fire activity. The drier climate and subsequent vegetation change might be a contributing factor to the increased burning in the region, but it is also likely that slash-and-burn farming was taking hold at this time. Further human activity is indicated by the rise in pollen from plants associated with pastoral activity and the increase in fungus spores commonly found in the dung of livestock.

The strain put on the environment of the Burmarrad Bay at this time is evident by the rise of algal spores and the Glomus fungus, typically associated with increased soil erosion rates. It is further supported by a reduction in overall pollen count in the core, indicating the land could support less plant-life.

The increased erosion rates had a significant impact on the landscape, with the marine lagoon slowly infilling with sediment and eventually becoming landlocked throughout the Bronze Age.

Roman occupation period

By 1972 BP the area became a well-developed fertile deltaic plain, so it’s not surprising that an increase in pollen concentrations from cultivated crop taxa, pointing towards a rise in agricultural activity, were found in the core. The area also benefited from a long period of stable climate with limited temperature and precipitation changes.

During this time, Malta became an important producer and exporter of olive oil, as evidenced by the extensive port-like remains, of this age, found across the island. This is supported by the Olea pollen count in the core, which is high too.

Synthesis of cultural phases, LPAZs (local pollen assemblage zones), sediment, vegetation dynamics, and climatic reconstruction: BM2 core, Malta. From B. Gambin et al. (2016).

Synthesis of cultural phases, LPAZs (local pollen assemblage zones), sediment, vegetation dynamics, and climatic reconstruction: BM2 core, Malta. From B. Gambin et al. (2016). Click to enlarge.

Climate- vs. human –driven environmental change in the Holocene

The research shows just how powerful palynology is as a tool for reconstructing past climates. The study of the BM2 core allowed scientists to put together a 7300 year history of climatic, vegetation and anthropogenic change in Malta.

At the same time it highlights the ongoing challenge of unravelling the signature of climate- vs. human –driven environmental change in the Holocene.

Taken as a whole, the researchers hope that the findings can be a starting point for further research into this subject, with hopes to gain better understanding of the factors and processes affecting past, present and future Mediterranean landscapes.

By Laura Roberts Artal, EGU Communications Officer


Gambin, B., Andrieu-Ponel, V., Médail, F., Marriner, N., Peyron, O., Montade, V., Gambin, T., Morhange, C., Belkacem, D., and Djamali, M.: 7300 years of vegetation history and climate for NW Malta: a Holocene perspective, Clim. Past, 12, 273-297, doi:10.5194/cp-12-273-2016, 2016.

Livers, guts and gills: understanding how organisms become fossils

Livers, guts and gills: understanding how organisms become fossils

It’s 10am and Thomas Clements, a 3rd year palaeobiology PhD Student, is getting ready to check on his latest experiment. Full kited up in what can only be described as a space suit, Thomas carefully approaches the fume cupboard home to his latest specimen: a decaying seabass, balanced on a specially designed ‘hammock’ in a tank of salty water. Opening the lid to check on the rotting fish, Thomas is hit by the smell, so atrocious the fume hood and protective overalls only go some way toward shielding his sense of smell. It might be a bleak start to the day, but it is central to Thomas’ research.

While the fossil record is dominated by the hard mineralised parts of organisms such as shells, teeth and bones, in the past few years palaentologists have started to rely on different fossilised remains and techniques to discover more about extinct animals.

“In fact, soft-bodied fossils are much more informative about the anatomy, physiology, ecology and behaviour of ancient organisms. They also give scientists a much better idea as to the type of conditions, ecosystems and environments in which the organisms lived,” explains Thomas.

However, before the vital clues held in the remains of soft-bodied fossils can be accurately interpreted by researchers, the processes which cause them to be preserved in the first instance must be fully understood too. This is where Thomas’s smelly study of decaying fish carcases comes in. Using seabass, because its genealogy can be traced back in time (organisms related to the blue fish are known to exist in the ancient fossil record), Thomas aims to better understand how decay processes affect the fossilisation potential of soft-tissues – especially of internal anatomy.

Thomas injects the silica gel around the probes to make sure the incisions are sealed. You can see the fish in it’s hammock. (Credit: Thomas Clemens)

Thomas injects the silica gel around the probes to make sure the incisions are sealed. You can see the fish in it’s hammock. (Credit: Thomas Clemens)

Along with the Palaeobiology Lab Group at Leicester University, Thomas has devised a series of novel experiments to investigate the process. Because he is particularly interested in how internal organs decay, Thomas cuts millimetre sized incisions into the fish, sourced from a local fishmongers, to place probes into liver, guts, stomach and even kidneys. The chemical data measured by the probes allows him to unravel both the timing and sequence of anatomical decay of the different organs.

“One of the most important parts of the experiment is to accurately recreate the natural death of the animal,” describes Thomas.

That is why it is vitally important that the wounds caused by the incisions are fully sealed with inert silica gel so as not to speed up the decay process. This also means that before any experiment, he painstakingly practices cutting and sealing for hours. By the end of his practice runs he is intimately familiar with the exact location of each internal organ and able to perform only the smallest cuts required to insert his probes.

Recreating the conditions under which an ancient fish would decay is also important. Surgical incision complete, probes inserted ready to acquire data, the fish is gently placed on a hammock of inert plastic netting (again, so that no chemicals plastic may give off will interfere with the natural break down of the body parts) and lowered into an aquarium of salty water.

Thomas’ experiments are sustainable and environmentally friendly too! Rather than placing the hammock directly on the tank floor, it is suspended in the water, by way of plastic ropes attached to the corners of the aquarium. This means that as the fish is left to decompose over time, most fish parts sink towards the base of the tank an eventually dissolve in the water – making it extremely foul-smelling, as you might imagine! Once the experiment is complete, whatever fish parts may remain on the hammock can be simply discarded and the (washed) plastic used in a new experiment.

Thomas teaches visiting PhD student, Yujing Li, about the anatomy of a Seabass. (Credit: Thomas Clemens)

Thomas teaches visiting PhD student, Yujing Li, about the anatomy of a Seabass. (Credit: Thomas Clemens)

The experiments performed so far show that the decay process is actually very quick. After 60 days, the majority of the fish has fully decomposed, with only fins and very small tissue parts remaining. It takes no more than 20 days for muscle fibres to disappear and as little as five days for ultra-structures to break down. Through his work, Thomas now knows that the preservation of soft tissues during fossilisation has to happen very quickly or conditions have to be just right.

Thomas thinks that “slowing down the decay process is what gives soft-bodied parts a better chance of preservation.”

This is why during the experiments he has been testing how changes in the conditions, from lowering the water temperature, reducing agitation of the tank, changing salinity or even reducing bioturbation (the disturbance of sediment caused by sea floor dwelling critters),  affect how likely it is for tissues to be preserved.

Despite the advances and better understanding gained through the experiments, enigmatic questions still remain: why are some organs, such as guts, often found preserved in the fossil record, but why are others, such as eyes, so much rarer? And so, Thomas’ work in the lab, complete with rotting fish, surgical gloves, spacesuit-like protective equipment and stomach turning smells continues.

By Laura Roberts Artal, EGU Communications Officer

Thomas Clements presented his work at the 2016 EGU General Assembly, at a press conference entitled: How ancient organisms moved and fed: finding out more from fossils. The full press conference can be streamed here. In addition, the work was presented in session SSP4.2: Experimental solutions to deep time problems in palaeontology. Thomas’ abstract can be found here.

Geo Talk: One of the youngest EGU 2016 General Assembly delegates sends sensor to space

Geo Talk: One of the youngest EGU 2016 General Assembly delegates sends sensor to space

Presenting at an international conference is daunting, even for the most seasoned of scientists; not so for Thomas Maier (a second year university student) who took his research (co-authored by  Lukas Kamm, a high-school student) to the EGU 2016 General Assembly! Not only was their work on developing a moisture sensor impressive, so was Thomas’ enthusiasm and confidence when presenting his research. Hazel Gibson and Kai Boggild, EGU Press Assistants at the conference, caught up with the budding researcher to learn more about the pair’s work. Scroll down to the end of this post for a full video interview with Thomas. 

Thomas Maier might seem like your average bright and enthusiastic EGU delegate, but together with his co-author Lukas Kamm, he has invented a water sensor that very well might help change the way astronauts live in space. Not only is their invention helping to revolutionise aerospace, but they are also the youngest delegates at the conference, Thomas is a second year university student at Friedrich-Alexander Universität Erlangen-Nürnberg and Lukas is attending high school at Werner-von-Siemens Gymnasium. We caught up with Thomas to speak with him about his invention.

Could you explain to us what led you to develop this water sensor?

We started this project four years ago for a contest called Jugend Forscht, a German youth sciences competition in Germany and the project we came up with was about giving plants demand driven watering. After we built our first sensor, we continued our work until it was possible to send the sensor into space, for a project called EU:CROPIS.

Can you tell us how your sensor works?

The sensor is based on a capacitive measuring method. So, you have two electrodes close to each other, which have an electrical capacitance (or ability to store an electrical charge) between them. The change in water content close to the electrodes changes the capacity of the sensor. Then we measure the capacity of the electrodes by measuring the time constant of the capacitor over time.

The greenhouse which forms part of the EU:CROPIS project. The greenhouse is home to Thomas and Lukas' water sensor. (Credit: Kai Boggild/EGU)

The greenhouse which forms part of the EU:CROPIS project. The greenhouse is home to Thomas and Lukas’ water sensor. (Credit: Kai Boggild/EGU)

Can you tell us more about the EU:CROPIS project?

The EU:CROPIS is mainly about this here [indicates greenhouse model], and this is a greenhouse which will go into space, July next year. The greenhouse will rotate and will generate different gravitational forces that may impact the amount of water available to plants which will be grown in here. And now, after a lot of work, our sensor will be placed on the very right [hand side] of the greenhouse and will measure the soil moisture for the plants.

What are you plans for this project into the future?

Our plans for the future are in taking part in the EDEN-ISS project, this is a project on the International Space Station, that is looking into planting 20 square meters of plants in the ISS and our sensor would be used too. So that is the next aim of this project.

Thanks Thomas for showing us your invention, and good luck to Lukas, who couldn’t attend the conference this year as he is busy with his high-school exams!

Interview by Hazel Gibson, video interview by Kai Boggild, EGU Press Assistants


Imaggeo on Mondays: Earth Wave

Imaggeo on Mondays: Earth Wave

Take a stroll along the norther beaches of the French Channel Coast, some kilometers east from the entrance of the Channel Tunnel, and you’ll encounter an imposing cliff of soft, sandy composition which dominates the landscape.

On close inspection, the sediments which make up the Quaternary aged deposits of the Sangatte Cliff, are beautiful, revealing intricate patterns which hold the key to the geological processes that formed them. Even at present, the landscape is being continuously shaped by marine processes which continuously erode the Quaternary soft deposits – especially during storms coupled with high tide events.

The Sangatte sedimentary sequence outcrops along a stretch of about 1.5 km along the French coast. Today’s featured image was taken by Pierre Antoine, at the base of the Quaternary sequence of the Sangatt Cliff. It corresponds to an observation window of about 80 cm large.

“At this location, explains Pierre, the Quaternary record is composed of raised beach deposits (flint pebble bar and sandy beach deposits, ± 3m thick) dating from a Middle Pleistocene interglacial (± 300 ka) and to a high sea level (± 5 m above the present day level), covered by a thick succession of chalky periglacial slope deposits, formed during periods of repeated freezing and thawing, associated with loesses and fossil soils know as palaeosols (8 to 12m).”

The greenish sandy deposits exposed at the base of the photo represent the top of the ancient marine beach deposits. These were overlain by a thin, dark bown, peat layer indicative of a phase of sea level drop. It is likely that during this time a peat bog, which was isolated from the sea by wind-driven sand dunes, developed .

This peat layer has, more recently, been strongly compressed and reworked during the deposition of the overlying thick bed of dense chalk mud. The greyish muds are the result of the weathering of the massive chalky slopes of the Sangatte Cliff,  which occurred following a cold period after the sea-level decrease. The delicate rusty bands seen in the otherwise creamy chalky muds, are the result of infiltration of iron oxide minerals throughout the cliff.


Antoine, P. 1989. Stratigraphie des formations pléistocènes de Sangatte (Pas-de-Calais), d’après les premiers travaux du Tunnel sous la Manche. Bulletin de l’Association Française pour l’Etude du Quaternaire, 37, 5-17.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at


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