Stratigraphy, Sedimentology and Palaeontology

Imaggeo on Mondays: The odd ‘living’ rocks

Imaggeo on Mondays: The odd ‘living’ rocks

Microbialites – structures which result from the interaction between microbes and sediments – have existed in the rock record since 3700 Ma ago until the present day. The presence of microbes in environments where mineral precipitation is prevalent, usually derives in the development of such chemical sedimentary structures. This can take place in marine, non-marine, and subterranean environments. The most common type of microbialites may be referred to as stromatolites.

The stromatolites shown here formed ~72 Ma ago in an intra-arc basin – a basin, located between two chains of volcanoes formed above subducting plates, where sediments deposit –  within the Tarahumara Formation, which was emplaced during the Laramide orogeny (some 70 to 80 million years ago) in Northwestern Mexico (Sonora).

The locality has been named the Huepac Chert because of the presence of thin and thick chert – a very fine grained rock made of silicon dioxide – horizons. The chert is black and it contains a great variety of fossils, including pollen grains, fungal spores, green algae, cyanobacteria, diatoms, arthropod remains, fruits, palm roots, aquatic plants (e.g. Haloragaceae), and numerous achritarchs.

Preliminary studies of the Fe2O3/TiO2 and MnO/TiO2 ratios in the chert suggest that hydrothermal activity was frequent and that it promoted the deposition of the majority of the chert where important organisms are beautifully preserved.  Iron-rich laminae, instraclasts, and evaporation processes may be inferred for the topmost sediments covering the stromatolites, suggesting that the water level fluctuated while these structures were forming.

There is still much work to do regarding the paleoenvironments where those Cretaceous stromatolites developed. These Upper Cretaceous successions are rare in Sonora, and biostratigraphic correlations can be made only with one locality to the South (Cerro El Obispo), but no other localities with similar lithology and fossil content have been reported.

By Hugo Beraldi, researcher at the Institute of Geology of the National Autonomous University of Mexico

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

Celebrating Earth Science Week!

Celebrating Earth Science Week!

For those not so familiar with the Earth sciences, geosciences and all its subdisciplines might be shrouded in mystery:  boring, unfathomable, out of reach and with little relevance to everyday life. Nothing could be further from the truth!

Earth Science Week, an international annual celebration founded by the American Geosciences Institute in 1998, aims to change the public’s perception of the geosciences.  Since 2011, the London Geological Society also hosts a range of events and activities to raise awareness and better understanding of the Earth sciences.

In 2016, Earth Science Week takes place between 8 and16 October. For the first time, the EGU will run events to mark the special date, all of which we invite you to take part in!

Earth Science Week Photo Competition

From Wednesday 5th to Friday 14th October submit an original photo on any broad theme related to the Earth, planetary and space sciences to our open access image repository, Imaggeo.

For your image to be included in the competition be sure to include the tag #EarthSciWeek when prompted during the upload.

Upon the submission period closing, all entered images will be published to the EGU’s Facebook page. The photograph with most likes, as chosen by the public, will be crowned the competition winner.

The winner will get one free book of their choice from the EGU library and a pack of EGU goodies! We’ll also feature the top five most popular entries on our Instagram.

I’m a geoscientist – Ask me Anything: Live Twitter Q&As

Have you always wanted to know how glaciers move and carve out unbelievable landscapes? How about which emissions cause the most pollution? What are the benefits of publishing in an open access journal vs. a pay-walled publication? If politicians make all the decisions, how can we get them to take scientists more seriously?

If you’ve ever asked yourself these questions, stay tuned or, better still, take part in our daily Earth Science Week live #EGUchat with an EGU member on Twitter. Starting on Monday, every lunchtime, you’ll have the opportunity to put your questions to a range of scientists and EGU experts and discuss a variety of subjects.

Our very own Sarah Connors (@connors SL), the EGU’s Policy Fellow, will kick off a week, of what we hope will be fruitful discussions, by taking questions on all things science policy. Come Tuesday Emma Smith (@emma_c_smith) and Nanna Karlsson (@icymatters), Cryosphere Division Blog editors, will team up to shed light on the processes which operate in the iciest places on the planet.

Wednesday brings editor of the EGU’s open access journal Earth Surface Dynamics (ESurf) and Professor of Physical Geography at the University of Hull, Tom Coulthard (@Tom_Coulthard), who will shed light on the processes which shape our planet and the trials and tribulations of getting published.

If you are interested in natural hazards, how we mitigate, manage them and how they impact on our daily lives, then tune in to the chat on Thursday, where Giorgio Boni (@EguNHpresident), President of the Natural Hazards Division will be answering all your questions!

For the final chat of the week, we bring you Michelle Cain (@civiltalker), an atmospheric scientist and former Atmospheric Division Early Career Scientist Representative. Michelle will be taking questions on gaseous emissions and topics related to the Earth’s atmosphere.

Joining the conversation couldn’t be easier! To put your questions to our experts follow the hashtag #EGUchat on Twitter. Not on twitter or aren’t available during the chats? Not to worry, send us your questions in the comments below or via Twitter, Facebook or Instagram: we’ll ask the experts on your behalf.earth_sci_week_ama_twitter-01


Imaggeo on Mondays: The road to nowhere – natural hazards in the Peloponnese

Imaggeo on Mondays: The road to nowhere – natural hazards in the Peloponnese

The Gulf of Corinth, in southern Greece, separates the Peloponnese peninsula from the continental mainland. The structural geology of the region is complex, largely defined by the subduction of the African Plate below the Eurasian Plate (a little to the south).

The Gulf itself is an active extensional marine basin, i.e., one that is pulling open and where sediments accumulate. Sedimentary basins result from the thinning, and therefore sinking, of the underlying crust (though other factors can also come into play). The rifting in the region is relatively new, dating back some five million years, and results in rare but dangerous earthquakes.

The active tectonics result in a plethora of other natural hazards, not only earthquakes.  Minor and major faults crisscross the area and have the potential to trigger landslides, posing a threat to lives and infrastructure. A road, swept away in a landslide, in the northern Peloponnese (along the southern margin of the Corinth rift) is a clear example of the hazard.

“This photo was taken in the Valimi fault block [editor’s note: a section of bedrock bound on either side by faults], east of the Krathis valley. West of this valley, the landscape is characterised by  narrow and deep gorges as the present day rivers cut into the well-consolidated conglomerates deposited during the active extension of the basin,” explains Romain Hemelsdaël, author of this week’s imaggeo on Mondays photograph.

Characteristically, sediments deposited in actively extensional rifts where the Earth’s crust and lithosphere are being pulled apart, as at the Gulf of Corinth, change in size (both horizontally and vertically) and composition. To the east of the Krathis valley, the sediments are being uplifted and are dominated by less competent sandstones and siltstones, as opposed to the conglomerates found in the Valimi fault block.

“The present landscape along this part of the rift margin forms large valleys covered by active landslides,” clarifies Romain. “In this photograph, the road was initially constructed directly on silts which were deposited by lakes and rivers. Up the hill, a temporary track currently replaces the road but this track still remains within an active landslide.”


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

Who do you think most deserves the title of the Mother of Geology?

Who do you think most deserves the title of the Mother of Geology?

Much ink is spilled hailing the work of the early fathers of geology – and rightly so! James Hutton is the mind behind the theory of uniformitarianism, which underpins almost every aspect of geology and argues that processes operating at present operated in the same manner over geological time, while Sir Charles Lyell furthered the idea of geological time. William Smith, the coal miner and canal builder, who produced the first geological map certainly makes the cut as a key figure in the history of geological sciences, as does Alfred Wegener, whose initially contested theory of continental drift forms the basis of how we understand the Earth today.

Equally deserving of attention, but often overlooked, are the women who have made ground-breaking advances to the understanding of the Earth. But who the title of Mother of Geology should go to is up for debate, and we want your help to settle it!

In the style of our network blogger, Matt Herod, we’ve prepared a poll for you to cast your votes! We’ve picked five leading ladies of the geoscience to feature here, but they should only serve as inspiration. There are many others who have contributed significantly to advancing the study of the planet, so please add their names and why you think they are deserving of the title of Mother of Geology, in the comment section below.

We found it particularly hard to find more about women in geology in non-English speaking country, so if you know of women in France, Germany, Spain, etc. who made important contributions to the field, please let us know!

Mary Anning (1799–1847)

Credited to 'Mr. Grey' in Crispin Tickell's book 'Mary Anning of Lyme Regis' (1996).

Mary Anning. Credited to ‘Mr. Grey’ in Crispin Tickell’s book ‘Mary Anning of Lyme Regis’ (1996).

Hailing from the coastal town of Lyme Regis in the UK, Mary was born to Richard Anning, a carpenter with an interest in fossil collecting. On the family’s doorstep were the fossil-rich cliffs of the Jurassic coast. The chalky rocks provided a life-line to Mary, her brother and mother, when her father died eleven years after Mary was born. Upon his death, Richard left the family with significant debt, so Mary and her brother turned to fossil-collecting and selling to make a living.

Mary had a keen eye for anatomy and was an expert fossil collector. She and her brother are responsible for the discovery of the first Ichthyosaurs specimen, as well as the first plesiosaur.

When Mary started making her fossil discoveries in the early 1800s, geology was a burgeoning science. Her discoveries contributed to a better understanding of the evolution of life and palaeontology.

Mary’s influence is even more noteworthy given that she was living at a time when science was very much a man’s profession. Although the fossils Mary discovered where exhibited and discussed at the Geological Society of London, she wasn’t allowed to become a member of the recently formed union and she wasn’t always given full credit for her scientific discoveries.

Charlotte Murchinson (1788–1869)

Roderick and Charlotte Murchinson made a formidable team. A true champion of science, and geology in particular, Charlotte, ignited and fuelled her husband’s pursuit of a career in science after resigning his post as an Army officer.

Roderick Murchinson’s seminal work on establishing the first geologic sequence of Early Paleozoic strata would have not arisen had it not been for his wife’s encouragement. With Roderick, Charlotte travelled the length and breadth of Britain and Europe (along with notable friend Sir Charles Lylle), collecting fossils (one of the couple’s trips took them to Lyme Regis where they met and worked with Mary Anning, who later became a trusted friend) and studying the geology of the old continent.  Roderick’s first paper, presented at the Geological Society in 1825 is thought to have been co-written by Charlotte.

Not only was Charlotte a champion for the sciences, but she was a believer in gender equality. When Charles Lylle refused women to take part in his lectures at Kings Collage London, at her insistence he changed his views.

Florence Bascom (1862–1945)

By Camera Craft Studios, Minneapolis - Creator/Photographer: Camera Craft Studios, Minneapolis Medium: Black and white photographic print. Persistent Repository: Smithsonian Institution Archives Collection: Science Service Records, 1902-1965 (Record Unit 7091)

By Camera Craft Studios, Minneapolis – Creator/Photographer: Camera Craft Studios, Minneapolis. Persistent Repository: Smithsonian Institution Archives Collection: Science Service Records, 1902-1965 (Record Unit 7091)

Talk about a life of firsts: Florence Bascom, an expert in crystallography, mineralogy, and petrography, was the first woman hired by the U.S Geological Survey (back in 1896); she was the first woman to be elected to the Geological Society of America (GSA) Council (in 1924) and was the GSA’s first woman officer (she served as vice-president in 1930).

Florence’s PhD thesis (she undertook her studies at Johns Hopkins University, where she had to sit behind a screen during lectures so the male student’s wouldn’t know she was there!), was ground-breaking because she identified, for the first time, that rocks previously thought to be sediments were, in fact, metamorphosed lavas. She made important contributions to the understanding of the geology of the Appalachian Mountains and mapped swathes of the U.S.

Perhaps influenced by her experience as a woman in a male dominated world, she lectured actively and went to set-up the geology department at Bryn Mawr College, the first college where women could pursue PhDs, and which became an important 20th century training centre for female geologist.

Inge Lehmann (1888-1993)

There are few things that scream notoriety as when a coveted Google Doodle is made in your honour. It’s hardly surprising that Google made such a tribute to Inge Lehmann, on the 127th Anniversary of her birth, on 13th May 2015.

The Google Doodle celebrating Inge Lehmann's 127th birthday.

The Google Doodle celebrating Inge Lehmann’s 127th birthday.

A Danish seismologist born in 1888, Inge experienced her first earthquake as a teenager. She studied maths, physics and chemistry at Oslo and Cambridge Universities and went on to become an assistant to geodesist Niels Erik Nørlund. While installing seismological observatories across Denmark and Greenland, Inge became increasingly interested in seismology, which she largely taught herself. The data she collected allowed her to study how seismic waves travel through the Earth. Inge postulated that the Earth’s core wasn’t a single molten layer, as previously thought, but that an inner core, with properties different to the outer core, exists.

But as a talented scientist, Inge’s contribution to the geosciences doesn’t end there. Her second major discovery came in the late 1950s and is named after her: the Lehmann Discontinuity is a region in the Earth’s mantle at ca. 220 km where seismic waves travelling through the planet speed up abruptly.

Marie Tharp (1920-2006)

That the sea-floor of the Atlantic Ocean is traversed, from north to south by a spreading ridge is a well-established notion. That tectonic plates pull apart and come together along boundaries across the globe, as first suggested by Alfred Wegener, underpins our current understanding of the Earth. But prior to the 1960s and 1970s Wegener’s theory of continental drift was hotly debated and viewed with scepticism.

Bruce Heezen and Marie Tharp with the 1977 World Ocean’s Map. Credit: Marie Tharp maps, distributed via Flickr.

Bruce Heezen and Marie Tharp with the 1977 World Ocean’s Map. Credit: Marie Tharp maps, distributed via Flickr.

In the wake of the Second World War, in 1952, in the then under resourced department of Columbia University, Marie Tharp, a young scientist originally from Ypsilanti (Michigan), poured over soundings of the Atlantic Ocean. Her task was to map the depth of the ocean.

By 1977, Marie and her boss, geophysicist Bruce Heezen, had carefully mapped the topography of the ocean floor, revealing features, such as the until then unknown, Mid-Atlantic ridge, which would confirm, without a doubt, that the planet is covered by a thin (on a global scale) skin of crust which floats atop the Earth’s molten mantle.

Their map would go on to pave the way for future scientists who now knew the ocean floors weren’t vast pools of mud. Despite beginning her career at Columbia as a secretary to Bruce, Marie’s role in producing the beautiful world ocean’s map propelled her into the oceanography history books.

Over to you! Who do you think the title of the Mother of Geology should go to? We ran a twitter poll last week, asking this very question, and the title, undisputedly, went to Mary Anning. Do you agree?

By Laura Roberts, EGU Communications Officer


All references to produce this post are linked to directly from the text.

EGU, the European Geosciences Union, is Europe’s premier geosciences union, dedicated to the pursuit of excellence in the Earth, planetary, and space sciences for the benefit of humanity, worldwide. It is a non-profit international union of scientists with over 12,500 members from all over the world. Its annual General Assembly is the largest and most prominent European geosciences event, attracting over 11,000 scientists from all over the world.

This text was edited on 1 Septmember 2016 to correct the spelling of Weger. With thanks to Torbjörn Larsson for spotting the typo.



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