Determining the time of year when the Chicxulub Impactor fell.

The end-Cretaceous extinction event wiped out 76% of known species on Earth, but was strangely selective in the way it did so. The non-Avian Dinosaurs were wiped out, as were the Pterosaurs, most Marine Reptiles, Ammonites, Belemnites, and Rudists, amongst other groups. The extinction event is believed to have been caused by a bolide impacting the Gulf of Mexico near the Yucatan Peninsula, creating the Chicxulub Impact Crater. Evidence of the direct effects of this impact, including impact glass fallout, large-scale forest fires and tsunamis, have been found in areas of North America more than 3500 km from the impact site, and the subsequent events are thought to have included a global climatic breakdown which lasted for thousands of years.

The Tanis Event Deposits of North Dakota record a seiche event (tsunami-like wave within an enclosed environment such as a river valley or small lake) including a significant death assemblage of latest Cretaceous fauna, directly overlying the End Cretaceous Hell Creek Formation. This is thought to represent the very end of the Cretaceous, containing the fossils of organisms that died and to have been burried more-or-less instantly in a seiche event brought about by that impact. The reconstruction scenario is that within a few tens of minutes of the impact, a large volume of water and soil was forced upstream from the Tanis Estuary, pushing with it large volumes of marine, freshwater, and terrestrial organisms, whilst also accumulating impact spherules (spherical silica particles formed as melted droplets of rock recrystalise in mid air) which were falling from above. Within this deposit were large numbers of Acipenseriform Fish (Sturgeon and Paddlefish), which were buried alive in alignment with the flow of the seiche, and which had numerous impact spherules trapped within their gills.

In a paper published in the journal Nature on 23 February 2022, Melanie During of the Department of Earth Sciences at the Vrije Universiteit Amsterdam, and the Subdepartment of Evolution and Development at Uppsala University, Jan Smit, also of the Department of Earth Sciences at the Vrije Universiteit Amsterdam, Dennis Voeten, also of the Subdepartment of Evolution and Development at Uppsala University, and of the European Synchrotron Radiation Facility, Camille Berruyer and Paul Tafforeau, also of the European Synchrotron Radiation Facility, Sophie Sanchez, again of the Subdepartment of Evolution and Development at Uppsala University, and the European Synchrotron Radiation Facility, Koen Stein of the Directorate ‘Earth and History of Life’ at the Royal Belgian Institute of Natural Sciences, and of Earth System Science at the Vrije Universiteit Brussel, Suzan Verdegaal-Warmerdam, again of the Department of Earth Sciences at the Vrije Universiteit Amsterdam, and Jeroen van der Lubbe, once again of the Department of Earth Sciences at the Vrije Universiteit Amsterdam, and of the School of Earth and Environmental Sciences at Cardiff University, attempt to determine the season in which the Fish of the Tanis Event Deposits died by examining cyclical bone growth patterns in their skeletons to see at which point growth ceased.

 

Reconstruction of a Paddlefish with impact spherules in the gill rakers. (a) Three-dimensional rendering of Paddlefish FAU.DGS.ND.161.4559.T in left lateral view with the location of a higher-resolution scan (depicted in (b)) indicated (white outline). (b) Three-dimensional rendering of the subopercular and gills in a with trapped impact spherules (yellow). Scale bars are 2 cm. During et al. (2022).

Tree-ring evidence of the Maastrichtian (latest Cretaceous, 72.1 to 66 million years ago) climate of North Dakota suggests a temperate climate with four distinct seasons. The Tanis site is reconstructed as having had annual temperature fluctuations that varied from an average of roughly 19 °C in summer, down to a winter average of 4–6 °C. As well as the rings in trees, these climate variations are recorded in the bones of Acipenseriform Fish, potentially providning a clock which could have recorded the season in which the Chicxulub Impactor fell. To this ende During et al. analysed three Paddlefish dentaries and three Sturgeon pectoral fin spines from the Tanis deposits.

 

PPC- SRμCT data of FAU.DGS.ND.161.4559.T, a partial Paddlefish from the Tanis locality. (a) Orthogonal virtual thin sections (100 μm thick, average-value projections) obtained in front, top, and right view. (b) Impact spherules in virtual thin sections of (a), indicated with yellow circles. Scale bars (a) 1 mm. (c) Three-dimensional rendering (in left lateral view) with virtual cross sections of (d) (blue), (e) (green), and (f) (red) indicated. (d) Coronal virtual slice. (e) Sagittal virtual slice. (f) Axial virtual slice, brain-enveloping tissues indicated with red arrows. (g) Three-dimensional rendering in right lateral view with anatomical labels. (h) Three-dimensional rendering in left lateral view with anatomical labels. During et al. (2022).

During et al. traced lines of arrested growth (marks left in growing bone by slowed growth at one time of year, typically winter in a temperate climate) in dermal bones from six Acipenseriform Fish, by preparing slices of bone as microscope slides. They corroborated this by creating a three-dimensional map of the skulls using propagation phase-contrast synchrotron radiation micro-computed tomography at the European Synchrotron Radiation Facility, which enabled optimal projection of the bone deposition pattern across multiple cross-sectional planes, enabling them to determine the relationship between growth lines and seasonality across a wider area of bone. In addition, During et al. carried out an investigation into the isotopic composition of the growth lines in one Paddlefish specimen.

 

Osteohistological thin sections of five Acipenseriform Fish. (a)–(e) Thin sections in transmitted light of VUA.GG.2017.MDX-3 (a), VUA. GG.2017.X-2743M (b), VUA.GG.2017.X-2744M (c), VUA.GG.2017.X-2733A (d) and VUA.GG.2017.X-2733B (e), showing congruent pacing of bone apposition during the final years of life, terminating in spring. Red arrows indicate lines of arrested growth. Scale bars are 0.5 mm. During et al. (2022).

The tomographic reconstructions also demonstrate that impact spherules are found only in the gill rakers of the Fish, and are absent elsewhere within their bodies, strongly supporting the idea that they were taken in during the last minutes of their lives, and did not have time to penetrate the oral cavity or further down the digestive tract before they died. This also rules out the possibility that they were introduced to the Fish post-mortem, by penetrating decomposing bodies, indicating the Fish were buried rapidly after their death, which strongly supports the idea that the death of the Fish was close to simultaneous with the arrival of the seiche wave, and therefore that these Fish were alive and active in the very last moments of the Cretaceous.

 

Carbon isotope record alongside the incremental growth profiles. (a) Proportion of carbon¹³ expressed as ‰ on the Vienna Pee Dee Belemnite reference scale. The colour gradient highlights the theoretical range between maximum values during seasonal (summer) trophic increase of carbon¹³ (yellow) and minimum values during trophic decrease of carbon¹³ (winter) (blue). (b) Virtual thick section (average-value projection with 0.1 mm depth) showing growth zones during the favourable growth seasons and annuli and lines of arrested growth outside the favourable growth seasons. (c) Cell density map of a virtual thick section (minimum-value projection with 0.2 mm depth) showing fluctuating osteocyte lacunar densities and sizes, with higher densities and largest sizes recorded during the favourable growth seasons (orange) and lower densities and smaller sizes outside the favourable growth seasons (purple). (d) Microscopic thin section in transmitted light showing lines of arrested growth (red arrows) and a single growth mark indicated (bracket) spanning the distance between two subsequent lines of arrested growth and including a zone and an annulus, Scanning data visualized in (b) and (c) were obtained approximately 10 mm distal from the physically sectioned thin slice of (d), which itself was located directly proximal to the thick section sampled for (a). Scale bars are 1 mm. During et al. (2022).

During et al. used micro-X-ray fluorescence to search for signs of taphonomic alteration within the bones, finding that iron and manganese oxides were present both within the surrounding sediments and the sediments surrounding the bones, and the vascular canals within the bones, but had not penetrated into the bone tissue itself. Potassium and silicon were present in the sediment but not in the bones, while the bones themselves maintained a homogeneous distribution of phosphorus and calcium, which would be expected in unaltered bone. The fine detail of the fossils, including the preservation of non-ossified tissues that surrounded the brains of the Fish, also points towards there being almost no taphonomic alteration of the specimens.

 

Elemental distribution maps of Acipenseriform elements from the Tanis locality obtained with micro-X-ray fluorescence. (a) Calcium, phosphorus, and manganese distribution in Paddlefish dentary VUA.GG.2017.X-2724. (b) Calcium, phosphorus, and manganese distribution in Sturgeon pectoral fin spine VUA.GG.2017.MDX-3. (c) Calcium, phosphorus, and manganese distribution in Paddlefish dentaries VUA.GG.2017.X-2733A, VUA.GG.2017.X-2733B, and the surrounding sediment matrix. (d) Calcium, phosphorus, and manganese distribution in Sturgeon pectoral fin spine VUA.GG.2017.X-2743M. (e) Calcium, phosphorus, and manganese distribution in Sturgeon pectoral fin spine VUA.GG.2017.X-2744M. (f) Potassium, silicon, and iron distribution in Paddlefish dentary VUA.GG.2017.X-2724. (g) Potassium, silicon, and iron distribution in Sturgeon pectoral fin spine VUA.GG.2017.MDX-3. (h) Potassium, silicon, and iron distribution in Paddlefish dentaries VUA.GG.2017.X-2733A, VUA. GG.2017.X-2733B and the surrounding sediment matrix. (i) Potassium, silicon, and iron distribution in Sturgeon pectoral fin spine VUA.GG.2017.X-2743M. (j) Potassium, silicon, and iron distribution in Sturgeon pectoral fin spine VUA.GG.2017.X-2744M. During et al. (2022).

The dentaries of Paddlefish form by the ossification of tissue around the Meckel’s cartilage, while the pectoral spines of Sturgeon form by the ossification of embryonic mesoderm tissue within the skin. Neither of them form by the direct ossification of cartilage. Instead they grow incrementally, with new bone tissue being secreted by rows of osteoblasts on the growing surface. This generates an annual growth pattern, with each year represented by a thick zone of bone laid down under favourable conditions, followed by a narrower area of bone laid down under less favourable growth conditions, then a line of arrested growth, representing a period when no bone was laid down. During et al.'s examination of Acipenseriform Fish remains from the terminal Cretaceous Tanis Event Deposits showed that in all cases growth had stopped for the final time shortly after the bones had begun to grow again following a line of arrested growth.

 

Osteohistology of Acipenseriform Fish from the Tanis locality. (a) Thin section of Paddlefish dentary VUA.GG.2017.X-2724 under transmitted light. (b) Detail of VUA.GG.2017.X-2724 thin section (white box in (a)), scale bar 100 μm. (c_ Detail of VUA.GG.2017.X-2724 thin section (white box in (b)), scale bar 100 μm. (d) Thin section of Sturgeon pectoral fin spine VUA.GG.2017. MDX-3 under transmitted light. (e) Detail of VUA.GG.2017.MDX-3 thin section (white box in (d)), scale bar 100 μm. (f) Detail of VUA.GG.2017.MDX-3 thin section (white box in (e)), scale bar 100 μm. (g) Thin section of Paddlefish dentary VUA. GG.2017.X-2733A under transmitted light. (h) Detail of VUA.GG.2017.X-2733A thin section (white box in (g)) with red arrows indicating lines of arrested growth, scale bar 100 μm. (i) Detail of VUA.GG.2017.X-2724 thin section (white box in (h)), scale bar 100 μm. During et al. (2022).

The visible growth lines within the bones were corroborated using stable isotope ratios, which showed seasonal variations in the proportion of carbon¹³, which is linked to diet, and a constant proportion of oxygen¹⁸, which is related to environment, and therefore indicates that the Fish had been living within the river basin their entire lives, rather than migrating to the sea (as some modern do, and which is likely to have been done by some of their Mesozoic forebears). This confirms that the the variation in carbon isotope values and growth rates reflect seasonal variations within that river basin, and not migratory behaviour on behalf of the Fish. This can be seen in both Paddlefish and Sturgeon, despite the different lifestyles of the two types of Fish.

The Paddlefish of the Late Cretaceous Tanis River Basin were filter-feeders (as are Paddlefish today), which are thought to have fed on zooplankton such as Copepods. Such a feeding strategy would have led to seasonal variations in the availability of food, with the maximum availability falling in the summer. This would have led to a summer season when the Fish was both growing faster, and absorbing a higher proportion of carbon¹³. Examination of the distribution of carbon¹³ within fossil Paddlefish bones from the Tanis deposits reveals that at the time of their deaths the proportion of carbon¹³ in their diets was rising, but had not reached its annual peak, supporting the hypothesis that when the Fish died it was spring in the northern hemisphere.

 

Previous studies on palaeobotanical material from Wyoming has suggested that the Chicxulub Impactor fell in June, although those studies are now considered unreliable for a variety of reasons, leaving us with no standing theory on the time of year when the impact event happened. During et al.'s study appears to show a direct record of the season in which Fish that died directly as a result of the impact died, giving a strong line of support for a springtime extinction event.

If correct, the finding that the Chicxulub Impactor fell in the Northern Hemisphere's spring season may go some way to explaining the selective nature of the extinction it caused. Spring is the breeding season for many Animals, which can potentially make them more vulnerable to environmental perturbations. In the aftermath of the impact the ecosystems of the Southern Hemisphere are known to have recovered much more quickly than those of the north, which could potentially have been linked to an event which hit Northern Hemisphere organisms in their breeding season. The event also impacted larger organisms, with longer breeding cycles, more than it did smaller ones with shorter breeding cycles, which could again be linked to the disruption of a breeding season. An event which happened shortly before the onset of winter in the Southern Hemisphere would have been favourable for the survival of organisms which hibernate in burrows (such as many small Mammals), and which might already have been entering a dormant phase when the bolide impacted, something which could potentially also apply to some Amphibians, Birds, and even Crocodilians. 

 

If this is the case then it goes some way towards decoupling the short- and long-term effects of the Chicxulub Impact, with the initial events being particularly harsh on organisms with a spring breeding cycle in the Northern Hemisphere, and relatively benign to organisms with a winter dormant phase in the Southern Hemisphere, while the longer term climatic and ecosystem breakdowns would favour organisms flexible in their environmental and dietary needs, which would be better able to survive amid collapsing food webs, in either hemisphere.

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Online courses in Palaeontology. 

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Leak from Keystone Pipeline causes major pollution incident in North Dakota.

A leak from the Keystone Pipeline has led to about 1.4 million litres of crude oil being released into wetlands in Walsh County, North Dakota. The leak was discovered on Tuesday 29 October 2019, causing pipeline owners TC Energy to shut down that portion of the pipeline while maintenance work is carried out. The leak presents no immediate threat to Human health, according to the North Dakota Department of Environmental Quality, as the wetlands where the spill occurred are not used as a source of water for Human consumption, but the impact of the spill on local wildlife is likely to be severe and potentially long lasting.

Oil spill in Walsh County, North Dakota, from a leak on the Keystone Pipeline in October 2019. Taylor DeVries/North Dakota Department of Environmental Quality/AP.

Oil spills are potentially harmful to aquatic life in a variety of ways. Most obviously it can coat the outside of organisms, causing damage to external structures such as the feathers of Birds and fur of Mammals, as well as smothering many aquatic invertebrates and plants. It also contains a variety of chemicals which can be directly toxic upset the hormonal balance of many animals. Oil also impedes the feeding of aquatic organisms, coating both food and feeding organs, but provides an excellent food source for Bacteria, which can lead to Eutrophication events - dramatic increases in Bacteria numbers, which then use all the oxygen in the water, leading other organisms to asphyxiate.

The Keystone Pipeline began operation in 2010 and carries crude oil extracted from oil sands in the Western Canadian Sedimentary Basin to refineries in Illinois and Texas. The pipeline has suffered a number of similar leaks which have caused alarm among environmental groups, many of whom opposed the construction of the pipeline in the first place. The spills have also served to deepen opposition to the larger Keystone XL Pipeline, which is planned by TC Energy to run through Alberta, Montana, South Dakota and Nebraska. The Keystone XL Pipeline project was blocked by the Obama-administration in 2015 due to concerns about the environmental impact and economic viability of the project, but this block was overturned by the incoming Trump-administration in 2017, though the legality of this is still being challenged in several courts in the US.

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Didelphodon vorax: Crania of a large carnivorous Metatherian Mammal from the Late Cretaceous of Montana and North Dakota.

Placental Mammals are more abundant than Marsupials in almost all modern ecosystems; however in the Late Cretaceous the Metatherans (the wider group that includes the Marsupials - without knowledge of the reproductive system of an ancient Mammal it is impossible to say whether we would consider if a Marsupial or not, so this term is restricted to the last common ancestor of all living Marsupials and everything descended to it, while the term Metatheran is used to indicate anything more closely related to the modern Marsupials than the modern Placentals) were much more widespread and diverse, inhabiting a broad range of ecological niches, even in Northern Hemisphere regions from which they are now absent. Sixty species of Metatherans have been described from the Late Cretaceous of North America to date, although the majority of these are known only from teeth and other fragmentary remains, and intact crania (skulls) are extremely rare. Didelphodon vorax was first described in 1889 by palaeontologist Othniel Charles Marsh. It was a large Mammal by Cretaceous standards, probably reaching around 5 kg in mass, with teeth suggesting a carnivorous diet and a skeleton interpreted as implying a possible semi-aquatic lifestyle.

In a paper published in the journal Nature Communications on 8 December 2016, Gregory Wilson of the Department of Biology and Burke Museum at the University of Washington, Eric Ekdale of the Department of Biology at San Diego State University and the Department of Paleontology at the San Diego Natural History Museum, John Hoganson of the North Dakota Geological Survey, Jonathan Calede, also of the Department of Biology and Burke Museum at the University of Washington and Abby Vander Linden of the Graduate Program in Organismic and Evolutionary Biology at the University of Massachusetts describe four new specimens of Didelphodon vorax, including a nearly complete skull, two maxilae (upper jaws) and a detached snout from the Late Cretaceous Hell Creek Formation of Montana and North Dakota.

Skull of the Late Cretaceous marsupialiform Didelphodon vorax. Specimen NDGS 431, in anterior (a), left lateral (b), posterior (c), dorsal (d) and ventral (e) views, and specimen UWBM 94084, in anterior (f), left lateral (g), dorsal (h) and ventral (i) views. All images from digitally rendered, micro-CT scans. as, alisphenoid; bo, basioccipital; bs, basisphenoid; C, upper canine; I1–4, upper incisors 1–4; inp, internarial process; inf, incisive foramen; iof, infraorbital foramen; ip, interparietal; ju, jugal; M1–4, upper molars 1–4; mapf, major palatine fenestra; mp, mastoid process; mpf, minor palatine foramen; mx, maxilla; na, nasal; P1–3, upper premolars 1–3; pa, parietal; pe, petrosal; pgp, postglenoid process; pmx, premaxilla; ppt, postpalatine torus; ps, presphenoid; pt, pterygoid; rtpp, rostral tympanic process of the petrosal; so, supraoccipital; sq, squamosal. Scale bar, 10 mm. Wilson et al. (2016).

These cranial remains enable some reconstruction of the biology and ecology of Didelphodon vorax. From the anatomy of the whole cranium (which is not thought to have come from a fully mature individual) Wilson et al. estimate that the living animal has a bite force measured at the canines of 218 Newtons. This is lower than that of many living and fossil Mammals (for example the European Badger has a bite force of 244 Newtons), but, due to the small mass of Didelphodon vorax, translates into a bite force quotient (a ration of bite force to size) of 201, higher than that of any other Mammal for which this has been calculated, living or fossil; exceeding that of the Tasmanian Devil (166), Spotted Hyena (114) and African Lion (116) as well as the extinct Marsupial Lion (193) and Dire Wolf (157).

Reconstruction of the skull and jaw of Didelphodon vorax. The reconstruction is shown in anterior (a), posterior (b), dorsal (c), ventral (d), and right lateral (e) views. It is based on NDGS 431 (basicranium, palate, skull roof and dentition), UWBM 94084 (rostrum), UWBM 94500 (palate and maxillo-jugal contact), SCNHM VMMa 20 (maxillo-jugal contact) and UWBM 102139 (dentary). The areas not preserved in the actual specimens include the lower incisors, some upper incisors, parts of the orbitotemporal and occiput regions, and some sutures. Uncertainties in sutures ar represented by dashed lines. Scale bar, 10 mm. Wilson et al. (2016).

Such a bite force, combined with the dentition of Didelphodon vorax, which is typical of a carnivorous diet, would appear to suggest the species was a durophagous carnivore similar to a modern Hyena or Big Cat. However examination of the wear on the teeth of the specimens does not match that seen on such animals, rather being closer to that seen on malacavorous animals (animals that feed mainly on Molluscs). Since this diet does not match the dentition of Didelphodon vorax, Wilson et al. suggest the species may have been omnivorous in diet.

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Apartment block evacuated after fire at North Dakota oil treatment center.

An apartment block to the south of Watford City in North Dakota was temporarily evacuated following a fire at a nearby oil treatment center which broke out at about 6.30 pm local time on Saturday 14 February 2015, according to McKenzie County Emergency Management. Local fire crews were able to extinguish the fire in about half an hour, and residents were able to return to their homes later that evening. There is thought to have been no threat to human health from the incident, with the evacuations being carried out purely as a precaution.

Fire at an oil treatment center near Watford City, North Dakota, on 15 February 2015. Clayton Bjornson/KXNews.

An oil boom in North Dakota led to tens of thousands of people migrating in search of work, with many living in trailer parks, prefabricated barracks-style buildings or even sleeping in tents or cars. However the industry is becoming a cause of rising concern, and since 2010 has accounted for half of all industrial deaths in the state. 

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One dead following explosion at North Dakota oil well.

One man has died and another was injured following an explosion at a QEP Resources owned oil well near Mandaree on the Fort Berthold Reservation in North Dakota on 13 January 2015. The man who died has been named as Wes Herrman from Conyers...

Six injured as Tornado hits North Dakota oil workers camp.

Six people have been injured, one critically, after a tornado hit a campsite used by oil workers and their families...

City evacuated after train derailmet causes huge oil explosion.

The city of Casselton, North Dakota, has been evacuated after a train derailment led to a huge oil explosion on Monday 30 December 2013. The incident happened...

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One dead following explosion at North Dakota oil well.

One man has died and another was injured following an explosion at a QEP Resources owned oil well near Mandaree on the Fort Berthold Reservation in North Dakota on 13 January 2015. The man who died has been named as Wes Herrman from Conyers, Georgia, the owner of service company Legendary Field Services, and the second man is understood to be an employee of the same company. The men are understood to have been carrying out a routine operation at the time of the incident, removing a tube from the well heater, when fluid in the pipe ignited for some reason, engulfing the men in a fireball. Mr Herrman was air-lifted to the St. Paul Regional Burn Center but died the following day. The incident is being investigated by the Occupational Safety and Health Administration.

 Wes Herrman of Legendary Field Services. Grand Fork Herald.

This is the first oil industry death in North Dakota this year, the most recent incident having occurred on 18 November 2014. However the industry is becoming a cause of rising concern, and since 2010 has accounted for half of all industrial deaths in the state. An oil boom in North Dakota led to tens of thousands of people migrating in search of work, with many living in trailer parks, prefabricated barracks-style buildings or even sleeping in tents or cars.

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Six injured as Tornado hits North Dakota oil workers camp.                                                         Six people have been injured, one critically, after a tornado hit a campsite used by oil workers and their families...

City evacuated after train derailmet causes huge oil explosion.                                                   The city of Casselton, North Dakota, has been evacuated after a train derailment led to a huge oil explosion on Monday 30 December 2013. The incident happened...

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How changes in Plant ecology shed light on the End Cretaceous Extinction Event.

One of the two main theories that seeks to explain the extinction event at the end of the Cretaceous postulates that a large bolide (extra-terrestrial object such as a comet or asteroid) smashed into the Yucatan Peninsula in Mexico close to the modern town of Chicxulub, resulting in a devastating explosion and long term climate change. Such an event would have led to a ‘nuclear winter’ as large amounts of material thrown up into the atmosphere significantly reduced the amount of sunlight reaching the planets surface, leading to a breakdown in food chains and causing the mass extinction event.

Such an event would have a profound impact on plant survival strategies, as darker skies would lead to a much shorter growing season, favouring deciduous plants over evergreens. It is difficult to tell directly from the fossil record whether a plant was deciduous or evergreen in nature, though deciduous plants on the whole have lower leaf mass per area (high leaf mass requires higher carbon investment) and higher vein densities (which aids carbon assimilation), so comparison of these two measures across an ecosystem should give some indication as to whether it was dominated by deciduous or evergreen forms.

In a paper published in the journal PLoS Biology on 16 September 2014, a team of scientists led by Benjamin Blonder of the Department of Ecologyand Evolutionary Biology at the University of Arizona and the Rocky MountainBiological Laboratory in Gothic, Colorado, describe the results of an analysis of fossil leaves from the Hell Creek and Fort Union formations in southwestern North Dakota, which cover a 2.2 million year section across the Cretaceous/Palaeocene boundary (the last 1.4 million years of the Cretaceous and first 800 000 years of the Palaeocene).

Blonder et al. found that the leaf mass per area of leaves in the study dropped by an average of 6 grams of dry leaf mass per meter squared across the Cretaceous/Palaeocene boundary, while vein density rose by 1.1 mm of vein per mm² of leaf area across the boundary. These are small values across the total range of variability found in modern plants, but consistent with a change in ecosystem from (for example) tropical rainforest to tropical deciduous forest.

Visual representations of trait changes across the Cretaceous/Palaeocene Boundary. Top row, increase in vein density as seen in (A), ‘‘Dryophyllum’’subfalcatum,230.7 m stratigraphic depth, vein density = 2.5 mm^-1 and (B) unknownnonmonocot (morphospecies FU87), 1.275 m depth, VD = 5.3 mm^-1.Bottom row, decreases in leaf mass per area as seen through decreasing petiole width forsimilar leaf area in (C) ‘‘Ficus’’planicostata, 23.6 m depth, leaf mass per area = 136 g m^-2and (D) ‘‘Populus’’nebrascensis, 7.2 m depth, leaf mass per area = 48 g m^-2. Scale bars,(A and B) 500 mm and (C and D), 5 mm. Blonder et al. (2014).

These variables have been shown to change across the Cretaceous/Palaeocene boundary before, but over longer periods and over wider areas. By producing a study of a much shorter time-span over a limited area, Blonder et al. hope to provide evidence for a much faster change in ecosystem than was previously possible. They note that a drop in leaf mass per area and rise in vein density could also be caused by a drop in atmospheric carbon dioxide, which is a probable symptom of the other main theoretical cause of the End Cretaceous Extinction Event, the extensive volcanism associated with the formation of the Deccan Traps flood basalts in India. However such volcanism would be more likely to cause a long-term drop in atmospheric carbon dioxide, leading to a gradual change in leaf mass per area and vein density, where as the study supports an abrupt change in variables, harder to explain though a change in atmospheric chemistry, unless this was more sudden than could be explained by our current understanding of flood volcanism.

 

See also…

The cause of the end-Permian extinction.

The Earth has been dominated by multi-cellular life forms (animals...

The nature of the Chicxulub impactor.                                                                                  65 million years ago, at the end of the Cretaceous, the Earth underwent the last of the five great mass extinctions recorded in the fossil record. While this is by no means the largest of these events, it is the most familiar to the general public, as it was responsible for the extinction of, amongst other things, the non-Avian Dinosaurs and the large marine Reptiles of...

  

Opportunistic Bivalves during the Early Jurassic Toarcian Oceanic Anoxic Event.        The Toarcian Oceanic Anoxic Event is an extinction event that took place in the Early Jurassic, about 183 million years ago. It took place in four phases, thought to have been related to Milankovitch Cycles. During each phase the temperature of the global ocean is thought to have risen abruptly by as much as 13℃, leading to a...

 

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Six injured as Tornado hits North Dakota oil workers camp.

Six people have been injured, one critically, after a tornado hit a campsite used by oil workers and their families near Watford City in McKenzie County, North Dakota at about 7.50 pm local time on Monday 26 May 2014, destroying 15 trailers. None of the people involved has been named, but it is understood to be a 15-year-old girl, and has been flown to hospital in Minot. Tornadoes are not an uncommon occurrence in North Dakota at this time of year, and most permanent homes have good storm shelters. However an oil boom in the state has led to tens of thousands of people migrating in search of work, with many living in trailer parks, prefabricated barracks-style buildings or even sleeping in tents or cars.

Image captured as the storm approaching the McKenzie County worker's camp on Monday 26 May 2014. Associated Press.

Tornadoes are formed by winds within large thunder storms called super cells. Supercells are large masses of warm water-laden air formed by hot weather over the sea, when they encounter winds at high altitudes the air within them begins to rotate. The air pressure will drop within these zones of rotation, causing the air within them so rise, sucking the air beneath them up into the storm, this creates a zone of rotating rising air that appears to extend downwards as it grows; when it hits the ground it is called a tornado. 

The 26 May 2014 McKenzie County tornado reached two on the Enhanced Fujita scale (or an EF-2 tornado), with winds peaking at 190 km per hour.

The aftermath of the 26 May McKenzie County tornado. abc7.

Tornadoes can occur anywhere in the world, but are most common, and most severe, in the area of the American mid-west known as 'Tornado Ally', running from Texas to Minnisota, which is fueled by moist air currents from over the warm enclosed waters of the Gulf of Mexico interacting with cool fast moving jet stream winds from the Rocky Mountains. Many climatologists are concerned that rising temperatures over the Gulf of Mexico will lead to more frequent and more severe tornado events.

The approximate location of the camp hit by the 26 May 2014 McKenzie County tornado. Google Maps.

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 Missouri town hit by tornado.

Residents of the town of Orrick in Ray County, Missouri, are cleaning up after a tornado hit at about 5.30 pm on Saturday 10 May 2014. The town received about 15 minutes warning of the event...

 At least 32 dead as tornados hit Arkansas, Alabama, Iowa, Kansas, Mississippi and Oklahoma.

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At least 18 people have been injured and many more left without homes or electricity following an outbreak of tornadoes on the evening of Friday 25 April 2014. Fifteen of those known to have...

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City evacuated after train derailmet causes huge oil explosion.

The city of Casselton, North Dakota, has been evacuated after a train derailment led to a huge oil explosion on Monday 30 December 2013. The incident happened slightly after 2 pm local time (slightly after 8 pm GMT) about 8 km to the northwest of the city, when a 112 car grain train derailed, hitting an oil carrying train of 106 cars, and derailing 20 of its cars, 19 of which were carrying oil. The accident triggered a fire which engulfed about 20 of the cars. Firefighters were able to detach and remove 50 of the 104 oil bearing cars, but the fire was deemed to dangerous to approach any closer, and will be left to burn itself. The city of Casselton, population 2432, was evacuated as a precaution, due to toxic fumes from the burning train and the danger of further explosions.

The burning train near Casselton, North Dakota, on Monday 20 December 2013. Ken Pawluk/AP.

Trains carrying crude oil have become an increasingly important part of the distribution system in North America as both production of and demand for oil has exceeded the capacity of the pipeline network. There have been a number of incidents involving derailments and oil spills, and concerns about the safety of the trains following an incident in Lac-Megantic, Quebec, when a 72 car oil train derailed and exploded, killing 47 people.

See also Oil pipeline explosion kills 35 in eastern Shandong Province, China, Millipedes blamed for Australian rail crash, Drilling rig burning in southern Texas, Massive oil explosions in Quebec, Copper spill causes pollution alert on the Edith River in the Northern Territory, Australia.

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