Tous les articles par Alain Préat

Full-time professor at the Free University of Brussels, Belgium apreat@gmail.com apreat@ulb.ac.be • Department of Earth Sciences and Environment Res. Grp. - Biogeochemistry & Modeling of the Earth System Sedimentology & Basin Analysis • Alumnus, Collège des Alumni, Académie Royale de Sciences, des Lettres et des Beaux Arts de Belgique (mars 2013). http://www.academieroyale.be/cgi?usr=2a8crwkksq&lg=fr&pag=858&rec=0&frm=0&par=aybabtu&id=4471&flux=8365323 • Prof. Invited, Université de Mons-Hainaut (2010-present-day) • Prof. Coordinator and invited to the Royal Academy of Sciences of Belgium (Belgian College) (2009- present day) • Prof. partim to the DEA (third cycle) led by the University of Lille (9 universities from 1999 to 2004) - Prof. partim at the University of Paris-Sud/Orsay, European-Socrates Agreement (1995-1998) • Prof. partim at the University of Louvain, Convention ULB-UCL (1993-2000) • Since 2015 : Member of Comité éditorial de la Revue Géologie de la France http://geolfrance.brgm.fr • Since 2014 : Regular author of texts for ‘la Revue Science et Pseudosciences’ http://www.pseudo-sciences.org/ • Many field works (several weeks to 2 months) (Meso- and Paleozoic carbonates, Paleo- to Neoproterozoic carbonates) in Europe, USA (Nevada), Papouasia (Holocene), North Africa (Algeria, Morrocco, Tunisia), West Africa (Gabon, DRC, Congo-Brazzaville, South Africa, Angola), Iraq... Recently : field works (3 to 5 weeks) Congo- Brazzaville 2012, 2015, 2016 (carbonate Neoproterozoic). Degree in geological sciences at the Free University of Brussels (ULB) in 1974, I went to Algeria for two years teaching mining geology at the University of Constantine. Back in Belgium I worked for two years as an expert for the EEC (European Commission), first on the prospecting of Pb and Zn in carbonate environments, then the uranium exploration in Belgium. Then Assistant at ULB, Department of Geology I got the degree of Doctor of Sciences (Geology) in 1985. My thesis, devoted to the study of the Devonian carbonate sedimentology of northern France and southern Belgium, comprised a significant portion of field work whose interpretation and synthesis conducted to the establishment of model of carbonate platforms and ramps with reefal constructions. I then worked for Petrofina SA and shared a little more than two years in Angola as Director of the Research Laboratory of this oil company. The lab included 22 people (micropaleontology, sedimentology, petrophysics). My main activity was to interpret facies reservoirs from drillings in the Cretaceous, sometimes in the Tertiary. I carried out many studies for oil companies operating in this country. I returned to the ULB in 1988 as First Assistant and was appointed Professor in 1990. I carried out various missions for mining companies in Belgium and oil companies abroad and continued research, particularly through projects of the Scientific Research National Funds (FNRS). My research still concerns sedimentology, geochemistry and diagenesis of carbonate rocks which leads me to travel many countries in Europe or outside Europe, North Africa, Papua New Guinea and the USA, to conduct field missions. Since the late 90's, I expanded my field of research in addressing the problem of mass extinctions of organisms from the Upper Devonian series across Euramerica (from North America to Poland) and I also specialized in microbiological and geochemical analyses of ancient carbonate series developing a sustained collaboration with biologists of my university. We are at the origin of a paleoecological model based on the presence of iron-bacterial microfossils, which led me to travel many countries in Europe and North Africa. This model accounts for the red pigmentation of many marble and ornamental stones used in the world. This research also has implications on the emergence of Life from the earliest stages of formation of Earth, as well as in the field of exobiology or extraterrestrial life ... More recently I invested in the study from the Precambrian series of Gabon and Congo. These works with colleagues from BRGM (Orléans) are as much about the academic side (consequences of the appearance of oxygen in the Paleoproterozoic and study of Neoproterozoic glaciations) that the potential applications in reservoir rocks and source rocks of oil (in collaboration with oil companies). Finally I recently established a close collaboration with the Royal Institute of Natural Sciences of Belgium to study the susceptibility magnetic signal from various European Paleozoic series. All these works allowed me to gain a thorough understanding of carbonate rocks (petrology, micropaleontology, geobiology, geochemistry, sequence stratigraphy, diagenesis) as well in Precambrian (2.2 Ga and 0.6 Ga), Paleozoic (from Silurian to Carboniferous) and Mesozoic (Jurassic and Cretaceous) rocks. Recently (2010) I have established a collaboration with Iraqi Kurdistan as part of a government program to boost scientific research in this country. My research led me to publish about 180 papers in international and national journals and presented more than 170 conference papers. I am a holder of eight courses at the ULB (5 mandatory and 3 optional), excursions and field stages, I taught at the third cycle in several French universities and led or co-managed a score of 20 Doctoral (PhD) and Post-doctoral theses and has been the promotor of more than 50 Masters theses.

The second shale revolution

by Nick Butler, March 13, 2017


After the dip last year, production of oil from shale rocks in the US is increasing again. Estimates for this year range from a net increase of between 400,000 and 800,000 b/d. And 2017 is not a one-off year. The Permian Basin in Texas — the main focus for the new activity — has oil reserves that exceed those of all the largest discovered fields globally, such as Ghawar in Saudi Arabia and Prudhoe Bay in Alaska

Oil below $50: OPEC’s production cap plan is backfiring as U.S. shale enters ‘near nirvana’

by Jesse Snyder, March 10, 2017


Vicky Hollub, the CEO of Occidental Petroleum Corp., speculated that Permian production could in coming years reach as high as four or five million barrels per day, up from around 2.2 million bpd today.

A confluence of factors has created “near nirvana” for the U.S. shale industry, analysts at Citi Group said in a recent research note. Among those factors was the OPEC-led agreement to curb oil supplies in an attempt to lift prices.

Country Analysis Brief: Australia

by U.S. Energy Information Administration, update March 7, 2017


Australia, rich in hydrocarbons and uranium resources, was the world’s largest coal exporter in 2015 and the second-largest liquefied natural gas (LNG) exporter in 2015.

Australia is rich in commodities, including fossil fuel and uranium reserves, and is one of the few countries belonging to the Organization for Economic Cooperation and Development (OECD) that is a significant net energy exporter. Australia sent about 68% of its total energy production (includes uranium exports and excludes total energy imports) overseas in fiscal year 2015 (July 2014—June 2015), according to data from the Australian government

Interview : les sables bitumineux au Canada

par Peter Budgell, 12 février 2016


Si le Canada est le 5e producteur mondial de pétrole (derrière les États-Unis, l’Arabie saoudite, la Russie et la Chine), il le doit à ses gisements de sables bitumineux qui le placent au 3e rang en matière de réserves prouvées (derrière le Venezuela et l’Arabie saoudite). Face à la chute des cours du brut, l’Alberta est toutefois en difficultés et le Premier ministre canadien Justin Trudeau a récemment annoncé une aide financière pour relancer l’économie de cette province pétrolière. Les sables bitumineux sont d’autre part montrés du doigt en raison de leur impact environnemental. Quel sera l’avenir de ces ressources ?

Egalement : les ressources naturelles sont-elles inépuisables?

California Megaflood: Lessons from a Forgotten Catastrophe

by B. Lynn Ingram, January 1, 2013


 43-day storm that began in December 1861 put central and southern California underwater for up to six months, and it could happen again

Geologic evidence shows that truly massive floods, caused by rainfall alone, have occurred in California every 100 to 200 years. Such floods are likely caused by atmospheric rivers: narrow bands of water vapor about a mile above the ocean that extend for thousands of kilometers.

Vision, not limbs, led fish onto land 385 million years ago

through ScienceDaily, March 7, 2017

A new study suggests it was the power of the eyes and not the limbs that first led our aquatic ancestors to make the leap from water to land. The researchers discovered that eyes nearly tripled in size before — not after — the water-to-land transition. Crocodile-like animals saw easy meals on land and then evolved limbs that enabled them to get there, the researchers argue.

Timing of global regression and microbial bloom linked with the Permian-Triassic boundary mass extinction: implications for driving mechanisms

by Björn Baresel et al., March 6, 2017, Nature


Since the early days of stratigraphy, mass extinctions were noticed to coincide with major and global sea-level changes1,2 that significantly alter extinction patterns and time-series of geochemical proxies. In the case of the Permian-Triassic boundary mass extinction (PTBME), the system boundary itself has been initially placed during a global eustatic regression3, but was subsequently placed during a global transgression4 …

Shock finding : P-T mass extinction was due to an ice age, and not to warming

Geologic Evidence of Recurring Climate Cycles and Their Implications for the Cause of Global Climate Changes. The Past is the Key to the Future

Don J. Easterbrook, 2011

Department of Geology, Western Washington University, Bellingham, WA 98225, USA


Temperatures have risen approximately a degree or so per century since the coldest part of the Little Ice Age ~500 years ago, but the rise has not been linear. Global temperatures have warmed and cooled many times in 25-35-year cycles, well before the atmospheric CO2 began to rise significantly.

Two episodes of global warming and two episodes of global cooling occurred during the 20th century (Fig. 1). Overall, temperatures during the century rose about the same as the rate of warming per century since the Little Ice Age 500 years ago.

World’s oldest fossils unearthed

by University College London, March 1, 2017


Remains of microorganisms at least 3,770 million years old have been discovered by an international team led by UCL scientists, providing direct evidence of one of the oldest life forms on Earth.

Tiny filaments and tubes formed by bacteria that lived on iron were found encased in quartz layers in the Nuvvuagittuq Supracrustal Belt (NSB), Quebec, Canada.

The NSB contains some of the oldest sedimentary rocks known on Earth which likely formed part of an iron-rich deep-sea hydrothermal vent system that provided a habitat for Earth’s first life forms between 3,770 and 4,300 million years ago …

Scrutinizing the carbon cycle and CO2 residence time in the atmosphere

by Hermann Harde, Global and Planetary Change, 24 February 2017


Highlights

An alternative carbon cycle is presented in agreement with the carbon 14 decay.

The CO2 uptake rate scales proportional to the COconcentration.

Temperature dependent natural emission and absorption rates are considered.

The average residence time of CO2 in the atmosphere is found to be 4 years.

Paleoclimatic CO2 variations and the actual CO2 growth rate are well-reproduced.

The anthropogenic fraction of CO2 in the atmosphere is only 4.3%.

Human emissions only contribute 15% to the CO2 increase over the Industrial Era.

Also this link

Diamond’s 2-billion-year growth charts tectonic shift in early Earth’s carbon cycle

Science Daily, February 23, 2017


A study of tiny mineral ‘inclusions’ within diamonds from Botswana has shown that diamond crystals can take billions of years to grow. One diamond was found to contain silicate material that formed 2.3 billion years ago in its interior and a 250 million-year-old garnet crystal towards its outer rim, the largest age range ever detected in a single specimen. Analysis of the inclusions also suggests that the way that carbon is exchanged and deposited between the atmosphere, biosphere, oceans and geosphere may have changed significantly over the past 2.5 billion years.

S. Timmerman, J.M. Koornneef, I.L. Chinn, G.R. Davies. Dated eclogitic diamond growth zones reveal variable recycling of crustal carbon through timeEarth and Planetary Science Letters, 2017; 463: 178 DOI: 10.1016/j.epsl.2017.02.001

Baffin Bay and Kane Basin polar bears not ‘declining’ concludes new report

by Polar Bear Science, February 15, 2017


The 2016 Scientific Working Group report on Baffin Bay and Kane Basin polar bears was released online without fanfare last week, confirming what local Inuit have been saying for years: contrary to the assertions of Polar Bear Specialist Group scientists, Baffin Bay and Kane Basin subpopulations have not been declining but are stable.

Combien y a-t-il de continents sur Terre ? 7 avec Zealandia !

par Christophe Magdelaine, 20 février 2017


Savez-vous combien y a-t-il de continents sur Terre ? 5 ou 6 ? Alors que la question divise encore certaines personnes, un nouveau continent caché en partie sous l'océan Pacifique vient d'être confirmé par une équipe de scientifiques après des dizaines d'années de recherche. Le 7e continent : Zealandia est maintenant officiellement reconnu.
Source : notre-planete.info, http://www.notre-planete.info/actualites/4586-nombre-continents-Terre-Zealandia

Climate models for the layman

by Judith Curry, Feb 2017


Professor Judith A. Curry is the author of over 180 scienti c papers on weather and climate and is a recipient of the Henry G. Houghton Research Award from the Amer- ican Meteorological Society in 1992. She recently retired from the Georgia Institute of Technology, where she held the positions of Professor and Chair of the School of Earth and Atmospheric Sciences. She is currently President of Climate Forecast Appli- cations Network.

Oil – Where did it come from?

by David Middleton, petroleum geologist/geophysicist,  February 18, 2017


As the biomass is buried more deeply in the sedimentary column, increasing pressure compacts it, increasing temperature cooks it and over time, the hydrocarbons slowly migrate toward the surface because they are less dense than connate/formation water. The kerogen first cooks to heavy oil, then light oil, then wet thermogenic gas, then thermogenic light gas, then high temperature methane…

Oil – Will we run out?

By Andy May, February 17, 2017


In November, 2016 the USGS (United States Geological Survey) reported their assessment of the recent discovery of 20 billion barrels of oil equivalent (technically recoverable) in the Midland Basin of West Texas. About the same time IHS researcher Peter Blomquist published an estimate of 35 billion barrels. Compare these estimates with Ghawar Field in Saudi Arabia, the largest conventional oil field in the world, which contained 80 billion barrels when discovered. There is an old saying in the oil and gas exploration business “big discoveries get bigger and small discoveries get smaller.” …

Scientists uncover huge reservoir of melting carbon under Western United States

by Saswata Hier-Majumder et al., February 2017

Pervasive upper mantle melting beneath the western US, Earth and Planetary Science Letters (2017). DOI: 10.1016/j.epsl.2016.12.041


New research published in Earth and Planetary Science Letters describes how scientists have used the world’s largest array of seismic sensors to map a deep-Earth area of melting carbon covering 1.8 million square kilometres. Situated under the Western US, 350km beneath the Earth’s surface, the discovered melting region challenges accepted understanding of how much carbon the Earth contains – much more than previously understood …
Read more at: https://phys.org/news/2017-02-scientists-uncover-huge-reservoir-carbon.html#jCp

Le sol, un héritage méprisé

par Ales Bartos, 16 février 2017


Étant très marginalisées sur le champ médiatique, les problématiques liées aux sols échappent largement à l'attention du public. Pourtant, la pollution et l'érosion des sols fait annuellement baisser la capacité des sols de produire des aliments en qualité et quantité suffisantes pour nourrir une population mondiale croissante. Cet article tente d'ouvrir des pistes vers une meilleure gestion des sols, physique et réglementaire, s'inscrivant dans les logiques du développement durable.
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Atlantique Nord : le risque d’un refroidissement rapide au XXIe siècle revu à la hausse

par D. Swingedouw et al., CNRS, 15 février 2017


Dans le cadre du projet européen EMBRACE, une équipe d’océanographes a réexaminé ces 40 projections climatiques en se focalisant sur un point névralgique au nord-ouest de l’Atlantique Nord : la mer du Labrador. Cette mer est le siège d’un phénomène de convection, qui nourrit à plus grande échelle la circulation océanique de retournement. Ses eaux de surface se refroidissent fortement en hiver, deviennent plus denses que les eaux de profondeur et plongent vers le fond. La chaleur des eaux profondes est transférée vers la surface et empêche la formation de banquise

Eocene global warming events driven by ventilation of oceanic dissolved organic carbon

by Ph.F. Sexton et al., Nature, 2011


‘Hyperthermals’ are intervals of rapid, pronounced global warming known from six episodes within the Palaeocene and Eocene epochs (~65–34million years (Myr) ago)12345678910111213. The most extreme hyperthermal was the ~170 thousand year (kyr) interval2 of 5–7°C global warming3 during the Palaeocene–Eocene Thermal Maximum (PETM, 56Myr ago). The PETM is widely attributed to massive release of greenhouse gases from buried sedimentary carbon reservoirs1361114151617, and other, comparatively modest, hyperthermals have also been linked to the release of sedimentary carbon36111617

Egalement, une synthèse en français