Dr Richard J Hubbard (UK) Introduction The Thanet Anticline is an uplifted area forming the northeast corner of Kent and is home to the four coastal towns of Birchington, Margate, Broadstairs and Ramsgate (Fig. 1). Historically, the area has been known as the Isle of Thanet and, in this article, I will look at sediment deposition and erosion around the upstanding anticlinal structure and how shorelines have shifted during the past two thousand years. I will finish with some thoughts about how shorelines might look one hundred years from now. The article is based on material drawn from three guidebooks published by GeoConservation Kent, written by Geoff Downer and myself (see below). Fig. 1. The Isle of Thanet. Sketch map of northeast Kent to show the geography of the Wantsum Channel at the time of the Roman occupation. Today’s shoreline is superimposed with some medieval settlements added for orientation. The Isle of Thanet is elevated and forms an ‘island’ because of the underlying structural geology. Note the location of the offshore seismic line published by Ameen (1995), on which the cross section of Fig. 4 is based. (Figure 87 from The Smugglers Trail, Hubbard & Downer, 2021.) This article has also been written to accompany a book review that was recently published by Deposits (see Book review: The Smugglers Trail – Geology of the Thanet Coastline from Broadstairs to Cliftonville, by Richard Hubbard and Geoff Downer). Thanet has been a high standing area for more than 300 million years and … Read More
By David N Thomas and David G Bowers The extent to which our planet is covered by oceans and seas (about 70%), and the increasing concern that right-minded people have about climate change, means that there is a both a desire and an urgent need to know more about and … Read More
Jesse Garnett White (USA) “It is no measure of health to be well adjusted to a profoundly sick society” Jiddu Krishnamurti My Great Grandfather and his son both gave me some advice at a very young age. “Never trust anyone that won’t look you in the eye when they shake your hand” and “It’s OK to pick up hitchhikers while travelling the road”. These are all positive suggestions that have proved valuable both in the States and abroad. I’ve made a number of interesting decisions in my life. One I never thought I’d make was moving back to Alaska. I’ve told colleagues, dozens of friends, family members and myself, “I’ll never spend another winter in Fairbanks.”. Learning the lesson of ‘never say never’”, while travelling into the past and future simultaneously has been interesting to say the least. When a friend of 26 years heard the news, he said, “You can’t escape Covid-19, Jesse.” I completely blew that off and forged ahead. Since returning to Alaska, I’ve been fortunate to have worked with a lot of good folks, meet new friends, network, and travel around the interior and Alaska Range. I was blessed to work as a contract geologist at an open pit mine in both development and exploration roles, assist mom-and-pop miners with permitting, create an LLC, and work at what I consider the best pizza place in Alaska. Winter temperatures dipped below -50oF and snow depth at the cabin reached four feet in total. At the time of … Read More
James O’Donoghue (UK) Did the destruction of forests by mammoths make the Pleistocene Ice Age even colder? It’s an extraordinary prospect. Yet, a leading fossil mammal expert thinks they did just that. Over many tens of thousands of years, mammoths and straight-tusked elephants ate their way through vast tracts of the world’s forests. Trees exert a buffering effect on global climate – take them out and face the prospect of hotter and colder extremes. Mammoths may have turned cool Ice Age periods into freezing ones. Straight-tusked elephants may have made temperatures rise during interglacials. Both types of elephant had all but vanished by 10,000 years ago, never to return. Since then, forest cover has increased sharply while the climate has been unusually mild and stable. Could the two be linked? Humans chopping down forests are now exerting at least as profound an effect on the world’s ecosystems as the mammoths had on theirs. By comparing the destruction wrought then and now, an alarming prospect emerges. Are we in the very process of making our own climate as volatile as that of the extinct elephants? Cores drilled from undisturbed glacial ice in Greenland and Antarctica have provided a wealth of information about almost constant shifts in the Earth’s climate over the past few hundred thousand years. Climatologists will tell you that we live in an interglacial period, in a world that is still going through an ice age that started 1.8Ma with the onset of the Quaternary period. (When I refer … Read More
Stephen K Donovan (The Netherlands) Stop 1. Waterford District, near Codrington Agricultural Station (approx. 59º 36’ 8” W 13º 6’ 49” N; Fig. 1) The area considered in the final part of this guide is outlined in A field guide to Barbados (Part 1): Introduction (Donovan & Harper, 2010, fig. 1e) and Fig. 1 in this article. As with other articles in this series, the starting point is Bridgetown. Fig. 1. Locality map showing the positions of Stops 1 to 6 in central Barbados. Only those roads relevant to this excursion are shown (after Donovan & Harper, 2005, fig. 12). This figure should be used in conjunction with the geological map of Poole & Barker (1983) and any tourist road map. Key: abc = ABC Highway; B = Bridgetown; 1 = Waterford district (Stop 1); 2 = Dayrells (Stop 2); 3 = Harrison’s Cave (Stop 3); 4 = Welchman Hall Gully (Stop 4); 5 = Horse Hill (Stop 5); 6 = Hackleton’s Cliff (Stop 6); coastline stippled. From the ABC Highway, turn southwest towards Bridgetown on Highway 3. In the area of the turnoff towards Codrington Agricultural Station (on the right), in the parish of St Michael, examine the road cutting, starting at the southwest corner and walking northeast. This is Stop 6 of Humphrey & Matthews (1986, p. 101), in the Middle Coral Rock, just above the First High Cliff and dated at 194,000 years old. The succession shows a range of reef-related biologically-determined facies (that is, sedimentary rocks … Read More
Stephen K Donovan (The Netherlands) Stop 1. Chalky Mount (approximately 59º 33’ 15” W 13º 13’ 55” N; Fig. 1) The area considered in this part of the guide is outlined in Donovan & Harper (2010, fig. 1d) and Figs. 1 and 2. As with other articles in this series, the starting point is Bridgetown. Those wishing to examine the succession and structure of the Scotland District in considerably more detail than outlined below are referred to Speed (2002). This can be complimented by Patel’s (1995) discussion of the geomorphology. Readers are referred to the glossary in A field guide to Barbados (Part 2): The coastal geology of southeast Barbados Fig. 1 Locality map showing the positions of Stops 1 to 7 in the Scotland District of Barbados (after Donovan & Harper, 2005, fig. 11). Only those roads relevant to this excursion are shown. This figure should be used in conjunction with the geological map of Poole & Barker (1983) and any tourist road map. Key: C = Conset Point; H = Horse Hill; W = Welchman Hall; Stop 1 = Chalky Mount; Stop 2 = Bissex Hill; Stop 3 = Coconut Grove; Stop 4 = exposures on East Coast Road; Stop 5 = oil seep; Stop 6 = Bathsheba; Stop 7 = Bath Cliff; coastline stippled. Fig. 2 Geological map of the Scotland District of Barbados (after Donovan & Harper, 2005, fig. 2; Donovan, 2010, fig. 3; simplified after Speed, 2002, fig. 9). Key: open stipple = basal complex; … Read More
Maybe it’s a result of my social anthropology and geological background, but I found this difficult but fascinating book a great read. It’s about nineteenth century India. It is not about the modern geological science or social anthropology of the subcontinent, but rather, the geological imagination of India, as well as its landscapes and people, and its history.
Stephen K Donovan (The Netherlands) The area considered in this part of the guide is outlined in Donovan & Harper (2010, fig. 1C) and Fig. 1 of this article. As in other articles in this series, the starting point is Bridgetown. Fig. 1. Locality map showing the positions of Stops 1 to 5 on or near the south coast of Barbados (after Donovan & Harper, 2005, fig. 8). Only those roads relevant to this excursion are shown. This map should be used in conjunction with the geological map of Poole & Barker (1983) and any tourist road map. Key: A = Grantley Adams International Airport; abc = ABC Highway; C = Six Cross Roads; O = Oistins; 1 = the Barbados Museum, Bridgetown (Stop 1); 2 = South Point Lighthouse (Stop 2); 3 = Foul Bay (Stop 3); 4 = Woodbourne Oilfield (Stop 4); 5 = Chapel Quarry (Stop 5); coastline stippled. Stop 1: The Barbados Museum The Barbados Museum and Historical Society was founded in 1933. Its museum occupies St Ann’s Garrison, a nineteenth century British military prison. It is situated in the parish of St Michael, southeast of the central part of Bridgetown, behind the Garrison Savannah racetrack. The museum has displays covering many aspects of Barbadian history and life, including natural history, prehistory and maps. The library is an important research resource, containing 5,000 books, monographs and articles on the culture and natural history of the island. Articles about the island’s natural history, culture and history are … Read More
Stephen K Donovan (The Netherlands) Stop 1: Arawak Cement Quarry The area considered in this part of the guide is outlined in Donovan & Harper (2010, Fig. 1b) and Fig. 1. As with other articles in this series, the starting point is Bridgetown. Drive north from the Bridgetown area on Highway 1, the main west (or leeward) coast road, which is constructed on the Lower Coral Rock and overlies superficial deposits. Fig. 1. Locality map showing the positions of Stops 1 to 4 in northern Barbados (after Donovan & Harper, 2005, fig. 7). Only those roads relevant to this excursion are indicated (including the track to Stop 4). This map should be used in conjunction with the geological map of Poole & Barker (1983) and any tourist road map. Key: C = Content; Ch = Checker Hall; G = Greenidge; T = Trents; 1 = Arawak Cement Quarry (Stop 1); 2 = Animal Flower Cave, North Point (Stop 2); 3 = limestone cliffs west of North Point (Stop 3); 4 = Cluff’s Bay (Stop 4); coastline stippled. The First High Cliff and the Middle Coral Rock are close by in the east (Speed & Cheng, 2004). This coast has been developed for tourism and has neither the magnificent sea cliffs of the east coast, nor the impressive Atlantic breakers seen in the previous excursion. To the west, two submerged barrier reefs, at 22m and 70m water depth, are separated from the coast by a submerged wave cut terrace (MacIntyre, 1967). … Read More
Stephen K Donovan (The Netherlands) and David AT Harper (Denmark) Introduction This article is the second part of a field guide to Barbados, the first part of which is A field guide to Barbados (Part 1): Introduction. The areas visited by different the excursions outlined in Parts 2 to 6 of this guide are shown in Fig. 1. All itineraries commence from the Bridgetown area and the itinerary outlined in this part is rewritten after Donovan and Harper (2002). The words in italics and bold appear in the glossary at the end of the Part 1. Fig. 1. Relative positions of field excursions described in this field guide (after Donovan & Harper, 2005, fig. 5). (a) Southeast Barbados (Part 2). (b) North Barbados (Part 3). (c) South Barbados (Part 4). (d) Scotland District (Part 5). (e) Central Barbados (Part 6). Charles Taylor Trechmann DSc, FGS (1885-1964) (Fig. 2) was an anachronism, a twentieth century gentleman geologist and archaeologist. He was an amateur with sufficient private means to dedicate his time and use his scientific abilities to make an original contribution to his chosen field of study, an original thinker with a desire to use his observations to interpret broad geological phenomena. He devoted his time to research on Malta, Gibraltar, New Zealand and, particularly, northeast England and the Caribbean. He published over 80 monographs and research papers on geology and archaeology, including at least 40 on the Caribbean (Donovan, 2003, 2008, 2010a). Fig. 2. Charles Taylor Trechmann, DSc, FGS (1884-1964) … Read More
Stephen K Donovan (The Netherlands) This is the first of six articles that will introduce the geology of the Antillean island of Barbados. It is an expanded and more detailed guide derived from two earlier publications (Donovan & Harper, 2005, 2009). The structure of the guide will include a summary of the geology of the island (in this part) and five, one-day field excursions for the geologically-biased tourist. These excursions will introduce the stratigraphy, structure and geological history of Barbados (Figs. 1 and 2), a small Antillean island shaped like a contorted teardrop, about 34km long by 24km at its widest. Fig. 1. The principal features of the geological history of Barbados summarised in a single section at Spring Bay, parish of St. Phillip, on the southeast coast. Professor David Harper (University of Copenhagen) is looking northwest, towards Ragged Point (Fig. 2) and admiring the angular unconformity between the allochthonous Palaeogene basal complex (=Scotland Beds) and the overlying autochthonous bedded limestones of the Pleistocene Coral Rock. A visitor to the island, who wants to undertake fieldwork, should hire a car. The only other reliable forms of transport are bus and taxi. While cheap, buses tend to stick to the main routes, particularly in the countryside. However, the size of the island means that localities are rarely more than a few kilometres from a bus stop. If money is no object, a taxi driver will be happy to drop you at a site in the morning and collect you at a … Read More
Jack Wilkin (UK) Palaeoclimatology is the study of past climates and environments using climate proxies, that is, the preserved physical characteristics of past, rather than using direct measurements of variables, such as temperature, levels of CO2 and so on. Many different types of proxies are used including, but not limited to, ice cores (Petit et al., 1999), lake and ocean sediments (Cehn et al., 1999), and fossil data. Many fossil groups have specific environmental and ecological tolerances and so can be used to determine palaeotemperatures and palaeoclimates (Jones, 2006). It is the data collected using dendroclimatology and other plant macrofossils that will be examined in this article. Dendroclimatology Dendroclimatology is the use of tree rings to determine long-term climatic trends. This is in contrast to dendrochronology, which is dating using tree ring data. Dendroclimatology is used extensity to study the climate during the Holocene (Fig. 1) but has also been applied to the Late Cretaceous of Alaska and even the Permian of Antarctica (Taylor et al., 2009). The thickness of the tree rings helps scientists work out how much the trees had grown within a given year. Then, by comparing the rate of growth to members of the same, or closely related, genera or species, they can determine the palaeoenvironment. Fig. 1. Variations in tree ring width translated into summer temperature anomalies for the last 7,000 years, based on samples from Siberia. Source: Institute of Plant and Animal Ecology https://upload.wikimedia.org/wikipedia/commons/5/53/Yamal50.gif. Dendroclimatology can also be used to gather isotopic data. As … Read More
If you can see past the somewhat robust title (a reference to James Hutton’s discomfort riding around Scotland on horseback during his geological investigations), this is an interesting read, combining both geological science and humour in just about the right measures.
Jan Willem van der Drift (The Netherlands) Historic finds In 1900, nobody knew what kind of tools man used before the handaxe. Some scholars assumed that early-man used ‘eoliths’ – handy natural forms. That theory turned out to be false. The earliest tools were manmade flakes and cores, and this is now called Mode-I. James Reid Moir was one of the first to make claims about such tools and Fig. 1 shows a flake on which Reid Moir wrote that it came from below the Weybourne Crag near Cromer. Fig. 1. This flake was found over a century ago by Reid Moir (drawing from reference 1). However, the flaking angles, the form of the bulb and other fracture-signals on Reid Moir’s flakes differ slightly from what we see on flakes found in Neolithic sites or in connection with handaxes. This led most archaeologists to believe that Reid Moir’s flakes were not manmade. Rediscovery In the 1980s, Dutch collectors found pebble tools in aggregate that was dredged from the sea, offshore from Norfolk. A group of four collectors (Ab Lagerweij, André Cardol, John de Koning and Herman van der Made) decided to visit East Anglia and search for sites on land. They hoped to find pebble tools in the Cromer Forest Bed, which is a freshwater deposit dated to the Cromerian, which contains fossils from steppe mammoth, rhinoceros and horse. The Anglian glaciers covered this formation with sand, gravel and till, but it lies exposed on the coast. The four did … Read More
Robyn Molan (Australia) Fig. 1. The location of the excavations. In an article in the Australian Age of Dinosaurs Journal (Issue 6, 2008) I dubbed the period between 1984 and 1994 ‘a decade of dedication’, thanks to the persistence of an American-Australian team headed by palaeontologists Tom Rich and his wife, Pat Vickers-Rich. (Tom wrote an article for Deposits, entitled Tunnelling for dinosaurs in the High Arctic.) This was the decade that brought to the world the fascinating polar dinosaurs of south-eastern Australia and the eventual naming of three new dinosaur species – with a few other surprises along the way. Two hundred and twenty kilometres west of Melbourne, on the Otway Coast of Victoria, Australia, is a remote and little-known inlet. Set in a stretch of steep, rugged shoreline, this isolated cove is pounded by the Southern Ocean and blasted by Antarctic winds. Nearby, the world-renowned rocky sentinels, ‘The Twelve Apostles’ (see the cover of Issue 20 of Deposits), stand testament to the power of wave and wind, as they beckon tourists who travel the Great Ocean Road. Fig. 2. The rugged beauty of Dinosaur Cove. (Photo Ros Poole.) The excavation at Dinosaur Cove, as the inlet later became known, was the first major dinosaur dig conducted in Victoria. For several weeks each summer, the Rich family, and a crew of hardy volunteers, battled untold obstacles to wrestle fossils from the base of the cliff. It was gruelling, dirty and dangerous work, but subsequent scientific research on what was … Read More
Dr Thomas H Rich (Australia) Fig. 1. Location of the Liscomb Bonebed. (© Thomas Rich.) I have no idea what made me look up at that moment. But, when I did, I saw a flash of light reminiscent of the sun glinting off the wings of a flock of birds abruptly and simultaneously changing direction. However, the light was not from a flock of birds. Rather, it was from thousands of individual, fist-sized lumps of rock, together with lumps of half-frozen mud on the steep slope above me. They were glistening due to a film of meltwater covering them and they were simultaneously starting to roll because the tonnes of rock on which they lay had suddenly started to collapse and plummet down towards me on a journey that would end in the frigid waters just below my feet. At that moment, I was digging into permafrost at the base of the steep slope forming the left bank of the Colville River that flows across the North Slope of Alaska and terminates in the Arctic Ocean about 40km further downstream. (The North Slope is the tundra covered coastal plain in northernmost Alaska bordered on the north by the Arctic Ocean and 250km to the south by the east-west Brooks Range.) Like my companions, my efforts were directed towards recovering ‘polar dinosaurs’, at a locality named the Liscomb Bonebed in honour of the geologist who found it in 1961. Fortunately, the tonnes of mud and claystone that cascaded down the bank … Read More
Sea level change is something that probably everyone who does their best to keep up to date about climate change, thinks they know about and on which they will have an opinion.
Another issue of Deposits and another excellent addition to the “Introducing Earth and Environmental Sciences” series by Dunedin, many of which I have favourably reviewed in this magazine.
Roy Bullard (UK) There are many places around the coastline of the British Isles that are quite simply majestic and, in their own unique ways, full of magic. Dunwich lies between the lovely town of Southwold and the village of Sizewell on the East Coast of England in the county of Suffolk. It is a coastal area that is easy to include in this category and is a place that I love to visit. However, as you sit there on the shore watching the cliffs and the North Sea, it is hard to imagine that so much has been lost since the time when Dunwich was once a large, thriving community. Fig. 1. Sandy cliffs of Dunwich. My aim in this short article is to take a look at the present state of this coastline and compare it with the coast as it once was before huge amounts of coastal erosion had taken place. In addition, I will take a look at the area’s history and mention, in passing, one of its well-worked, mythical tales. A steeply sloping shingle beach now lies in front of the cliffs at Dunwich. These cliffs have changed a lot over time but, over the past few years, erosion has decreased substantially. The cliffs today are overgrown and this indicates a significant slowdown in the rate of erosion. However, with the ongoing threat of climate change and rising sea levels, the local residents and council have joined together to act now to protect the northern … Read More
Joanne Ballard and André Bijkerk (USA) In this article, we will argue that the extinction of megafauna on the mammoth steppes of the Northern Hemisphere may ultimately have been caused by the release of massive quantities of methane in the North Atlantic Ocean at the Amazon Fan near the Brazilian coast and also from the Ormen Lange gas field off the coast of Norway. We will suggest that these events caused significant changes in the flow of water at the surface of the ocean that, in turn, led to very rapid changes in the levels of rainfall. Scientists have already recognized that increased precipitation gave rise to changes to ecosystems (or, more precisely, to biotopes) that destroyed the mammoth steppe. However, much of the evidence we will use in this article to support our argument has been used to support other sorts of explanation for the extinction. Therefore, this primary evidence now appears to be in need of revision. Introduction About 11,000 years ago, all of the remaining herds of mammoths suddenly disappeared. During the Pleistocene, these mammoths once thrived on a vast, megafauna steppe stretching across the Northern Hemisphere. It may have resembled the African steppes of today with lions, hyenas and several species of large grazers being present. However, the debate about the cause(s) of the extinction continues. In North America, things appear to be simple – the appearance of early humans on that continent seems to coincide with the downfall of the megafauna. However, there are also … Read More
Margret Steinthorsdottir and Helen K Coxall (Sweden) Near the small town of Clarkia in Shoshone County, Idaho in the USA, exists a rich and unique fossil deposit. The Clarkia fossils, or Clarkia Flora, as the deposit is mostly called due to the abundance of fossil plants, is so well preserved that the assemblage is referred to as a “lagerstätte”, a scientific term reserved for the world’s very finest fossil deposits. The Clarkia fossils are found in sediments that are now known to be about 16 million years old and belong to a period in Earth history called the Miocene. By this time, the (non-avian) dinosaurs were long extinct (the last of these dinosaurs disappeared about 66 million years ago), the Earth’s continents were more or less in the same position as today, and many of the animals and plants would have started looking familiar to modern humans (who emerged much later, about 200,000 years ago). Fig. 1. The entrance to the “Fossil Bowl” motocross racetrack and fossil locality near Clarkia, Idaho. Among the Clarkia fossils can be found various insects, fish and occasionally the remains of small mammals. However, most striking is the wealth of plant fossils in the form of exceptionally well-preserved leaves, nuts, seeds and wood. Impressively, one can find leaves of oak, laurel, pine and birch that look virtually identical to those we find today. If you look quickly when a new fossil is newly exposed from within the host sediments, you may occasionally even see the … Read More
Deborah Painter (USA) Imagine a tremendous piece of land moving equipment that scraped up the soil and some of the surface bedrock from four states within the United States’ Eastern Seaboard, carrying and dragging it all the way, before dumping it on a ridge off the shoreline. That is what essentially occurred with the final advance of the Wisconsinian ice sheet, the only one which left glacial deposits visible in New York State today. Long Island is a ridge of Cretaceous bedrock with glacial deposition. The moraines there have not been ground into sandbars and spits along the western end of the north shore as much as elsewhere, because of the sheltered nature of the Long Island Sound. Therefore, shoreline bluffs expose rocks as well as glacial loess. Fig. 1. Fishermen’s Drive takes you to the loess deposits. To park at the beach requires a permit. (Photo by JB Steadman.) If you find that your journeys take you to New York City, one of the world’s largest metropolitan areas, try to make time to visit Caumsett State Park at Long Island Sound. My own visit began when planning a visit to New York State’s Long Island to see my friend, Joyce Raber. She suggested various things that we might do: go to a Broadway play, go shopping and so forth. However, my list of things to do was typically “eco-tourist”. I wanted to visit the famed American Museum of Natural History in Manhattan, then see nearby Central Park, where the … Read More
Arthur Speed (UK) One hundred and eighty million years ago in the Toarcian Stage of the Lower Jurassic Period, the Earth was very different from the world we know today. The continents were all clumped together in a supercontinent called Pangaea, which was just beginning to split apart. Sea level was approximately 100m higher than at present, such that much of Britain (including Yorkshire) lay beneath shallow seas. At this time, the Earth’s oceans were depleted in dissolved oxygen. The chain of events that caused this are complex, but can be traced back to a major volcanic event (Fig. 1). The eruption of the Karoo-Ferrar Large Igneous Province (LIP) spewed lava over what is now southern Africa and released vast amounts of carbon dioxide into the atmosphere. Just as happens now, the carbon dioxide resulted in global warming, which, in turn, had several effects on the oceans: Fig. 1. Volcanism during the eruption of the Karoo-Ferrar LIP may have triggered the Toarcian Oceanic Anoxic Event (Ulrich, 1983). Seawater became deficient in dissolved oxygen, because oxygen solubility decreases with increased temperature.Plankton thrived as a result of the warmer temperatures and increased nutrient supply, using up even more dissolved oxygen.Oceanic circulation was decreased, reducing the supply of cold oxygenated water to the oceanic basins.Warmer water released the green-house gas methane from the ocean floor, further accelerating global warming.The result was the formation of a layer of water that was deficient in oxygen throughout the Earth’s oceans. Its existence was first postulated in … Read More
Khursheed Dinshaw (India) In this article, I will briefly deal with the fascinating and relatively recent geological transformation of the Sharjah region of the United Arab Emirates (UAE). Sharjah needs no introduction in terms of it being a popular tourist destination, especially for families. However, very few know how it was formed and subsequently transformed. In this article, I hope to explain this fascinating aspect of Sharjah. From the beginning At the beginning of the Miocene Period, 23 Ma, Arabia finally split from Africa along the Red Sea and the Gulf of Aden became a separate plate. This new plate moved in a northerly direction and collided with, and was subducted under, the Eurasian continent (Fig. 1). The Strait of Hormuz also closed as the remains of the Tethys Ocean formed a rapidly subsiding basin in which thick layers of salt were deposited. Large scale folding and faulting took place in the UAE producing hills of folded rock, such as Jebel Fai’yah and Jebel Hafit. Fig. 1. Granite from continental drift. In the eastern part of the UAE, uplift of the Al-Hazar Mountains began. This continued into the Pliocene Period, from 5 to 2 Ma. In the late Miocene and Pliocene, the Sharjah region finally rose above sea level and the landscape we see today was formed. Fig. 2. Various rock exhibits at the Sharjah Natural History and Botanical Museum. When the region known as Sharjah rose above sea level, it allowed the area to be covered by the moving … Read More
Steven Wade Veatch (USA) and Vishwam Sankaran (India) “There’s nothing new under the sun” goes a famous saying and these words are very apt when trying to understand Earth’s climate trends. Thanks to numerous discoveries made about Earth’s ancient past, we now know that our climate has never been static. According to geological and palaeontological records, climate change has affected the Earth throughout geologic time. In this context, this is the second of a series of articles about climate change over geological time. The first is A warming medieval climate supports a revolution in agriculture by Steven Wade Veatch and Cheryl Bibeau. To understand climate change today, researchers study past climates and events that affect climates, such as volcanic activity, solar radiation, sunspot activity, astronomical changes and other factors that influence climate. Once we understand the dominoes that have fallen during the past climate change events, we can understand and predict – to some degree – the kind of patterns that may follow current trends. To do this, scientists piece together clues from past climates provided by rock formations. Scientists likewise examine fossil records that yield climate signals from the past. These fossils range from prehistoric pollen to dinosaurs. Putting both geological and fossil records together reconstructs ancient climates and environments. More recent climate change is studied through climate records held in polar ice caps and ice sheets, ice cores, glaciers, isotopes of elements (like oxygen, carbon and sulphurfur), soil sediments and tree rings. When we think of the term … Read More
David Wharton-Street (UK) Whatever your views, this is a subject that will not go away, and the concept of the Anthropocene is gaining more impetus and consideration as time goes by. In a nutshell, the Anthropocene has been proposed as a new third epoch of the Quaternary Period that directly relates to anthropogenic environmental impact on the Earth’s climate, land, oceans and biosphere, on a globally-recognisable scale. The Anthropocene would begin directly after the termination of the Holocene Epoch, but much debate and controversy currently relates to when exactly that date should be – should it begin thousands of years ago, perhaps relating to when our ancestors began widespread agricultural clearances? Should it begin with the Industrial Revolution or during the Second World War? In fact, some scientists even consider that it should begin as recently as the 1960s. Interestingly, the term ‘Anthropocene’ only came into being very recently, in 2000, when a Dutch Nobel Prize-winning chemist named Paul Crutzen made an off-the cuff comment at a press conference and, just a few years later, the International Commission on Stratigraphy (ICS) Working Group on the Anthropocene was formed. Paul Crutzen rightly drew attention to mankind’s influence on the planet and the need to guide society through man’s impact (mostly deleterious). The designation of ‘Anthropocene’ as the epoch of ‘mankind’s influence’ is used to enhance the gravity of the way that man is destabilising earth’s natural systems. However academically satisfying it is to promote a concept, it is quite a different … Read More
Mark Wilkinson (UK) Practically everyone has an opinion on climate change by now, although for the vast majority of scientists, the weight of evidence is overwhelming – emissions of carbon dioxide and other greenhouse gases are causing climate change, sometimes referred to as global warming. One possible technology for fighting climate change is Carbon Capture and Storage (CCS) in which geology plays an important role. In fact, future generations of geologists may be employed searching for CO2 storage sites in the subsurface, rather than for the more traditional search for oil and gas. The aim of CCS is simple – to allow the continuing use of fossil fuels while reducing the emissions of greenhouse gases into the atmosphere. In the long term, the burning of fossil fuels will probably cease, but until we can rely on renewable sources of energy, we are stuck with these fuels as a cheap and reliable energy source. CO2 is emitted during many activities, including driving cars and heating homes, but the largest single sources are fossil fuel power plants, which generate electricity, followed by industries, such as steel works and cement plants. It is these that most research has been focussed on. And, in principle, the technology is simple – capture the CO2 from a source (such as a power plant; Fig. 1) before it gets into the atmosphere, then transport it to a suitable storage site and inject it into the ground where it will remain for tens of thousands of years. Fig. … Read More
Dr Thomas H Rich (Australia) The Cenozoic Era is commonly referred to as the ‘Age of Mammals’. That is certainly the time in the history of life when their fossils are most abundant and diverse. However, two-thirds of mammalian history was during the Mesozoic Era – and they appeared about the same time as the dinosaurs. All continents except Antarctica have some record of the early, Mesozoic mammals. Of those that do, Australia has the most meagre record of all. Despite this, with this landmass that today has the most distinctive terrestrial mammals on the planet, their Mesozoic origins are so enigmatic that it has motivated a major effort since 1984 to search for fossils of those mammals that lived alongside the dinosaurs on this now isolated continent. Fig. 1. A map of Australia showing the location of the four sites where Cretaceous mammals have been found on the continent. During the Cretaceous, Australia was much further south than at present. Shown here are the lines of latitude at that time on the continent: 50o south, 60o south and 70o south. The famous Lightning Ridge opal field has provided some of the answers – two different early Late Cretaceous egg-laying mammals (the monotremes), as well as a third mammal that may be a monotreme, have been discovered there. One thousand, three hundred kilometres to the south-southwest along shore platforms pounded by the waves of the Southern Ocean, which expose those rocks on south coast of the continent, are three sites … Read More
Neal Monks (UK) The extinctions at the Cretaceous-Tertiary (K/T) boundary make up what is probably the most famous geological event in popular culture. This is the point when the great reptiles that characterise the Mesozoic went extinct. Alongside the dinosaurs, the giant marine reptiles died out too, as did the pterosaurs, and a whole host of marine invertebrates, including the ammonites and belemnites. What happened? Some geologists argue the climate changed over a period of a million years or more, thanks to the massive volcanism that created the Deccan Traps in India. Others maintain that the K/T extinctions happened suddenly, pointing to evidence of a collision between the Earth and an asteroid. Perhaps there wasn’t a single cause, but rather a variety of factors: volcanism, climate change, asteroid impact, underlying changes in flora and fauna, and perhaps even variation in the output of the Sun and resulting weather patterns. That life on Earth can be wiped out this way is the stuff of disaster movies as much as TV documentaries. However, what comes as a surprise to many people is that there wasn’t just one mass extinction at the K/T boundary, but a whole series of them that can be observed throughout the fossil record. One of them, the Permo-Triassic extinctions, appear to have been even more catastrophic than the K/T extinctions, and at least three other extinction events are comparable in scale. In between these five big extinctions were lots of smaller extinctions that aren’t well studied, but had … Read More
Steven Wade Veatch and Cheryl Bibeau (USA) In the light of our current worries about climate change and global warming, this is the first a series of articles for Deposits that covers significant climate changes that have occurred in the geological past and times when the earth’s climate was hugely different from what we know today. However, this first one covers a slightly more recent event – the Medieval Warm period. The twenty-first century has had some of the hottest temperatures on record, but there was another period that was just as warm or warmer. The Medieval Warm Period (approximately 900–1300 AD), refers to the time when temperatures in Europe and nearby regions of the North Atlantic are thought to have been similar to, or in some places exceeded, temperatures of the late twentieth century. Researchers believe changes in the circulation of the Atlantic Ocean brought warmer waters to the North Atlantic and neighbouring regions, causing warming temperatures. The Medieval Warm Period was followed by the Little Ice Age (approximately 1300-1850 AD), a period of cooling that brought colder winters and advancing glaciers to parts of Europe and North America that lasted well into the nineteenth century. Scientists have evidence of this unusual warming period through indirect estimates of temperatures based on climate indicators that include tree rings, Greenland ice cores, ocean sediments and, in certain regions, written evidence of crop yields. There are even recorded dates when leaves come out and when flowers bloom in the spring. Records show … Read More