Geology Today最新文献

{"title":"Rocks explained 2: Basalt","authors":"Kent Brooks","doi":"10.1111/gto.12414","DOIUrl":"10.1111/gto.12414","url":null,"abstract":"<p>Basalt is a fairly familiar word, although few laymen could define it. In fact, basalts are the commonest rocks of the Solar System. On Earth, they are found in all tectonic settings and of all ages throughout geological time. Basalts are volcanic rocks, rich in magnesium and poor in silica, consisting of plagioclase (with a composition in the labradorite range) and the mafic minerals: olivine, pyroxene, iron oxides and sometimes hornblende. They are dark-coloured, fine-grained (although larger crystals, known as ‘phenocrysts’ or ‘megacrysts’ may occur) and are typically found as lava flows. Basalt makes up enormous accumulations, often over 1 million square kilometres in size, known as ‘large igneous provinces’ or LIPs, which may be associated with mass extinctions. Other, more siliceous, rocks are hypothesized to be derived from basaltic magmas by the process of igneous differentiation.</p>","PeriodicalId":100581,"journal":{"name":"Geology Today","volume":"38 6","pages":"236-242"},"PeriodicalIF":0.0,"publicationDate":"2022-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78519299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"African sandstorms, blood rain and continental mineral delivery to the Canary Islands","authors":"Valentin R. Troll,&nbsp;Juan Carlos Carracedo,&nbsp;H. Albert Gilg","doi":"10.1111/gto.12412","DOIUrl":"10.1111/gto.12412","url":null,"abstract":"<p>The origin of volcanism in the Canary Islands has been a matter of controversy for decades. Discussions have hinged on whether the Canaries owe their origin to seafloor fractures associated with the Atlas Mountain range or to an underlying plume or hotspot of uprising hot material from the deep mantle. The debate has recently concluded, however, following the discovery of nannofossils preserved in the products of the 2011–2012 submarine eruption at El Hierro, which constrain the age and growth history of the westernmost island of the archipelago and so cement a clear East to West age progression within the archipelago. Light-coloured, quartz-bearing pumice-like ‘floating rocks’ (xeno-pumice) were found on the sea surface during the first days of the 2011 El Hierro eruption and proved to be fragments of pre-island, sedimentary strata that were picked up by ascending magma. Upper Cretaceous to Pliocene calcareous nannofossils such as coccolithophores were retrieved from the xeno-pumice fragments, and these marine micro-organism biostratigraphical markers now provide crucial evidence that island growth at El Hierro commenced in the Pliocene. Here we discuss how these essentially continental (quartz-bearing) sediments on the African continental shelf derive from dominantly wind-blown Sahara dust and marine (re)-deposition and describe present-day aeolian processes that are in operation in the region. We investigate the mineralogy of Sahara dust that is currently deposited in the Canary Islands and discuss source areas and intra-transport fractionation of mineral dust during trans-Atlantic transport. Finally, we explore how present-day dust deposition can be used as analogue to explain the deposition of pre-island continental material in the East-Atlantic Ocean basin beneath the Canary archipelago and we show how the dust-derived sedimentary deposits can be utilized as geological tool in the Canary Islands.</p>","PeriodicalId":100581,"journal":{"name":"Geology Today","volume":"38 6","pages":"218-229"},"PeriodicalIF":0.0,"publicationDate":"2022-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gto.12412","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85039023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The role of active geological structures in forming hot springs in Ramsar, Iran","authors":"Hasan Alizadeh","doi":"10.1111/gto.12413","DOIUrl":"10.1111/gto.12413","url":null,"abstract":"<p>The hot springs of Ramsar, Iran are located at the northern zone of the Central Alborz Mountain Range along the Caspian Fault. Ramsar is a well-known area with amongst the world's highest levels of natural radiation. Due to the local geology, which includes high levels of radium in rocks, soils, and groundwater, Ramsar residents are also exposed to high levels of alpha activity in the form of ingested radium. Nine springs were selected from the hot springs of Ramsar for this research, and water samples were tested to find the amount of dissolved materials and elements. Analysis of the results suggests that the hot springs of Ramsar originated from the sea. The results indicate that coincident with subduction of the southern Caspian basin and obduction of the Central Iranian crust over the southern Caspian crust, saline seawater reaches fracture zones of the Caspian Fault where it is heated due to mixing with radioactive materials and release of radon as a result of activity of the faults and its decay into radium. Then it migrates along the Caspian thrust faults and forms hot springs originated from regional surface waters of Ramsar. Those hot springs located next to thrust faults were the result of collision, and the origin of neighbouring cold springs is karst.</p>","PeriodicalId":100581,"journal":{"name":"Geology Today","volume":"38 6","pages":"230-235"},"PeriodicalIF":0.0,"publicationDate":"2022-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89273448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geodigest","authors":"","doi":"10.1111/gto.12405","DOIUrl":"10.1111/gto.12405","url":null,"abstract":"When the penguins ‘poop’ on Antarctica’s Elephant Island, chemical reactions in the soil produce a dull brown mineral called spheniscidite (Jonathan Amos, BBC News, 2 July 2022). This mineral is unique and reflects the special conditions that exist only in that locality. The name comes from Sphenisciformes—the group to which penguins belong. Spheniscidite is just one of roughly 6000 such minerals that have been officially recognized recently by the International Mineralogical Association (IMA). But there have been some changes. Robert Hazen from the Carnegie Institution for Science in Washington DC has spent the past 15 years reclassifying the minerals to add information about their genesis. ‘There’s been a classification system in place for almost two centuries that’s based on the chemistry and the crystal structure of minerals, and ours adds the dimensions of time and formation environment’, he told the BBC. With colleague Shaunna Morrison, Hazen has tried to give the thousands of different mineral species some extra context, making the point that you cannot truly appreciate the significance of a mineral unless you also understand how and when it formed. Their research shows nature has used 57 ‘recipes’ to create 10 500 of what they like to call ‘mineral kinds’—by crushing, zapping, boiling, baking and more. For instance, water, they say, has helped more than 80 percent of mineral species to form. Biology has had a direct or indirect role in the creation of about 50 percent of mineral species, with onethird formed exclusively through biological processes. ‘Life affects minerals in various ways,’ explained Hazen. ‘For example, photosynthesis produces oxygen. Oxygen is a very reactive gas, and it changes the surface of Earth by oxidizing minerals. So more than 2000 new minerals formed on Earth as a result of oxygen in the atmosphere. But of course, life also creates its own minerals, biominerals. These are shells, teeth, bones, and other structures in organisms that are purposefully deposited and sculpted in the most amazing nanotechnology kinds of ways. Scientists and engineers would love to be able to reproduce what life is able to do’. Between them the scientists have built a database of every known process of formation for every known mineral species, 5659 of them in the IMA catalogue. For each mineral, they considered the ‘recipe’ needed to form them: the particular physical, chemical or biological processes involved. They found that some 40 percent originated in more than one way. According to Hazen: ‘The previous system of mineralogy said calcite is calcite; that is calcium carbonate in the calcite crystal structure, that is a species. But we say no, no, no—there are 10, 15 maybe 20 different kinds of calcite (Fig. 1), because the calcite deposited by a shell is very different from the calcite that forms on the ocean floor through just chemical precipitation, or calcite formed deep within the Earth in a process of metamorphism—of high pres","PeriodicalId":100581,"journal":{"name":"Geology Today","volume":"38 5","pages":"162-174"},"PeriodicalIF":0.0,"publicationDate":"2022-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73706551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fossils explained 82: Belemnites: Anatomy, ecology, applications","authors":"Jack Thomas Rhodes Wilkin","doi":"10.1111/gto.12409","DOIUrl":"10.1111/gto.12409","url":null,"abstract":"<p>Belemnites are extinct cephalopods that evolved in the early Late Triassic (~240 Ma) and became extinct at the Cretaceous/Palaeogene boundary (66 Ma), at the same time as the extinction of the dinosaurs. Their bullet-shaped internal skeleton, called a rostrum, are commonly found alongside the much more famous coiled ammonites. Whereas ammonites have gone on to become a universal symbol of palaeontology, belemnites are often overlooked by fossil hunters. The intention of this short introduction to belemnites is to furnish a greater appreciation for these fascinating creatures. Not only were they an incredibly important component of Mesozoic marine ecosystems and their exceptionally preserved fossils can tell us much about coleoid diversity throughout geological time, it is their applications that set belemnites apart from other macrofossils. Belemnite geochemistry can provide high-resolution data regarding past ocean chemistry and temperatures. Such information is vital in the reconstruction of Mesozoic climate systems.</p>","PeriodicalId":100581,"journal":{"name":"Geology Today","volume":"38 5","pages":"194-200"},"PeriodicalIF":0.0,"publicationDate":"2022-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76370904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Retro review: Fossils","authors":"S. Kenneth Donovan","doi":"10.1111/gto.12408","DOIUrl":"10.1111/gto.12408","url":null,"abstract":"<p>The monographs of the <i>New Naturalist</i> book series have been a source of information for natural historians in the British Isles since the 1940s. Unlike the books dedicated to birds, insects, plants and other aspects of our natural environment, the only volume devoted specifically to <i>Fossils</i> was first published in 1960. Over 60 years later, is it still worthy of our attention?</p>","PeriodicalId":100581,"journal":{"name":"Geology Today","volume":"38 5","pages":"190-193"},"PeriodicalIF":0.0,"publicationDate":"2022-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77462513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The threatened karst of the Great Western Lakes, Ireland","authors":"Michael J. Simms,&nbsp;Matthew A. Parkes","doi":"10.1111/gto.12407","DOIUrl":"10.1111/gto.12407","url":null,"abstract":"<p>Limestone is a notoriously leaky rock. In many areas that are underlain by limestone, surface rivers are few and disjointed. They disappear into sinks only to reappear, sometimes many kilometres away, at springs. It is not an environment in which lakes are typically found. Some 40 percent of Ireland is underlain by limestone, yet the Irish lowlands are scattered with countless lakes, large and small. In many the limestone beneath is effectively sealed by a cover of glacial till; others have formed where hollows descend below a shallow water table. Around the shores of many, exposed limestone bedrock and boulders support a range of peculiar etched features that are virtually confined to this lakeshore environment.</p>","PeriodicalId":100581,"journal":{"name":"Geology Today","volume":"38 5","pages":"185-189"},"PeriodicalIF":0.0,"publicationDate":"2022-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79717941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Travertine cascades","authors":"Tony Waltham","doi":"10.1111/gto.12406","DOIUrl":"10.1111/gto.12406","url":null,"abstract":"<p>Travertine is widespread in karst terrains, and less so elsewhere, and some of its varieties constitute spectacular landforms, many of which become popular visitor sites for geologists and non-geologists alike. Among the many forms of travertine, barrages are the most spectacular, especially where they still have streams or rivers cascading over them. Carbonate travertine is polygenetic, both chemical and organic, and both karstic and geothermal, with a full range of sites between those extremes.</p>","PeriodicalId":100581,"journal":{"name":"Geology Today","volume":"38 5","pages":"175-184"},"PeriodicalIF":0.0,"publicationDate":"2022-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89710376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Minerals explained 62","authors":"Kent Brooks","doi":"10.1111/gto.12404","DOIUrl":"10.1111/gto.12404","url":null,"abstract":"<p>Eudialyte is a mineral unfamiliar to most people. This is likely to change in the near future, as this mineral is of increasing economic importance. Eudialyte is now known to be one of a group that has grown in number to a remarkable extent in recent years, and eudialytes are index minerals for a specific category of igneous rocks and are repositories for elements, such as the rare earths, which have become increasingly critical to modern technology. The eudialyte group now comprises about 50 members of which about 29 members are fully recognized, and exploitation of eudialyte group minerals will soon be a reality. The mineral's name comes from Greek: Eu διάλυτος, meaning ‘well decomposable’—a reference to the fact that, unlike the highly refractory zircon (the common source of zirconium), eudialyte is soluble in common acids, making it relatively cheap to work.</p>","PeriodicalId":100581,"journal":{"name":"Geology Today","volume":"38 4","pages":"156-160"},"PeriodicalIF":0.0,"publicationDate":"2022-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78114766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mendrisio, Château-d'Oex and Sargans geological maps of Switzerland: free online data viewer and downloads","authors":"David A. G. Nowell","doi":"10.1111/gto.12403","DOIUrl":"10.1111/gto.12403","url":null,"abstract":"<p>The Swiss continue to publish highly detailed 1:25 000 geological maps and memoirs, coupled with informative cross sections. They are presented in attractive plastic wallets with a geological time scale on their back including stage names for deciphering partly abbreviated keys in whichever regional language. Swisstopo has also put free downloads of all their geological maps online, including out of print editions. This makes economic sense, given publication represents a small fraction of the overall costs incurred in surveying each sheet. In addition, they have developed an easy-to-use online data viewer where different layers of cartographic information can be selected and mixed together to produce bespoke, ready-to-print pdf downloads complete with a scale bar. Though, unlike digital data, which may become corrupted, printed material can survive for centuries. The first sheets in this national atlas were published in 1930, and so when their coverage is finally completed within roughly the next decade, policy makers would be wise to start resurveying older editions to keep them up to standard. In this way, Switzerland can maintain enough geologists familiar with regional ground conditions, to provide impartial advice about the impact of climate change on fragile environments vulnerable to flooding, landslides, melting permafrost and other potential geological hazards. Plus, enhancing water supply management, natural resources, radioactive waste disposal, carbon capture and storage, and planning new developments and infrastructure like their futuristic trans-alpine railway tunnels.</p>","PeriodicalId":100581,"journal":{"name":"Geology Today","volume":"38 4","pages":"147-155"},"PeriodicalIF":0.0,"publicationDate":"2022-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91277013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}