Geoheritage values of one of the largest maar craters in the Arabian Peninsula: the Al Wahbah Crater and other volcanoes (Harrat Kishb, Saudi Arabia)

Al Wahbah Crater is one of the largest and deepest Quaternary maar craters in the Arabian Peninsula. It is NW-SE-elongated, ～2.3 km wide, ～250 m deep and surrounded by an irregular near-perpendicular crater wall cut deeply into the Proterozoic diorite basement. Very few scientific studies have been conducted on this unique site, especially in respect to understanding the associated volcanic eruption processes. Al Wahbah and adjacent large explosion craters are currently a research subject in an international project, Volcanic Risk in Saudi Arabia (VORiSA). The focus of VORiSA is to characterise the volcanic hazards and eruption mechanisms of the vast volcanic fields in Western Saudi Arabia, while also defining the unique volcanic features of this region for use in future geoconservation, geoeducation and geotourism projects. Al Wahbah is inferred to be a maar crater that formed due to an explosive interaction of magma and water. The crater is surrounded by a tephra ring that consists predominantly of base surge deposits accumulated over a pre-maar scoria cone and underlying multiple lava flow units. The tephra ring acted as an obstacle against younger lava flows that were diverted along the margin of the tephra ring creating unique lava flow surface textures that recorded inflation and deflation processes along the margin of the post-maar lava flow. Al Wahbah is a unique geological feature that is not only a dramatic landform but also a site that can promote our understanding of complex phreatomagmatic monogenetic volcanism. The complex geological features perfectly preserved at Al Wahbah makes this site as an excellent geotope and a potential centre of geoeducation programs that could lead to the establishment of a geopark in the broader area at the Kishb Volcanic Field.     

Al Wahbah volcanic explosion crater, Saudi Arabia

Al Wahbah, on Harrat Kishb, is the most spectacular of several volcanic explosion craters found on the lava fields of western Saudi Arabia. A Quaternary phreatic event drilled out a crater 2 km in diameter through Proterozoic basement rocks and Quaternary lava flows. The crater is rimmed with a tuff ring of debris from the explosion, around which were diverted Holocene basaltic lavas.     

五大连池世界地质公园中“火山弹”与“喷气锥”景点定名商榷

位于中国东北黑龙江省的五大连池世界地质公园是世界上著名的自然景点,其引人之处就是新生代玄武岩火山地貌。然而,景点中有些火山构造的命名却存在着明显的错误,如：熔岩丘和增生熔岩球分别被错误地命名为“喷气锥”和“火山弹”。笔者根据著名专业网站（如：美国地质调查局网站）和经典教材中的相应定义讨论了这些火山构造。通过分析这些构造的形态、大小和成因,笔者将它们分别重新命名为熔岩丘和增生熔岩球。笔者建议：地质公园中所有景点的定名都应该经专家核实和评价,从而给出科学的、符合地质实际的名称。     

William Archibald Macfadyen (1893–1985): the ‘father of geoconservation’?

The profile of geoconservation is now higher than ever before with a significant number of people employed worldwide within geoconservation or having an element of it included within their role. Sixty years ago, employment within geoconservation, and even geoconservation itself, were largely unheard of. In 1950, an experienced geologist in his late 50s, William Archibald Macfadyen, ‘Macfadyen’ or ‘Mac’ to his colleagues, became the first full-time professional geoconservationist. After serving in two World Wars and enjoying a long career working as a geologist and hydrogeologist in the Middle East and Africa, he was employed by the newly created government conservation agency in Great Britain, the Nature Conservancy. His role was to help implement new national nature conservation legislation that included the conservation of geological and geomorphological features. Between 1950 and 1960, Macfadyen pioneered geoconservation, working to interpret and implement the new legislation to protect a series of geological and geomorphological sites across Great Britain. Working largely alone he visited, and scheduled for protection, a series of well over 600 sites, developed records to support their conservation, addressed practical conservation issues relating to site damage and enhancement, established a geological advisory committee to support his work, published an account of some of the sites protected and successfully applied his geological expertise to wider issues relating to wildlife conservation. He undoubtedly built the foundations of geoconservation in Great Britain, and in doing so influenced its development worldwide. It is argued here that Macfadyen is worthy of recognition as the ‘father of geoconservation’.     

香港国家地质公园粮船湾组火山岩岩石学研究

在香港国家地质公园西贡火山岩园区,核心地质景观是白垩纪粮船湾组(Kkh)火山岩优美的六方形石柱(柱状节理),它们的岩石类型长期存在熔岩和火山碎屑岩之争。笔者等经野外调查和薄片岩石学研究,确认粮船湾组火山岩实属一种特殊的熔岩——流纹质碎斑熔岩,以普遍的柱状节理、斑晶具有碎斑结构和珠边结构、基质发育霏细结构和流动构造为特征;它们不仅代表了香港地区中生代最晚期火山喷发的产物,而且构成了西贡破火山机构的中央侵出相岩穹。推断粮船湾组火山岩石柱是地球上已知面积最大的流纹质碎斑熔岩石柱群(～150 km2),目前所见的火山岩石柱仅是长期剥蚀后的残余部分。     

Opaque Mineralogy as a Tracer of Magmatic History of Volcanic Rocks:an Example from the Neogene-Quaternary Harrat Rahat Intercontinental Volcanic Field, North Western Saudi Arabia

The Neogene-Quaternary Harrat Rahat volcanic field is part of the major intercontinental Harrat fields in western Saudi Arabia.It comprises lava flows of olivine basalt and hawaiite,in addition to mugearite,benmorite,and trachyte that occur mainly as domes,tuff cones and lava flows.Based on opaque mineralogy and mineral chemistry,the Harrat Rahat volcanic varieties are distinguished into Group I(olivine basalt and hawaiite) and Group II(mugearite,benmorite and trachyte).The maximum forsterite content(~85) is encountered in zoned forsteritic olivine of Group I,whereas olivine of Group II is characterized by intermediate(Fo=50),fayalitic(Fo=25) and pure fayalite in the mugearite,benmorite and trachyte,respectively.The more evolved varieties of Group II contain minerals that show enrichment of Fe2+,Mn2+and Na+that indicates normal fractional crystallization.The common occurrence of coarse apatite with titanomagnetite in the benmorite indicates that P5+becomes saturated in this rock variety and drops again in trachyte.Cr-spinel is recorded in Group I varieties only and the Cr#(0.5) suggests lherzolite as a possible restite of the Harrat Rahat volcanics.The plots of Cr# vs.the forsterite content(Fo) suggest two distinct trends,which are typical of mixing of two basaltic magmas of different sources and different degrees of partial melting.The bimodality of Harrat Rahat Cr-spinel suggests possible derivation from recycled MORB slab in the mantle as indicated by the presence of high-Al spinel.It is believed that the subcontinental lithospheric mantle was modified by pervious subduction process and played the leading role in the genesis of the Harrat Rahat intraplate volcanics.The trachytes of the Harrat Rahat volcanic field were formed most probably by melting of a lower crust at the mantle-crust boundary.The increase in fO2 causes a decrease in Cr2 O3,and Al2 O3,and a strong increase in the proportion of Fe3+and Mg# of spinel crystallizing from the basaltic melt at T ~1200°C.The olivine-pyroxene and olivine-spinel geothermometers yielded equilibrium temperature in the range of 935-1025°C,whereas the range of <500-850°C from single-pyroxene thermometry indicates either post crystallization reequilibrium of the clinopyroxene,or the mineral is xenocrystic and re-equilibrated in a cooling basaltic magma.     

Geotourism,geoconservation, and geodiversity along the belt and road: A case study of Dunhuang UNESCO Global Geopark in China

Dunhuang UNESCO Global Geopark (DHGG) is rich in geoheritage and contains scientific value for studying the sedimentation environments and paleoclimates of Western China. The Geopark is also notable for its aesthetic, cultural, artistic, and recreational value for tourism development. Since geographer Sven Hedin’s discovery of a yardang landform around Lop Nur in 1903, the area has been heavily studied. After the site was designated a National Geopark, geoconservation and geotourism began to rapidly develop and problems associated with these changes emerged. This study characterizes some of DHGG’s typical geoheritage, existing geoconservation, launched geotourism, and also describes some of the area’s challenges. In addition, the opportunities and challenges of DHGG arising from the construction of the Silk Road Economic Belt and 21st-Century Maritime Silk Road (B&R) are discussed. To benefit the sustainable development of DHGG, it is prudent to continue promoting geodiversity, geoconservation, and geotourism by making use of the advantages brought by the B&R.     

江苏扬州旅游地学资源初探

扬州旅游地学资源类型丰富,特色分明,自然性保存好,旅游市场潜力大,在国内具有一定代表性。主要包括火山地貌景观、地层剖面、古生物化石产地与古文化遗址、观赏石、矿产、水体景观、地质工程景观和地质灾害遗迹资源8大类。其中尤以新生代地质火山石柱林、雨花石和龙虬庄古文化遗址为代表,积极地保护与合理的开发利用这些资源,为地方经济和社会发展作出贡献。     

The geology of the 2nd century A.D. Amphitheater Area of Catania,Italy: Historical Eruptions Affecting the Urban District

The amphitheater of Catania is one of the main architectural structures built during Roman domination of the town. It was constructed in two successive phases between the 1st and 2nd centuries A.D. and fell into disuse from the second half of the 4th century. Detailed geological and petrographic investigations allow better geomorphological reconstruction of the area where the monument was built. In particular, the western and eastern portions of the amphitheater are built on prehistoric lava flows, named Barriera del Bosco and Larmisi, respectively. We infer that the choice of site to build the monument was highly influenced by the morphological setting of the area. In fact, the location at the contact between two lava flow fields facilitated excavation and removal of rocks due to the incoherence of the scoriaceous lateral border of the lava flows. Integrating both archaeological and geological data has revealed that a large number of Neolithic, Greek, and Roman sites are located in the lava fields of Barriera del Bosco and Larmisi within the present urban district of Catania, indicating that during its long history the city was directly impacted by only one lava flow, namely in A.D. 1669.     

Geoconservation for science and society: challenges and opportunities

Well managed and accessible geological and geomorphological sites are important to both science and society, for research, education, and, in some cases, for recreation. In this viewpoint paper we celebrate achievements in the field of geoconservation over the last 60 years since the first geological Sites of Special Scientific Interest were designated in the UK following the passing of the National Parks and Access to the Countryside Act in 1949. With a range of new political, social, economic and environmental challenges and opportunities coming to the fore, geoconservation now needs to innovate and adapt in order to sustain and enhance its influence and effectiveness. In advance of the 2011 Geologists’ Association Annual Meeting, Geoconservation for Science and Society: An Agenda for the 21st Century, we give our view on the challenges and opportunities facing geoconservation and the areas in which new approaches and partnerships are required to secure the long-term conservation of our geological and geomorphological heritage.     

四川雷波马湖地质公园景观资源

马湖地质公园以高山湖泊景观为主,马湖湖岸呈锯齿状,水域面积7.32 km2,为我国已知的第四大深水湖泊。此外还有岩溶洞穴、丹霞地貌、火山熔岩、金沙江峡谷地貌、三国文化遗址景观——孟获庙。构成了地质遗迹景观成因类型多样、组合独特、功能齐全、互补性强的综合性景观。该地质公园,具有重要的科考价值、美学价值、观赏价值和保护价值。     

地质景观的素描初探

为了推广地质景观素描在地质公园的应用,提升地学旅游品味与质量,本文以素描为例,对地质景观的艺术展示技术进行了探讨,介绍了地质景观素描的特点及其与传统地质素描的区别。按照所绘制景观形态的不同对地质景观素描进行了分类,系统阐述了地质景观素描的绘制原理和方法,并以敦煌雅丹地貌为例展示了地质景观素描的具体绘图步骤与技巧。地质景观素描是对具有观赏价值和科学价值的地质遗迹景观的绘制,既注重表达地质景观深层的科学内涵,又注重艺术性与生动性。此外,本文就地质景观素描在地质公园中的应用也进行了讨论,主要包括地质公园推广宣传、地质公园解说牌、地质公园纪念品、地质公园网站以及地学科普,并针对这些应用提出了相应的建议。     

The Harrat Al-Birk basalts in southwest Saudi Arabia: characteristic alkali mafic magmatism related to Red Sea rifting

Harrat Al-Birk volcanics are products of the Red Sea rift in southwest Saudi Arabia that started in the Tertiary and reached its climax at ~5 Ma. This volcanic field is almost monotonous and is dominated by basalts that include mafic–ultramafic mantle xenoliths (gabbro, websterite, and garnet-clinopyroxenite). The present work presents the first detailed petrographic and geochemical notes about the basalts. They comprise vesicular basalt, porphyritic basalt, and flow-textured basalt, in addition to red and black scoria. Geochemically, the volcanic rock varieties of the Harrat Al-Birk are low- to medium-Ti, sodic-alkaline olivine basalts with an enriched oceanic island signature but extruded in a within-plate environment. There is evidence of formation by partial melting with a sort of crystal fractionation dominated by clinopyroxene and Fe–Ti oxides. The latter have abundant titanomagnetite and lesser ilmenite. There is a remarkable enrichment of light rare earth elements and depletion in Ba, Th and K, Ta, and Ti. The geochemical data in this work suggest Harrat Al-Birk basalts represent products of water-saturated melt that was silica undersaturated. This melt was brought to the surface through partial melting of asthenospheric upper mantle that produced enriched oceanic island basalts. Such partial melting is the result of subducted continental mantle lithosphere with considerable mantle metasomatism of subducted oceanic lithosphere that might contain hydrous phases in its peridotites. The fractional crystallization process was controlled by significant separation of clinopyroxene followed by amphiboles and Fe–Ti oxides, particularly ilmenite. Accordingly, the Harrat Al-Birk alkali basalts underwent crystal fractionation that is completely absent in the exotic mantle xenoliths (e.g. Nemeth et al. in The Pleistocene Jabal Akwa Al Yamaniah maar/tuff ring-scoria cone complex as an analogy for future phreatomagmatic to magmatic explosive eruption scenarios in the Jizan Region, SW Saudi Arabia 2014).     

Protected areas in Saudi Arabia: Sustainable use of natural resources

The present paper reviews the conservation movement in Saudi Arabia as measured against the established protected areas, as well as the basic philosophy regarding natural resource management. The degree of representation of the biophysical diversity of Saudi Arabia in the established protected areas is discussed by using three areas as case studies: Harrat Al-Harrah (lava field), Urug Bani Mu'arid (Cuesta and Sand), and Raydah Escarpment (High Mountain).     

40Ar/39Ar geochronology of the Neogene-Quaternary Harrat Al-Madinah intercontinental volcanic field,Saudi Arabia: Implications for duration and migration of volcanic activity

New ⁴⁰Ar/³⁹Ar ages, based on incremental heating techniques for groundmass separates of 25 samples, are presented for the Harrat Al-Madinah volcanic field, part of Harrat Rahat in the north western part of the Arabian plate. This area is an active volcanic field characterized by the occurrence of two historical eruptions approximately in 641 and 1256 AD. Field investigations of the main volcanic landforms indicate dominantly monogenetic strombolian eruptions, in addition to local more explosive eruptions. The lavas consist mainly of olivine basalt and hawaiite flows with minor evolved rocks of mugearite, benmoreite, and trachyte that occur mainly as domes, tuff cones and occasionally as lava flows. Previous K/Ar dating shows that the Harrat Al-Madinah lava flows and associated domes comprise seven units spanning an age range of ca. 1.7 Ma–Recent. The new ⁴⁰Ar/³⁹Ar age determinations confirm, to a great extent, the previously obtained K/Ar ages in the sense that no major systematic biases were found in the general stratigraphy of the different flow units. However, the ⁴⁰Ar/³⁹Ar plateau ages show that volcanism in this area began in the Neogene (∼10 Ma) and continued to Recent, with the most voluminous eruptions occurring in the Quaternary. Neogene volcanism occurred in at least three pulses around 10, 5 and 2 Ma, whereas Quaternary volcanism produced at least seven units reflecting lava flow emplacement in the time period of 1.90 Ma–Recent. Thus, the whole duration of volcanic activity in the Harrat Al-Madinah (10 Ma–Recent) appears much longer than that previously identified. The longevity of volcanism in the same part of the moving Arabian plate and absence of evidence for uni-directional migration of volcanic activity indicate that there is no fixed plume beneath this region. The NNW-trending distribution of the volcanic vents is parallel to the Red Sea, and suggests their origin is related to periodic extensional episodes along the reactivated Red Sea fault system.     

黔东南苗岭国家地质公园的旅游地质景观特征和类型

在对贵州黔东南苗岭国家地质公园区的旅游地质景观实地调查研究的基础上,指出其旅游地质景观类型具有观赏与休闲性、奇异与独特性、多样性、古老性、科学性、不可再生性和文化特性;其类型有地层剖面大类、地质构造大类、生物化石大类、地貌景观大类、水体景观大类、环境地质遗迹景观大类和其他旅游地质景观。其丰富多彩的旅游地质景观为旅游开发提供了物质基础,旅游开发潜力大。     

The Parallel Roads of Glen Roy,Scotland: geoconservation history and challenges

Glen Roy is a classic geosite for ice-dammed lake shorelines, the Parallel Roads, and associated features formed during the Loch Lomond (Younger Dryas) Stade (12.9–11.7 ka). The area played a key part in the development of the glacial theory in the early 19th century and continues today to have outstanding scientific value for understanding the processes and timing of events at the end of the last glaciation. Glen Roy has also been long-appreciated as an awe-inspiring visitor attraction, and is now a flagship site for geotourism within Lochaber Geopark. Statutory geoconservation in Glen Roy, beginning in the second half of the 20th century, was founded on the exceptional scientific value of the area. The history and practice of geoconservation in Glen Roy illustrate the contested values of geoheritage and the evolving approaches adopted. Important lessons include the need for open dialogue and partnership working among the local community, land owners and managers, the statutory conservation agency (Scottish Natural Heritage), Lochaber Geopark and the scientific community.     

Pinched between the plates: Armenia's voluminous record of volcanic activity

Located in the heart of the Lesser Caucasus mountains, where the Arabian and Eurasian tectonic plates collide, Armenia occupies an exceptional geological position shaped through millions of years of subduction and collision. It is a unique place on the Earth recording extensive intrusive and volcanic activity related to the long-standing continental convergence. The volcanoes of Armenia provide a rare opportunity to study the sources and processes involved in this unusual type of magmatism. More than 500 Quaternary volcanoes have been mapped in Armenia, most of them formed from single eruptive episodes. Among several large composite volcanoes, the mighty Aragats stands out as the largest volcano in Armenia and the region altogether. Volcanic deposits testify to the range of eruptive styles—from the ignimbrites formed in eruptions as explosive and voluminous as any seen globally in the modern era to the enormous fissure-fed lava flows that form the Southern Caucasus flood basalt province, the smallest and youngest Large Igneous Province in the world. Several pre-historical and historical eruptions have been documented, highlighting the potential for future volcanic activity in the region. In recent years, research has focused on the volcanic hazards associated with the Armenian Nuclear Power Plant, located in the foothills of Aragats volcano. This article highlights some of the extraordinary volcanic and intrusive features observed in Armenia and summarizes aspects of recent volcanological and petrological research.     

Aeromagnetic data over Harrat Lunayyir and surrounding areas,western Saudi Arabia

Harrat Lunayyir is one of the smaller lava fields in western Saudi Arabia that is of current interest due to a dike intrusion episode in 2009, an ongoing swarm of earthquakes and the possible hazard that pose. In addition to seismology, other geophysical data have been used to study the structure of the area, and the available aeromagnetic information is shown and discussed here. The reduced to the pole (RTP) magnetic grid and its enhancements have been used to define some of the main anomalies, and these have been correlated with the known geology, including the Red Sea coastal dike system. There are numerous linear features that are possibly related to the dikes or faulting, but within the area of the harrat, details due to the underlying structure are largely obscured by the magnetic surface lavas. Northeasterly trends in the magnetic data may indicate old zones of weakness that intersect one of the main coastal dikes at the location of the recent seismic activity and surface fissure, suggesting that this is a point of weakness resulting in the volcanism and seismicity that also appears to be largely limited to two of the NE trends. The association of the recent seismicity with a known geological and aeromagnetic feature is important in determining the seismic hazard for the region, especially if the location of future activity can be used to reduce overall uncertainty in the analysis by identifying potential fault sources. Here, the seismicity appears to lie on one of the NNW-trending coastal dikes that have been reactivated recently along a section between two NE-trending older faults.     

安徽“两山一湖”地区地质遗迹资源评价

安徽省“两山一湖”地区地质遗迹资源十分丰富,有层型剖面和极为丰富的古生物化石,有斜贯皖南中部台地的斜坡相沉积,还有极其丰富的构造形迹、岩溶、洞穴、温泉、瀑布、古火山、古冰川等地质景观。其中以黄山、九华山为代表的花岗岩地貌景观、以齐云山为代表的丹霞地貌景观、以清凉峰为代表的火山岩地貌景观和歙县鸡母山侏罗纪恐龙化石最具代表性。通过对区内地质遗迹的分类探讨,叙述了地质遗迹的内容,对区内地质遗迹的开发现状及存在的问题进行了阐述,对地质自然景观资源的开发潜力及开发价值进行了评述。