Abstract Sir Archibald Geikie (1835–1924), one of the towering figures in the history of British geology, maintained a long professional relationship and correspondence with pioneering American geologists of the nineteenth century, including James Dwight Dana, Clarence Dutton, Ferdinand Vandeveer Hayden and Grove Karl Gilbert. Geikie made two trips to the USA. Geikie’s first trip, accompanied by his former student at Edinburgh Henry Drummond, took place in August–November 1879 for field excursions in the American ‘Far West’, including Colorado, Utah, Wyoming, Idaho and Montana, where he could find ample evidence for the dominant role of fluvial erosion in the denudation of continents (a school of thought called ‘fluvialism’ or ‘erosionalism’). These geological excursions also resulted in nine articles by Geikie published during 1880–82 as well as a large number of landscape paintings and sketches now preserved at the Haslemere Educational Museum in England. Geikie’s second trip from April to May 1897 was due to an invitation to deliver a series of lectures on ‘The Founders of Geology’ at Johns Hopkins University; these lectures became the basis for his classic book of the same title. Geikie kept an active interest in geological mapping and discoveries in the USA, as evident from his numerous references to American geology in his 1882 Text-book of Geology . Geikie’s American connections demonstrate that geology, although primarily a field-based regional science, did not evolve in isolation in various countries during the nineteenth century, but that there was lively exchange and synergy in geological research and findings among geologists working in Europe, the Americas and Asia.

Abstract The history of the European oil and gas industry reflects local and global political events, economic constraints, and the personal endeavours of individual petroleum geoscientists, as much as it does the development of technologies and the underlying geology of the region. Europe and Europeans played a disproportionately large role in the development of the modern global oil and gas industry. From at least the Iron Age until the 1850s, the use of oil in Europe was limited, and the oil was obtained almost exclusively from surface seeps and mine workings. The use of oil increased in the 1860s with the introduction of new technologies in both production and refining. Shale oil was distilled on a commercial scale in various parts of Europe in the late eighteenth century and throughout the nineteenth century but, in the second half of the nineteenth century, the mineral oils and gas produced primarily from shale and coal could no longer satisfy demand, and oil produced directly from conventional oil fields began to dominate the European market. The first commercial oil wells in Europe were manually dug in Poland in 1853, Romania in 1857, Germany in 1859 and Italy in 1860, before the gradual introduction of mechanical cable drilling rigs started in the early 1860s. In the late nineteenth century, the northern part of the Carpathian Mountains in what is now Poland and Ukraine was one of the most prolific hydrocarbon provinces in the world. The Bóbrka Field in the Carpathian foothills of Poland, discovered in 1853, is still producing and is now the oldest industrial oil field in the world. The 1914–18 and 1939–45 world wars were both major drivers in exploration for and exploitation of Europe’s oil resources and in the development of technologies to produce synthetic fuels from the liquefaction of bituminous coal and the combination of carbon monoxide and hydrogen as the Allied and Axis governments struggled to maintain adequate supplies of fuel for their war efforts. In Britain, the first ‘accidental’ discovery of gas was made in 1875 in the Weald Basin, but it was not until 1919 that Britain’s first oil field was discovered at Hardstoft, in Derbyshire, as a result of a government-funded exploration drilling campaign, triggered by the need to find indigenous supplies of oil during World War I. The period of reconstruction after World War II was also critical for the European oil and gas industry with further successful exploration for oil and gas in the East Midlands of England resulting in Britain’s first ‘oil boom’, and the discovery and development of deep gas fields in the Po Valley in northern Italy fuelling the Italian economy for the next 50 years. Drilling technologies developed during Britain’s first oil boom, together with the extrapolation of the onshore geology of the East Midlands oil fields and of the Dutch gas fields, led to the discovery of the huge oil and gas resources beneath the North Sea in the 1960s and 1970s, which enabled Britain, Norway, Denmark and The Netherlands to be largely self-sufficient in oil and gas from the late 1970s until production began to decline rapidly in the early 2000s. Today, oil and gas production in most European countries is at an historical low. Exploration for new sources of oil and gas in Europe continues, although increasingly hampered by the maturity of many of the conventional oil and gas plays, but European companies and European citizens continue to play a major role in the global oil and gas industry.

Abstract Sir Thomas Boverton Redwood (1846–1919) stands as a giant in the history of petroleum science and technology. This paper pieces together scattered information about his life and work, and discusses his contributions, directly or indirectly, to petroleum exploration and production in various parts of the world, especially Burma (Myanmar), Persia, Mexico and the West Indies with which British colonial and commercial interests were related. Redwood established one of the first and most successful consulting firms for petroleum companies, and, in this way, trained generations of petroleum geologists and engineers. His masterpiece, Petroleum: A Treatise , which went through five editions from 1896 to 1926, summed up the knowledge of petroleum of its age, and still remains a valuable book for historical reference. Redwood’s mediatory position between scientific, industrial and political circles in Britain enabled him to play a leading role in the development of petroleum technology, as well as Britain’s oil operations around the world during the 1880s–1910s. He served as a technical advisor to many government committees and oil companies, and his total dedication to Britain’s oil security during World War I and during the transformation of the Royal Navy’s fleet from coal to oil fuel were the climax of his professional life.

The whole southern border of Eurasia advances in a series of great folds towards Indo-Africa; these folds lie side by side in closely syntactic arcs, and for long distances they are overthrust to the south against the Indo-African table-land… This circumstance distinctly indicates that the folding of the uppermost part of the Earth’s mass is, under certain conditions, only the expression of a forced adaptation… A great part of this folding is of recent age, or has been continued into very recent times; it is not certain that the movement has ended. —Eduard Suess (1904), The Face of the Earth , vol. 1, p. 596–597

ABSTRACT This is an in-depth review and analysis of the long and untold history of development of earth science, geological thinking, research, and exploration on the Iranian Plateau within its historical, political, and socioeconomic context. Widespread mineral resources and ancient civilization helped in exploration, excavation, smelting, and usage of different metals, precious stones, and minerals since the Neolithic Period. Extant ancient Avestan and Middle Iranian Pahlavi Zoroastrian texts, as well as the classic Greek and Roman scholars, clearly demonstrate the Iranian geological activity through the Median (ca. 615 BCE), Achaemenid (550–330 BCE), Parthian (250 BCE–224 CE), and Sassanid (224–642 CE) Dynasties, interrupted by disrupting periods of socioeconomic and political problems, followed by foreign invasions and devastation in 330 BCE–250 CE and 637–652 CE, when the Iranians could no longer make scientific advancements. Long after the invasion of Alexander III of Macedon (330 BCE), scientific activity culminated in the establishment of the academies of Gundishāpur, Ctesiphon, and Resaina, the three higher educational centers of the Sassanid Dynasty that focused on comprehensive observation, painstaking research, and advanced education during the sixth and seventh centuries CE. Careful observation, research, and experiment by brilliant and genius scholars such as Karaji, Biruni, and Avicenna took place during a period of great activity and growth in science, engineering, medicine, literature, art, architecture, and philosophy in the tenth and eleventh centuries CE in Iran. This Iranian two-century “intermezzo intellectual zenith,” with a stable state and economic prosperity, was nurtured by the vast heritage of the ancient Iranian, Mesopotamian, Indian, and Egyptian civilizations and elements of the ancient Avestan, Sanskrit, and Pahlavi writings since ca. 1200 BCE. Social, economic, and political conflicts followed by invasions by Central Asian nomadic tribe warlords and their accompanying hordes in 1000–1040 CE (Saljuqs), 1218–1231 CE, and 1256 CE (Mongols), and 1370 CE (Timurids), and their occupation caused the process of irreversible decay, retrogression, and general intellectual decadence until the Safavids (1491–1772 CE). During this relatively long dark period, there was a drastic decline in interest in geological research and writing, though some old mining efforts were active. Throughout the eighteenth to the mid-twentieth centuries, foreign travelers made some contributions to the geology and mineral resources of Iran. It was during the second half of the twentieth century when once again earth science research blossomed in Iran with the help of European geologists. This ushered in a new period of modern geologic studies of Iran by native geologists. In memory of Emil Tietze (1845–1931), Alexander von Stahl (b. 1850), Setrāk Ābdāliān ( 1894–1963), Eugène Rieben (1899–1972), Heinrich Martin Huber (1917–1992), Jovan Stöcklin ( 1921–2008), Ricardo Assereto (1939–1976), and all pioneers in the past, who enthusiastically and rigorously intruded ever deeper into virtually unexplored territories in difficult and uncomfortable circumstances, extremely devoted to scientific pursuits, and shaped our understanding of the geology, tectonics, mineral resources, earthquakes, and seismotectonics of the Iranian Plateau .

ABSTRACT The megacity of Tehran, the political, economic, and military center of Iran, is exposed to a risk of large-magnitude earthquakes originating on several adjacent and inner-city active faults. The city lies at the southern foot of the central Alborz Mountains, which frame the South Caspian Basin and have been the source of damaging historical left-lateral strike-slip and reverse-fault earthquakes. The most recent destructive earthquake in Alborz was the Rudbār left-slip earthquake of M w 7.3 on 20 June 1990 northwest of Tehran, taking more than 40,000 lives and destroying three cities. This earthquake was in a seismic gap, and its source fault did not show clear geomorphic signs of being active prior to the earthquake. East of Tehran, the 22 December 856 Komesh (Dāmghān) earthquake had a magnitude previously estimated at M s 7.9, with estimated losses of 40,000–200,000 lives. Our reevaluation of historical, archaeological, and structural evidence reduces estimates of both magnitude and losses, similar to the 1990 Rudbār earthquake. The latest earthquake to affect the present Tehran metropolitan area was the Lavāsānāt earthquake on the central section of the Moshā fault, on 27 March 1830, with its epicenter located ~30 km northeast of the city, which had a magnitude of M w ~7.0–7.4. Prior to this event, the Ruyān earthquake north of Tehran struck the same section of the fault on 23 February 958, with a magnitude previously estimated as M s 7.7, although our reevaluation reduces the magnitude to around M w ≥7.0 (7.0−7.4). Both the 958 and 1830 earthquakes along the central segment of the Moshā fault, with an interval of 872 yr, might have loaded the North Tehran fault system near the cities of Tehran and Karaj, as well as the faults underneath the metropolitan area. The North Tehran fault system west of Tehran might have sustained an earthquake of M w ~7.0 in May 1177. The earthquake histories of the Niāvarān, Darakeh, Farahzād, and Kan left-lateral strike-slip faults (part of the North Tehran fault system at the mountain front north of the city), the inner-city Mahmudieh and Dāvudieh south-dipping reverse faults, the central-eastern section of the North Tehran fault system (now within the metropolitan area) as well as blind thrusts under the city are unknown. Except for the 1830 distant earthquake, no medium-to large-magnitude earthquake (M w 6.5–7.5) has occurred within the Tehran metropolitan area during the past 839 yr along the faults beneath the metropolitan area or in the immediate vicinity. This may indicate a >839-yr-long period of strain accumulation within a long interseismic period between large-magnitude earthquakes in Tehran. With the active-fault hazard to the rapidly growing population along several faults, it is necessary for the government to: (1) conduct extensive paleoseismic trenching to identify the most hazardous of Tehran’s faults, previous rupture areas, average coseismic slip rates, earthquake magnitudes, and average recurrence periods of earthquakes from at least eight fault systems within the metropolitan area; (2) deal with extensive corruption of the construction and building-inspection industries; and (3) enforce the 1969, 1988, and 1999 Iranian Code for Seismic Resistant Design of Buildings. As with the 12 January 2010, M w 7.0 Haiti earthquake, losses from the next Tehran earthquake of M w ≥7.0 could exceed 100,000 people. It is necessary to prepare and implement an earthquake management master plan as a disaster prevention tool, enforce the building code with transparency, and retrofit public structures and infrastructure in order to mitigate earthquake risk in Tehran and protect the lives of ~15 million people (roughly 20% of the country’s population) living in the Tehran and Alborz (Karaj city) Provinces. Considering the continuous threat of earthquake hazard in Tehran and the suburbs, we should immediately prepare the necessary plans to mitigate the earthquake risk by utilizing the scientific and engineering techniques derived from earth sciences; we should do this before an earthquake strikes. —Professor Setrāk Ābdāliān, 1951, Tehran (translated from Persian)

ABSTRACT We present the first critical examination of the > 1300 yr history of the Borujerd old congregational mosque by means of scrutinizing ancient historical chronicles, archaeology, architecture, historical and modern seismicity, geology, and regional active faults. Our study resulted in recognition of at least four major phases of destruction, rebuilding, and renovations of the megastructure located 4 km to the northeast of the Zagros Main Recent fault in western Iran. The grand structure shows significant paleo-architectural and archaeological evidence of destruction and damage. Although some damage events, recorded in seven phases since the seventh century C.E., could have been due to the poor construction of early periods and their decay, there is strong evidence of at least one extensive, simultaneous, and abrupt destruction and damage pattern of mosque III (ca. post–1090/pre–1139 C.E.) in the early fourteenth century. We suggest that the poorly known 1316 C.E. strong earthquake (which destroyed more than 20 villages in the general area, with erroneous epicentral location in the historical seismic catalogues) was possibly responsible for the simultaneous sudden collapse of the Borujerd congregational mosque lofty dome chamber and its tall free-standing minaret; we infer that this earthquake occurred with intensity > VIII + (modified Mercalli intensity scale) conceivably along a seismic gap zone of the Zagros Main Recent fault. No pre–1316 C.E. monument exists in the epicentral region, and no strong earthquake has occurred along that segment of the Zāgros Main Recent fault for the last seven centuries. Retrospectively, apparent indigenous paleo-architectural renovations were utilized during construction of the new congregational mosque (mosque IV: ca. post–1405/pre–1447 C.E.) to enhance the coherency and elasticity of the rigid brick structure to withstand future earthquake shear stress. The hazard-reducing efforts included: (1) retrofitting the surviving load-bearing structural elements; (2) avoiding grandeur and majesty and implementing simplicity by reducing the size, height, and shape of the dome chamber; (3) avoiding free-standing minarets; (4) minimizing the size and reducing the light/ventilation openings; and (5) utilizing several levels of timber bracings to neutralize earthquake strong ground motion. Our research reveals that the return period of large-magnitude earthquakes along the two major segments of the fault is in the range of 1000 and 2000 yr, thus making historical earthquakes unrecognizable through routine historical research. It also shows how the use of archaeoseismology and paleo-architectural investigations on deformed monuments may improve our knowledge of long-term seismicity and seismic hazards of a region. This kind of study permits us to hypothesize the occurrence of strong earthquakes in an area for which historical seismicity does not show significant earthquakes. Finally, based on the described historic seismic damage and destruction, the regional national monuments should be properly retrofitted to withstand future earthquake hazards.

ABSTRACT A significant part of the convergence between the Iranian and Arabian plates since the late Cenozoic has been accommodated by several strike-slip faults, especially in the eastern and central areas of Iran. The Great Kavir fault is one of the cases in which there is little consensus regarding its kinematics, mechanism of development, and tectonic history, mainly due to a lack of detailed studies. Field and satellite image studies of the Pees Kuh Complex, a well-preserved Cenozoic structure that developed upon the Great Kavir fault near Jandaq, in central Iran, suggest a virtually perfect, positive-flower structure. It is argued that the Pees Kuh Complex is the result of a combination of both left strike-slip and reverse dip-slip displacements on the Great Kavir fault. The main structural elements comprising this flower structure are as follows: a Paleogene sedimentary assemblage, composed of an array of thrust faults with NW to EW trends, thrusted upon the Great Kavir block; a few reverse faults with N to NW dips at the southern side of the Great Kavir fault; several synthetic en echelon faults; and a number of antithetic NW-trending en echelon faults. In addition, left-stepping en echelon folds with NW-trending axial planes are recognizable. The Pees Kuh Complex shows a thrust sequence of an upward-verging antiform structure including overturned folds formed of middle to late Eocene marl and sandstone beds. These sheets have a nearly vertical position at their roots, mainly confined to the Great Kavir fault, which changes to a horizontal position further along the fault. Because the thrusts transported middle-late Eocene rocks atop Oligocene-Miocene red beds and are, in turn, covered by Pliocene-age continental beds, the age of the Pees Kuh Complex is inferred to be younger than the Miocene. Considerable left-lateral displacement of the Great Kavir fault in the Jandaq area is confirmed by geometrically measured counterclockwise rotation of ~20° of the faulted blocks around approximately vertical axes relative to the Great Kavir fault in the Godar-e-Siah area. This study, in addition to other previous lithological evidence gathered from the Jandaq area, demonstrates deformation of the Pees Kuh Complex as a reactivation of an older regional fracture, such as a suture zone, as the Paleogene sedimentary rocks were subjected to a different stress field in late Cenozoic times.

ABSTRACT We discuss geochemical, chronological, and field data from the extrusive sequence and individual diabase and sheeted dikes in the Upper Cretaceous Khoy, Kermanshah, Fannuj, Nosratabad, south Fariman, northwest Fariman, Dehshir, and Sabzevar ophiolite massifs of Iran. The extrusive sequences include pillow lava, sheet flow, hyaloclastite, hyaloclastic breccia, and interbeds of chert and pelagic limestone with Late Cretaceous microfauna. The Khoy, northwest Fariman, and Sabzevar massifs also include Upper Cretaceous–Lower Paleocene supra-ophiolitic volcanic and volcanic-sedimentary rocks that formed in a trough near the basin where the extrusive sequence formed. The Khoy pillow lava displays transitional (T) mid-ocean-ridge basalt (MORB) characteristics but no chemical contribution from the components released from the subducted slab. On the other hand, the diabase dikes that cut the Khoy extrusive sequence show signatures of subduction-zone magmatism and contribution from the melt released through the partial melting of the subducted slab. While lava in the Harsin (Kermanshah) extrusive sequence in west Iran displays enriched (E) MORB and plume (P) MORB characteristics, the pillows in the Fannuj, northwest Fariman, Dehshir, and Sabzevar extrusive sequences indicate the contribution of both fluids and melt from the subducted slab. The Nosratabad and south Fariman ophiolites also show evidence for either melt or fluids, respectively. Partial melting of the subducted slab sedimentary cover may have formed the acidic pillow lava and sheet flow in the Fannuj and Nosratabad extrusive sequence, respectively. Some pillows in the Nosratabad, Sabzevar, northwest Fariman, and to a lesser extent, Dehshir extrusive sequence display oceanic-island basalt (OIB) geochemical characteristics. Mantle plumes or asthenospheric flow that probably moved up through weak zones of the subducted slab may have affected the partial melting of the mantle wedge above the slab. The combined OIB and suprasubduction characteristics suggest the role of rollback of the subducted slab in the magmatism of the northeast Iranian ophiolites. The clear MORB-like geochemical characteristics in the extrusive sequence of the ophiolites in northwest and west Iran, and the suprasubduction-zone characteristics in the diabase and extrusive sequence of the ophiolites in southeast and east Iran, west of the Lut block, and northeast Iran may represent a major Late Cretaceous transition from a MORB to a suprasubduction-zone setting.

ABSTRACT The Khoy area in northwest Iran is composed of five major geological units that, from east of Khoy to the Iran-Turkey border, include the southwestern edge of Central Iran, the Eastern metamorphic complex (including its meta-ophiolitic complex), Upper Cretaceous–Lower Paleocene supra-ophiolitic series, an Upper Cretaceous non-metamorphic ophiolite complex, and the Western metamorphic complex. The main objective of this paper is to compare the geology of the Khoy ophiolites in Iran with similar units in neighboring southeast Turkey. The Neoproterozoic m1 basement unit of the Eastern metamorphic complex in Iran was part of a large continental block that also included the basements of the Central Iran microcontinent, the northern margin of Gondwana, and the basement of tectonic units in Turkey. The continental crustal block was split along a rift in northwest Iran–southeast Turkey after the oceanic crust and related suprasubduction series were formed during the Late Triassic–Early Jurassic. The subduction of the eastern margin of the oceanic crust under Central Iran led to the metamorphism of the crust and supra-ophiolitic series to the greenschist-amphibolite facies and formation of Khoy’s Eastern metamorphic complex during the Middle Jurassic–Late Cretaceous. The meta-ophiolitic part of the Eastern metamorphic complex in Iran probably correlates with the Berit mountain meta-ophiolite in the southeast Anatolian region in Turkey. Continued subduction in the east and accretion onto Central Iran led to the injection of Upper Cretaceous– Lower Paleocene granitoid masses. The oceanic crust developed an extensive plutonic sequence and the thickest (>1000 m) extrusive sequence among Khoy ophiolite massifs during the Late Cretaceous. The Upper Cretaceous Khoy ophiolite is nonmetamorphic and can be correlated with the ophiolite massifs in the northern ophiolite belt of the southeast Anatolian region in Turkey, such as Berit (Göksun), İspendere, Kömürhan, and Gulman. The southeast Anatolian ophiolite massifs, however, stand above and below the Bitlis-Engizek metamorphic complexes and represent different tectonic units. In contrast to the ophiolites of the northern belt in the southeast Anatolian region in Turkey, which show suprasubduction geochemical characteristics, the Khoy extrusive sequence displays transitional (T) mid-ocean-ridge basalt (MORB)–like and normal (N) MORB-like patterns, and it is cut by diabase dikes with suprasubduction-zone compositions, indicating a geodynamic transition from a MORB to a suprasubduction setting before the injection of the dikes in the Late Cretaceous–early Paleocene. The Khoy supra-ophiolitic series, which evolved in a trough along the eastern margin of the Late Cretaceous ocean, correlates with the Elaziğ volcano-sedimentary rocks in the southeast Anatolian region in Turkey. The Eocene volcano-sedimentary rocks in the Khoy area can be correlated with the Maden group in Turkey, which has been defined as a volcano-sedimentary succession of middle Eocene age, representing a short-lived back arc basin. Upper Miocene quartz monzodiorite masses with a subduction geochemical signature are the youngest intrusions that cut the supra-ophiolitic series and Upper Cretaceous ophiolitic rocks in Khoy.

ABSTRACT The Sanandaj-Sirjan zone in Iran is a part of the Cimmerian terrane, which was accreted to Eurasia in the Late Triassic. This zone was later incorporated into the Zagros orogen, which resulted from the collision of Eurasia (Iranian subplate) with the northern Gondwana margin (Arabian subplate) during the Cenozoic. Characteristics of different rock units and their stratigraphic relationships combined with evidence from magmatic and metamorphic events in the southern part of the Sanandaj-Sirjan zone, as examined in this paper, resulted in identification of 11 tectono-stratigraphic units that record different tectonic environments involved in the opening and closure of the Neotethys Ocean in southwestern Iran. During Paleozoic intraplate extension, sedimentation and igneous activity took place in aborted rift system to continental shelf settings in the southern part of the Central Iranian Platform (unit 1). Spreading of the Neotethys was associated with formation of Upper Permian (unit 2) and Lower to Middle Triassic turbidites and volcanics (unit 4) in an intracontinental rift setting, which continued up to the Late Triassic. Late Triassic subduction caused the metamorphism of the aborted rift materials (unit 3), calc-alkaline magmatism (unit 5), deposition of a turbiditic sequence and associated volcanic rocks of Early to Middle Jurassic age (unit 6), and carbonate sedimentation during the Early Cretaceous (unit 7). These subduction-related units of Late Triassic–Early Cretaceous age formed respectively in a high-temperature–low-pressure metamorphic regime, magmatic arc, forearc basin, and continental platform. The Zagros suture zone of Late Cretaceous age (unit 8), the Tertiary flysch-type sediments (unit 9), and the Oligocene–Miocene sedimentary succession (unit 10) are tectono-stratigraphic units formed during the Neotethyan obduction to Arabia-Asia continental collision phases. Finally, the young molasse sediments (unit 11) were shed from the postcollisional highlands into intramontane basins. This chapter also proposes the presence of two sutures in southwest Iran: Suture zone I marks the subduction-obduction of Neotethys toward the end of the Cretaceous, while the younger (Eocene–Oligocene) suture zone II marks the closure of the Oman Ocean between suture zone I and the Sanandaj-Sirjan zone.

ABSTRACT The lower–middle Cambrian boundary transition in Iran consists of the upper lower Cambrian Shale and Quartzite units of the Lalun Formation (nearly all siliciclastics) and the overlying lower middle Cambrian Member 1 carbonates (dominantly carbonates) of the Mila Formation, the facies and stratigraphy of which reflect deposition on an extensive ramp platform in the northern passive margin of Gondwana. This paper focuses on facies and sequence stratigraphic analyses of the boundary interval to document the unconformable boundary on the Quartzite unit, which may record the late early Cambrian global Hawke Bay (Toyonian) regression, and to define depositional sequences for regional and global correlation. The Shale unit unconformably overlies the fluvial red beds of the Lalun Sandstone unit. The unconformity is marked by a pebbly chert arenite containing black chert clasts and reworked caliche pisoids in places, and it is coeval with the black chert conglomerate at the base of the Shale unit equivalent in east-central Iran. The Shale unit conformably underlies the Quartzite unit, the base of which is marked by a change in depositional trend, but where no evidence for an unconformity is recognized. This unit includes two reef horizons composed of dolomitized individual and compound metazoan buildups capped by planar to wavy stromatolite. The upper contact of the Quartzite unit marks a regional unconformity and the abrupt appearance of shallow-marine carbonates of the Mila Formation. The unconformity is characterized by a distinctive dark reddish brown- to red-weathering horizon, in which most of the sand grains are altered to a hematitic matrix and the sand content decreases toward the top of the profile. Close to the unconformable boundary, in a short stratigraphic interval (~3 m), an open-marine thrombolite reef zone capped by oolithic limestone is recognized near the base of the Mila Formation. The basal Mila boundary thrombolites, widespread development of stromatolite reefs, oncoids, and ooids, and absence of metazoan reefs in the middle Cambrian Member 1 of the Mila Formation may indicate a stressed ecosystem in the aftermath of the Hawke Bay extinction event and reef crisis similar to basal Triassic deposits. Four depositional sequences (third-order cycles) are recognized in the late early Cambrian–early middle Cambrian interval that are similar to the south China sequences. There is a good correlation between the unconformable boundaries recognized in this study and the major global sea-level falls reported for the late early Cambrian and early middle Cambrian intervals. The unconformity-bounded upper lower Cambrian fluvial red bed succession that overlies the lower Cambrian shallow-marine carbonates signifies the first pause in the Cambrian transgression. It correlates with the major global lowstand at the base of the Toyonian Stage and is here referred to as the early Toyonian Hawke Bay regression. The conspicuous unconformity on the Quartzite unit that underlies the basal transgressive package and the boundary thrombolite reef zone near the base of the Mila Formation indicate a major hiatus that is interpreted to correspond to the culmination of the global late early Cambrian Hawke Bay regression (Sauk I-II unconformity) and the Hawke Bay extinction event. The event resulted in the demise of metazoan reef builders and the emergence of microbialite reefs, oncoid, and ooid facies in the middle Cambrian basal members of the Mila Formation.

ABSTRACT Sixty-four surface samples from the Lower Paleozoic rock units (mainly the Lalun, Abastu, and Abarsaj Formations) near the village of Kholin-Darreh in the Fazel Abad area, southeastern Caspian Sea, northern Iran, were analyzed to determine their age relationships. The samples from the Lalun Formation are barren, but those from the Abastu and Abarsaj Formations contain well-preserved and abundant palynomorph entities, which are dominated by acritarchs (23 species belonging to 15 genera) and chitinozoans (29 species distributed among 15 genera). Scolecodonts and graptolite remains as well as a few cryptospores were also observed, although these were not determined in detail. Based on the restricted stratigraphic range of acritarch species, an Early Ordovician (Tremadocian) age is assigned to the Abastu Formation, while based upon index chitinozoan and acritarch taxa, a Late Ordovician (Katian to Hirnantian) age is assigned to the Abarsaj Formation. Likewise, based on the presence of diagnostic chitinozoan taxa, the Abarsaj Formation can be assigned to the Armoricochitina nigerica, Ancyrochitina merga, Tanuchitina elongate , and Spinachitina oulebsiri chitinozoan biozones. These chitinozoan assemblages reflect a clear paleobiogeographic affinity with the so-called “North Gondwana Domain.” The composition of acritarch assemblages also appears to be consistent with newly proposed hypotheses of a Late Ordovician phytoplanktonic biogeographical differentiation between a Laurentian/Baltica realm and a Gondwanan realm, with the present assemblages belonging to the latter. The presence of some chitinozoan and acritarch taxa from the Baltic and Laurentia in Gondwanan chitinozoan biozones of the Fazel Abad area suggests the existence of counterclockwise marine currents, which brought planktonic organisms (acritarchs, chitinozoans, and graptolites) from lower latitudes (Baltica) to higher latitudes (North Gondwanan Domain) settings. The presence of a low-diversity acritarch assemblage in the Abastu Formation and taxonomically diverse chitinozoan, acritarch, and scolecodont assemblages in the Abarsaj Formation suggests a marine depositional environment for these two formations. Two major hiatuses are present within the studied Lower Paleozoic succession in the Fazel Abad area. The first hiatus appears between the Lalun Formation (Early Cambrian) and the Abastu Formation (Tremadocian) and includes the Middle-Upper Cambrian Mila Formation. The second hiatus occurs between the Abastu Formation (Tremadocian) and the Abarsaj Formation (Katian–Hirnantian) and spans the interval of the Floian-Sandbian, which corresponds to uplift related to the initial stage of rifting of the Paleo-Tethys Ocean.

ABSTRACT We investigated the sequence stratigraphic architecture of Neogene deposits in the Zagros region using 12 measured stratigraphic sections and performing strontium isotope measurements on 10 samples. We combined our data with 44 previous published Sr isotope measurements and five paleomagnetostratigraphic sections in order to place the foreland deposits in a chronostratigraphic framework. Two chronostratigraphic charts were created, and transgressive-regressive system tracts were identified in the western and eastern sectors of the Zagros. These results show that the southward migration of the Zagros fold-and-thrust belt led to broadly upward-coarsening, progradational sequences due to progressive uplift and seaward (south-westward) migration of the Zagros fold-and-thrust belt. In addition, we show distinct differences in the sequences between the eastern and western sectors. It can be inferred that, in the strike-parallel direction, the Zagros foreland basin did not respond in a simple manner to tectonics and global sea-level changes during the Neogene. The different architecture of the sequences and mismatch of Neogene sedimentary architecture with global sea-level curves imply different orogen-parallel evolutionary histories and strong impact of tectonics on the basin evolution as compared to eustasy. Finally, we present evidence for a retrogradational sequence related to a period of enhanced deformation and related crustal thickening during the middle Miocene in the eastern Zagros.

ABSTRACT We investigated 335 landslides (including rockslides, rock avalanches, soil slides, and slides) in the Zagros mountain belt of southwest Iran using a digital elevation model (DEM) with 30 m resolution, Google Earth™ images, and field investigation. Individual landslides have volumes ranging from 10 4 (the lower limit of resolution) to 3 × 10 10 m 3 and cover surface areas ranging from 10 3 to 10 8 m 2 . The relationship between landslide volume ( V L ) and area ( A L ) is well described by a power law of the form V L = A L α , where α = 1.49 over five orders of magnitude of A L and seven orders of magnitude of V L . We also show that the frequency-size (i.e., volume) distribution is heavy tailed, following a power law for the largest landslides (>10 7 m 3 ) with a scaling exponent β = 1.51. Non-power-law behavior for smaller landslides is probably an artifact due to the relatively low resolution of our data, such that we are essentially missing many small landslides. Comparison of these results with the other published data sets around the globe shows that the Zagros landslides are relatively larger, and they show similar scaling behavior to those observed in other regions, especially with regard to data sets where landslides are deep-seated or relatively large and occur in relatively resistant materials (e.g., consolidated rocks, as opposed to soil). In addition, we used principal component analysis (PCA) to investigate links between the size of landslides and causative factors (e.g., geological, geomorphological, and physical factors). Our results highlight that although the size of landslides is not controlled by any single factor, their geographic distribution is strongly influenced by lithology, elevation, and slope.