A Historical Account of the Stratigraphy of Qatar, Middle-East (1816 to 2015) (original) (raw)
Related papers
Biosis: Biological Systems, 2021
The author learned first-hand about the surface stratigraphy and geology of Qatar by dedicating most of his weekends at conducting field works and public guided field tours from 2007 to 2020 while employed by Qatar Petroleum. Here, he reviews and updates the surface stratigraphic knowledge of Qatar since the last lexicon was published back in 1975. The geology and macro-paleontology of the Lower Eocene Rus, Middle Eocene Dammam, Lower Miocene Dam and Mio-Pliocene Hofuf formations are described in detail and well illustrated.
A 3-Day Geological Field Trip in Qatar
BioSis, 2022
The author learned fi rst-hand about the surface stratigraphy and geology of Qatar by dedicating most of his weekends at conducting fi eld works and public guided fi eld tours from 2007 to 2020 while employed by Qatar Petroleum (now QatarEnergy). Here, he summarizes his knowledge of the surface geology of Qatar in a 3-Day fi eld trip designed to provide the participants a hands-on overview of the stratigraphy of the country. The field trip is based on his publication (LeBlanc, 2021) which is an integral part of this geological tour (the participants are referred to it on several occasions) and his other geological publications on Qatar referenced herein (LeBlanc, 2008, 2009, 2014, 2015, 2017, 2019). During this 3-day fi eld trip, outcrops of the Lower Eocene Rus Formation, Middle Eocene Dammam Formation, Lower Miocene Dam Formation, Mio-Pliocene Hofuf Formation, as well as Pleistocene and Holocene deposits will be visited. The fi eldtrip’s aim is to help the participants at recognizing the various formations and their members, as well as the most obvious features (faults, folds, dissolution, mineralization, fossils, etc..) that characterize them.
The Stone Age of Qatar: new investigations, new finds; interim report
Proceedings of the Seminar for Arabian Studies 44: 317-324, 2014
This interim report summarizes the results of fieldwork carried out by the PADMAC Unit during 2012/2013 in a previously unexplored area of southern Qatar. The aim of this series of systematic surveys was to find undiscovered lithic surface-scatters/sites and characterize the assemblages. Prior to fieldwork, a detailed desk-based geospatial analysis of the topography, aerial satellite imagery, and geologic mapping were performed to identify areas for on-site investigation. The validity of these data was confirmed by a ground-truthing field exercise in December 2012. Work in this designated area continued during March and June 2013. Lithic surface-scatters/sites were discovered on the hills capped with (knappable) chert that surround and overlook large depressions, which appear to be fluvial in origin and may indeed have been palaeochannels and palaeolakes (geomorphological modelling suggests that this area of Qatar has remained above sea level for at least the past two million years). The initial analysis of the assemblages from the twenty-one lithic surface-scatters/sites discovered to date (June 2013) indicates that one lithic assemblage can be equated to Qatar Neolithic Group B. Of particular importance however, are the other twenty lithic assemblages that certainly predate the Neolithic (technologically and in terms of patination), appear to include two distinct assemblage types, and may represent two relatively contemporary specialized stages of the chaîne opératoire, or indeed two completely different phases of the Palaeolithic. It is envisaged that the next stage of this research will include the collection of sufficient lithics from each scatters to facilitate rigorous techno-typological analysis; further investigation of particular lithosoils that may well incorporate embedded/stratified lithics; geomorphological investigations in the depressions; and the discovery of more lithic surface-scatters/sites with the aim of resolving the long-standing debate on the stone-age history of Qatar.
Stratigraphy and Petroleum Systems of the Palaeozoic (Pre-Khuff) Succession, Qatar
Journal of Petroleum Geology, 2016
A thickness of more than 1500m of Palaeozoic (pre-Khuff) siliciclastic strata were encountered in three deep wells (Matbakh A, and Dukhan A and B) drilled in the State of Qatar. These sedimentary rocks have no formal entries in the Qatari Geologic Lexicon and were not included in sequence stratigraphic schemes of the Arabian Plate region. The rocks are investigated here using cores, well logs and other materials. The pre-Khuff succession has been divided from the base up into the Qasim, Qusaiba, Sharawra, Tawil and Unayzah Formations based on age, stratigraphic status, lithology, sedimentary structures and correlation with the Saudi stratigraphic nomenclature. The succession is divided into a series of thirdorder sequences based on the identification of the principal maximum flooding surfaces. Deposition is interpreted to have occurred in a wide range of environments ranging from fluvial to shallow-marine but with the absence of the glacial facies which are prevalent in the equivalent Saudi section. Core and log analyses indicate that the Qusaiba Formation represents an important source rock which became mature for hydrocarbon generation during the Late Permian; it generated oil until the Late Jurassic and then began to expel gas and condensates, continuing until the present day. Both the Qasim and Sharawra Formations may include potential reservoir rocks which merit further study. The new nomenclature reported here will assist with the understanding of the Palaeozoic palaeogeography across the Arabian Peninsula and will help to delineate reservoir rocks in the Qatari Palaeozoic succession.
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen
The stratigraphic and palaeogeomorphologic conditions of the Qahlah Formation deposition in the United Arab Emirates are related to the geotectonic evolution of the western Oman Mountains during the Late Cretaceous. The Qahlah Formation ranges from a few metres to more than 70 m in thickness. It is the first sedimentary deposit to onlap the abducted Semail ophiolite, which was subjected to extensive weathering in a tropical environment during the Maastrichtian. Erosion accompanied the transgression of the Maastrichtian sea across the region. The sedimentary sequence can be divided into four facies: ophiolitic breccia, ophiolitic conglomerate, lateritic ferruginous siltstone and lithic sandstone. These sediments were probably formed in a shallow-marine to beach setting adjacent to a retreating cliff line of the ophiolite. A comparative analysis of the principal chemical and mineralogical components of the different facies indicates a genetic relationship between them. The nickel content (0.85-l-1.16 wt%) in the laterite facies is of economic interest as a low-grade ore provided that larger reserves can be identified.
A geomorphological and hydrological underpinning for archaeological research in northern Qatar
This paper examines occupation and settlement in northern Qatar in terms of a physical (geomorphological and hydrogeological) and temporal (climatic and eustatic) framework. Under the present arid/hyper-arid climate and low relief there is no perennial surface water. Potable water was obtained from groundwater, which occurs as a fresh-water lens overlying saline water; it was accessed by hand-dug wells which were concentrated closer to the coast where the freshwater table is shallowest. There is a close relationship between water table level depth under the Qatar peninsula and sea level, which was mostly lower than at present in Late Quaternary times, being at minus 120-130 m about 18,000 years ago and minus 40 m 10,000 years ago. During the Epipaleolithic, Upper Palaeolithic, and much of the Middle Palaeolithic periods back to the end of the last wet interglacial (Eemian) from 117,000-130,000 years ago, sea levels were low and groundwater was deep and unattainable, making permanent occupation unlikely. The onset of the Indian Ocean Monsoon in the Early Holocene overlapped with high interglacial sea levels in the mid-Holocene, providing a Hydrological Optimum from c.7000 to c.6000 years BP, when sea level reached c.3 m above that at present. Water was readily available with the likelihood of significant coastal spring outflow, at a time before the development of the saline coastal sabkha, where outflowing groundwater is now lost. It corresponds to the period of some of the most important pre-Islamic archaeological sites in Qatar, situated on the high-level shoreline at al-Shagra, al-Khor, and across the Abaruk (al Buriiq) peninsula/Dasah (Da'sah)/Dukkan (Dukhan) area. The retreat of the monsoon at c.6000 years BP ushered in a period of shallow hand-dug wells with settlements concentrated nearer the coast, especially in the north where the freshest groundwater occurs. This phase lasted until c. 1960 when the introduction of large wells and bores with modem pumps greatly reduced the size of the freshwater lens causing up-coning of salt water into the wells and salinization of the coastal aquifers by seawater intrusion.
Geoarabia -Manama-
The Miocene deposits of the Dam Formation were deposited in a narrow seaway stretching along the western edge of the Qatar Arch. During the initial stages of basin evolution the rising Zagros Mts. delivered debris in this fore deep basin. The paleocurrent and paleogeographic zonation are reflected by the heavy mineral assemblage, by the spatial distribution of phyllosilicates and the various types of sulphate. From NW towards the SE, the contents of smectite and palygorskite increase, whereas the illite and kaolinite contents decrease. Mega crystals of gypsum are found in the NW and massive fine-grained gypsum in the SE of the basin. During the waning stages of basin subsidence, the Arabian Shield became more and more important as a source for the Miocene sediments. In this study, the Dam Formation was subdivided into 7 members/lithofacies associations (lower, middle, upper Salwa, and Al Nakhsh Members, Abu Samrah Member). The Salwa Members at the base of the Dam Formation consists of heterolithic siliciclasticcalcareous sediments which were laid down under meso-to microtidal conditions. The Al Nakhsh Members formed under macrotidal conditions with sub-to supratidal depositional environments passing into continental ones. Celestite, gypsum, and microbial mats (stromatolites) are very widespread in these sabkha sediments. Crystals of gypsum and the thickness of stromatolites tremendously increase towards younger sediments indicating thereby a close genetic link between growth of microbial domes and gypsum precipitation. Throughout the Abu Samrah Member marine calcareous sediments were deposited in a microtidal wave-dominated environment. Dissolution of Eocene evaporites at depth governed the lithofacies differentiation in the Miocene Dam Formation.
Sediment-filled karst depressions and riyad – key archaeological environments of south Qatar
E&G Quaternary Science Journal, 2020
Systematic archaeological exploration of southern Qatar started in the 1950s. However, detailed local and regional data on climatic fluctuations and landscape changes during the Holocene, pivotal for understanding and reconstructing human-environment interactions, are still lacking. This contribution provides an overview on the variability of geomorphic environments of southern Qatar with a focus on depression landforms, which reveal a rich archaeological heritage ranging from Palaeolithic(?) and Early Neolithic times to the Modern era. Based on a detailed geomorphic mapping campaign, sediment cores and optically stimulated luminescence data, the dynamics of riyad (singular rawdha; shallow, small-scale, sediment-filled karst depressions clustering in the central southern peninsula) and the larger-scale Asaila depression near the western coast are studied in order to put archaeological discoveries into a wider environmental context. Geomorphic mapping of the Asaila basin shows a much greater geomorphic variability than documented in literature so far with relict signs of surface runoff. An 8 m long sediment core taken in the sabkha-type sand flats of the western basin reveals a continuous dominance of aeolian morphodynamics during the early to mid-Holocene. Mounds preserved by evaporite horizons representing capillarites originally grown in the vadose zone are a clear sign of groundwater-level drop after the sea-level highstand ca. 6000-4500 years ago. Deflation followed the lowering of the Stokes surface, leaving mounds where the relict capillarites were able to fixate and preserve the palaeo-surface. Abundant archaeological evidence of Early and Middle Neolithic occupation-the latter with a clear focus inside the central Asaila basin-indicate more favourable Published by Copernicus Publications on behalf of the Deutsche Quartärvereinigung (DEUQUA) e.V. 216 M. Engel et al.: Archaeological environments of south Qatar living conditions than today. In contrast, the sediment record of the investigated riyad in the south is very shallow, younger and controlled by surface discharge, deflation and the constantly diminishing barchan dune cover in Qatar over the Middle and Late Holocene. The young age of the infill (ca. 1500 to 2000 years) explains the absence of findings older than the Late Islamic period. Indicators of current net deflation may relate to a decrease in surface runoff and sediment supply only in recent decades to centuries. In the future, geophysical prospection of the riyad may help to locate thicker sedimentary archives and the analysis of grain size distribution, micromorphology, phytoliths or even pollen spectra may enhance our understanding of the interplay of regional environmental changes and cultural history. Kurzfassung: Die systematische archäologische Erkundung des Südens der katarischen Halbinsel begann in den 1950er Jahren. Lokale und regionale Daten zu den die regionale Kulturentwicklung begleitenden klimatischen Schwankungen und Landschaftsveränderungen im Holozän fehlen allerdings weitgehend. Dieser Beitrag liefert einen Überblick über die geomorphologische Variabilität des südlichen Teils von Katar mit einem Schwerpunkt auf karstbürtigen Hohlformen, deren verhältnismäßig reiches archäologisches Erbe bis in das Paläolithikum(?)/Frühe Neolithikum zurückreicht. Basierend auf einer detaillierten geomorphologischen Kartierkampagne, Sedimentkernen und Altersdatierung mit Hilfe optisch stimulierter Lumineszenz erfolgt eine Rekonstruktion der Sedimentationsgeschichte der räumlich bedeutenden Riyad (Singular: Rawdha; flache, kleinskalige, sedimentgefüllte Karsthohlformen) und des größeren Beckens von Asaila in der Nähe der Westküste, um die während der vergangenen Dekaden getätigten archäologischen Funde und Erkenntnisse in einen erweiterten Umweltkontext einzuordnen. Die geomorphologische Kartierung des Asaila-Beckens zeigt eine weit größere Variabilität an Oberflächenformen als bisher in der Literatur dokumentiert, darunter auch deutliche Indikatoren für reliktischen Oberflächenabfluss. Während der 8 m lange Sedimentkern aus dem sabkhaähnlichen Bereich des westlichen Beckens eine kontinuierliche Dominanz der äolischen Morphodynamik über das frühe bis mittlere Holozän andeutet, sind die von kleinen hügelartigen Formen dominierten Bereiche durch reliktische, einst in der vadosen Zone gewachsene kapillare Evaporithorizonte fixiert worden. Dies ist ein deutliches Zeichen für vorherrschende Deflation seit dem Hochstand des Meeresspiegels (und des Grundwasserspiegels) vor ca. 6000-4500 Jahren. Zahlreiche früh-und mittelneolithische Streufunde-letztere mit einem klaren Schwerpunkt im zentralen Asaila-Becken-weisen auf günstigere Lebensbedingungen zu dieser Phase hin. Die sedimentäre Füllung der untersuchten Riyad ist deutlich flacher und jünger und wird durch Oberflächenabfluss, Deflation und die sukzessiv abnehmende Barchan-Dünenbedeckung in Katar während des Mittel-und Spätholozäns determiniert. Das junge Alter der Füllung (ca. 1500-2000 Jahre) erklärt das Fehlen archäologischer Funde, die älter als spätislamisch datieren. Indikatoren aktuell dominierender Deflation (lineare Korrasionsrillen, Mikro-Yardangs) sind mögliche Hinweise auf einen Rückgang von Oberflächenabfluss und Sedimenteintrag innerhalb der letzten Jahrzehnte bis wenigen Jahrhunderte. Eine geophysikalische Prospektion der Riyad, die die Lokalisierung möglichst mächtiger Sedimentpakete erlauben würde, in Kombination mit der Analyse von Korngrößenverteilung, Mikromorphologie, Phytolithen oder gar Pollenspektren, könnte in Zukunft Teil einer Strategie sein, hier detailliertere Daten zur Paläo-Umweltdynamik der zentralen Bereiche Katars zu generieren.
Journal of Petroleum Geology, 2001
During the subsequent Kimmeridgian lowstand, gypsum wedges were laid down in the intrashelfbasins. Slight changes in water depth, which exposed orjooded these barriers, are believed to be responsible ,for the cyclic nature of the Arab Formation sediments. Arab Formation cycles show a 4"' orderfrequency but have thicknesses more typical of Yd order Vail-type sequences. This is probably explained by the 41h order flooding events merely topping-up pre-existing accommodation space of tens of metres water depth in the intrashelf basin. Diagenesis associated with movement of hypersaline brines may have been responsible for the development ofwidespread dissolution porosity and dolomitization. The laminated, organic-rich, bituminous lime mudstones of the Hanifa/Jubaila Formations are the probable source of oil in the Arab Formation in Qatar: The main reservoir types are oolitic-peloidal grainstones and dolomitized limestones.