Rosenberg T.M.,University of Bern |
Preusser F.,University of Stockholm |
Risberg J.,University of Stockholm |
Plikk A.,University of Stockholm |
And 4 more authors.
Quaternary Science Reviews | Year: 2013
Present climate in the Nafud desert of northern Saudi Arabia is hyper-arid and moisture brought by north-westerly winds scarcely reaches the region. The existence of abundant palaeolake sediments provides evidence for a considerably wetter climate in the past. However, the existing chronological framework of these deposits is solely based on radiocarbon dating of questionable reliability, due to potential post-depositional contamination with younger 14C. By using luminescence dating, we show that the lake deposits were not formed between 40 and 20ka as suggested previously, but approximately ca 410ka, 320ka, 200ka, 125ka, and 100ka ago. All of these humid phases are in good agreement with those recorded in lake sediments and speleothems from southern Arabia. Surprisingly, no Holocene lake deposits were identified. Geological characteristics of the deposits and diatom analysis suggest that a single, perennial lake covered the entire south-western Nafud ca 320ka ago. In contrast, lakes of the 200ka, 125ka, and 100ka humid intervals were smaller and restricted to interdune depressions of a pre-existing dune relief. The concurrent occurrence of humid phases in the Nafud, southern Arabia and the eastern Mediterranean suggests that moisture in northern Arabia originated either from the Mediterranean due to more frequent frontal depression systems or from stronger Indian monsoon circulation, respectively. However, based on previously published climate model simulations and palaecolimate evidence from central Arabia and the Negev desert, we argue that humid climate conditions in the Nafud were probably caused by a stronger African monsoon and a distinct change in zonal atmospheric circulation. © 2013 Elsevier Ltd.
Khater G.A.,Saudi Geological Survey
Journal of Non-Crystalline Solids | Year: 2010
Cement kiln dust from Rabigh plant in Saudi Arabia was examined for use in the preparation of glass-ceramic materials. The cement kiln dust made up about 70 wt.% of the batch constituents depending on the composition. The cement kiln dust composition was sometimes modified by additions of other ingredients such as silica sand, granite and magnesite. The batches were melted and then casted into glass which was subjected to heat treatment to induce crystallization. Different techniques were used in the present study, including differential thermal analysis, polarizing microscope, X-ray diffraction and indentation microhardness. The colored glass and glass-ceramic materials obtained, possess very high hardness indicating high abrasion resistance, which make them suitable for many applications under aggressive mechanical conditions. © 2010 Elsevier B.V. All rights reserved.
Matter A.,University of Bern |
Neubert E.,Natural History Museum Bern |
Preusser F.,University of Stockholm |
Rosenberg T.,University of Bern |
Al-Wagdani K.,Saudi Geological Survey
Quaternary International | Year: 2015
Shallow lakes and sabkha deposits are evidence of past periods of higher groundwater table than today, and hence reflect increased humidity in the Rub' al-Khali, the large desert in the southern part of the Arabian Peninsula. Reported here are the observations made during four expeditions into this remote area in combination with luminescence dating constraining the age of the deposits. The results presented extend the spatial coverage of evidence and show that most of the deposits correlate to MIS 5 (ca. 130-70. ka) and the Early/Mid Holocene (ca. 11-5.5. ka). A single sample points towards potentially more humid conditions during the transition MIS 4/3 (ca. 65-55. ka). The presence of the mussel Unio in some of the deposits attributed to MIS 5 is indirect evidence for the presence of fish in the lakes, which must have supported a rich and diverse fauna (and probably also flora). Together with other evidence, this demonstrates that a number of small persistent lakes were spread across the Rub' al-Khali for at least some of the time. These lakes would not only have been a potential source of freshwater but could also have provided an additional and easy accessible food source via the fish for humans migrating through the area. The presented palaeoenvironmental data underlines that parts of MIS 5 represent a time window of opportunity for a potential expansion of modern humans across Arabia. © 2014 Elsevier Ltd and INQUA.
Cox G.M.,University of Adelaide |
Lewis C.J.,University of Adelaide |
Collins A.S.,University of Adelaide |
Halverson G.P.,University of Adelaide |
And 5 more authors.
Gondwana Research | Year: 2012
The Ad Dawadimi Terrane is an Ediacaran basin of the Arabian Nubian Shield (ANS), Saudi Arabia. This basin terrane is situated in the far eastern part of the ANS and represents the youngest accretion event of the exposed ANS. Therefore, the timing of events within the basin is key to understanding both the closure of the Mozambique Ocean and the amalgamation of Gondwana along the northern East African Orogen. Here we present U/Pb detrital zircon data for the Abt Formation, the principle basin sediments of the Ad Dawadimi Terrane, along with 40Ar/ 39Ar ages on muscovite and whole rock Sm/Nd data. These data indicate that deep-water deposition in the Abt Basin did not end until after ca. 620Ma and that deformation and greenschist-facies metamorphism of the Abt Formation occurred at 620±3 (2σ) Ma along an active margin. This is the youngest terrane amalgamation event reported so far in the Arabian-Nubian Shield, but we suggest even younger sutures lie further east beneath the Phanerozoic cover of eastern Saudi Arabia. Our results suggest that the Ediacaran basins of the eastern ANS were not part of the Huqf basin in Oman, which was instead part of a passive margin of Neoproterozoic India, separated from the active margin of Africa by the Mozambique Ocean that probably did not close until the late Ediacaran or early Cambrian. © 2011 International Association for Gondwana Research.
Nasiri Bezenjani R.,University of Stockholm |
Pease V.,University of Stockholm |
Whitehouse M.J.,Swedish Museum of Natural History |
Shalaby M.H.,Nuclear Materials Authority |
And 2 more authors.
Precambrian Research | Year: 2014
Detrital zircon U-Pb SIMS dating is used to evaluate the provenance of two correlative basins in the Arabian-Nubian Shield (ANS). The Wadi Igla Formation in the Central Eastern Desert (CED) of Egypt and the Thalbah Group in the Midyan Terrane (MT) of NW Saudi Arabia are considered to be post-amalgamation terrestrial basins, developed during closure of the Mozambique Ocean and amalgamation of the ANS in Cryogenian-early Ediacaran time. The analytical results indicate that the upper-part of the Wadi Igla Formation has a maximum depositional age of 628 ± 6. Ma, contains 98% Neoproterozoic zircon with ages between 815 and 628. Ma, and has two distinct peaks at 690. Ma and 652. Ma. A rhyolite clast from the upper-part of the Wadi Igla Formation gives a U-Pb age of 700 ± 6. Ma. This age significantly pre-dates Dokhan volcanism, indicating that the dominant rhyolitic clasts within the Wadi Igla Formation are not from the Dokhan Volcanics, as previously believed. Analytical results from the Thalbah Group suggest multiphase basin formation and development. The lower part of the Thalbah Group is intruded by monzogranites of the Liban complex, has a minimum depositional age of 635 ± 5. Ma, resembling that of the Wadi Igla Formation. Its middle part has a maximum age of 612 ± 7. Ma and is comprised of 90% Neoproterozoic zircon with ages ranging from 820 to 612. Ma. The upper part of the Thalbah Group has a maximum age of 596 ± 10. Ma and contains a wider range of Neoproterozoic detritus with ages between 985 and 596. Ma. The basement of the Thalbah Group is represented by metasediments and metavolcanics of the Zaam Group. The sample collected from the uppermost part of the Zaam Group (Um Ashsh Formation) contains zircon of mostly Cryogenian age (ca. 812-697. Ma) and has a maximum age of 700 ± 4. Ma, suggesting that the Zaam Group might be correlative with the subduction-related metavolcanic and metasedimentary rocks that are overlain unconformably by the Wadi Igla Formation in the CED. The Wadi Igla basin and the lower and middle parts of the Thalbah basin have similar provenance, record a Cryogenian-early Ediacaran age, and represent syn-subduction (rather than post-amalgamation) basins. The upper part of the Thalbah Group, in contrast, has a distinct provenance representing an Ediacaran syn-collisional basin. The narrow age range of the Wadi Igla Formation and the lower and middle parts of the Thalbah Group indicates a restricted source from the CED and MT island arc basement, whereas the wide age range for the upper part of the Thalbah Group indicates a contribution from other parts of the ANS. The sediment sources and the age patterns of detrital zircons change abruptly at ca. 596. Ma. This may coincide with the onset of collision of the CED and MT basements with the older Hijaz-Gebeit terrane (850-680. Ma) to the south along the Yanbu-Onib-Sol Hamed-Gerf-Allaqi-Heiani (YOSHGAH) suture in the ANS during the East African Orogeny. © 2013 Elsevier B.V.