Geotrekking in Southeastern Arabia: a Guide to Locations of World-Class Geology

220 Pages·2012·161.99 MB·English

by  Benjamin R. Jordan(auth.)

Geotrekking
in
Southeastern Arabia
A Guide to Locations of World-Class Geology
Benjamin R. Jordan
Published under the aegis of the AGU Books Board
Kenneth R. Minschwaner, Chair; Gray E. Bebout, Kenneth H. Brink, Jiasong Fang,
Ralf R. Haese, Yonggang Liu, W. Berry Lyons, Laurent Montési, Nancy N. Rabalais,
Todd C. Rasmussen, A. Surjalal Sharma, David E. Siskind, Rigobert Tibi,
and Peter E. van Keken, members.
Library of Congress Cataloging-in-Publication Data
Jordan, Benjamin R., 1972-
Geotrekking in Southeast Arabia : a guide to locations of world-class geology /
Benjamin R. Jordan.
pages cm
Includes bibliographical references and index.
ISBN 978-0-87590-735-2
1. Geology—United Arab Emirates. 2. Geology—Oman. I. Title.
QE291.U5J67 2012
555.35—dc23
2012027599
ISBN: 978-0-87590-735-2
Book doi: 10.1029/SP065
Copyright 2012 by the American Geophysical Union
2000 Florida Avenue, NW
Washington, DC 20009
Front cover: Examples of the geological variety of southeastern Arabia. (top) Erosional
pillars rising above the Abu Dhabi, UAE, sabkha and (bottom) the coastal cliffs and
drowned river valleys of Oman’s Musandam Peninsula.
Figures, tables, and short excerpts may be reprinted in scientific books and journals if
the source is properly cited.
Authorization to photocopy items for internal or personal use, or the internal or
personal use of specific clients, is granted by the American Geophysical Union for
libraries and other users registered with the Copyright Clearance Center (CCC). This
consent does not extend to other kinds of copying, such as copying for creating new
collective works or for resale. The reproduction of multiple copies and the use of full
articles or the use of extracts, including figures and tables, for commercial purposes
requires permission from the American Geophysical Union. geopress is an imprint of
the American Geophysical Union.
Printed in the United States of America.
CONTENTS
Preface ........................................................................................................v
Introduction .................................................................................................1
Route 1: Abu Dhabi Sabkha, United Arab Emirates .................................16
Route 2: Liwa, United Arab Emirates .......................................................38
Route 3: Al Ain and Jebel Hafeet, United Arab Emirates ..........................60
Route 4: Jebel Huwayya (Fossil Valley), Oman .......................................90
Route 5: Wadi Madbah, Oman .............................................................102
Route 6: Wadi Al Jizzi, Oman ...............................................................120
Route 7: Rustaq Area, Oman .................................................................148
Route 8: Hatta to Khalba, United Arab Emirates ....................................168
Route 9: Musandam, Oman ..................................................................190
Appendix A: Overview ............................................................................205
Bibliography ............................................................................................245
Index .......................................................................................................249

Preface
Whenwritingabooksuchasthisonanareaasgeologicallyfantasticanddiverseas
theUnitedArabEmirates(UAE)andtheSultanateofOman(Oman),therearebound
tobemanyquestionsalongthelinesof“Butwhatabout...?”or“Whydidn’tyou
include...?”Thespectaculargeologyoftheregioncannotbecontainedinonebook.
Ididnotevenremotelydecidetotrysuchanundertaking.Thisbookwaswrittento
providespecificandclearlocationinformationonaselectfewsitesthatrepresentthe
mosteasilyaccessible,yetpremierexamplesofthegeologyoftheregion.
Ihighlyencourageexplorationoutsidetheconfinesofthisbook.Thereismuchto
seeanddiscoveronyourown,whetheryouareatouristwantingtoknowalittleof
thegeologichistoryofthearea,aresearcherwantingtostudytheareaindetail,ora
residentcuriousaboutthegeologicheritageoftheareainwhichyoulive.Thebook
canbeastart,butitcertainlyisnottheend.
Theemphasisinthisbookisongettingtothelocationsthatmanywouldliketosee,
butdonotknowhowtoreach,especiallyiftheyarefromoutsidetheUAEorOman.
Thereisnocomparableguideavailable.Thereareseveralotherguidestothegeology
of the area, but the most recent and up-to-date examples do not have location
information,onlygeneral(butverygood)descriptionsofthegeologyofthearea.The
actualdescriptionsinthisbookarefairlybrief,andforthoseinterestedIrecommend
thatyouseekoutthoseadditionalresources(whicharelistedinthisbook).
Itishopedthatthisbookwillserveasaguideandahelpfulintroductiontoafewof
thelocationsintheUAEandOmanthatareexamplesofsomeoftheworld’sfinest
geology. It is written for anyone interested in understanding the Earth and its
processes. Each route includes directions, photographs, and explanations of why a
particularlocationisspecial.Also,becauseitishopedthattheuserwillseemorethan
thebookcanpossiblycover,ahandyidentificationguidetothemostcommonrocks,
minerals, and fossils likelytobe seenisincluded in the back, alongwithpages for
notes.Thisbookismeanttobebothusefulandused.Itismyhopethatitwillbe.
Manypeoplehavecontributedtothecompletionofthisbook.Iwouldfirstliketo
expressmygratitudetomycolleaguesatUnitedArabEmiratesUniversity(UAEU)
v
Geotrekking in Southeastern Arabia
who introduced me to the region: Fadhil Sadooni (now at Environmental Studies
Center, University of Qatar), Ahmed Murad, Haydar Baker, Esam Abdelgawad,
Abdallah Musallam, Osman Abdelghany, Abdurrahman Tom Fowler, Sulaiman
Alabed, Salem Essa, Fares Howari (now at Abu Dhabi University), Bahaa
Mahmoud, Wahid Abdel Hafez, Ayman El-saiy, Amir Gabr, Mahmoud Abu-
Saima, Mostafa Lotfy (no longer at UAEU), Gaber Lattif, Hamdi Kandil, Wajeeh
Kittana, and Omer Al-Basher.
IwouldalsoliketothankWarrenWood,TomVogel,DavidHyndman,andPaulo
Hidalgo of Michigan State University, along with Gary Byerly of Louisiana State
UniversityandTomTaylorofShellOilCompanyfortheirinformativediscussions
ofthegeologyoftheUnitedArabEmiratesandOmanandtheirencouragementto
preparethisguide.
A special thanks goes to Dennis Dahl, my frequent traveling companion and
fellowexplorer,whospentmanydayswithme,discoveringmostofthelocationsin
thisbook.AnothergoodfriendandfellowexplorerisJarodGardner,whowillingly
traveled with me to the Middle East to help me confirm my routes. We are both
grateful to Jonathon and Wendy Penny, who opened their home to us during our
travels.Iwouldalsoliketothankmysister,JulieJones,whosecuriosityledtothe
discoveryofthesaltpondonRoute1andthedesertrosesofRoute2.
Manyothershavegenerouslyallowedmetousetheirmapsandillustrations,and
IamverygratefulthatIdidnothaveto“reinventthewheel.”EricChristiansen,of
Brigham Young University, let me use many figures from his and Kenneth Ham-
blin’s highly regarded geology text; Ron Blakey, of Northern Arizona University,
allowed me the use of his fantastic illustrations of Earth’s ancient geography;
ChristopherKendall,oftheUniversityofSouthCarolina,graciouslyletmerepro-
ducehisgeologicmapoftheAbuDhabisabkha;andRichardLillyreadilyallowed
metheuseofhisgeologicmapoftheHatta(UAE)area.
IcannotsayenoughaboutLindaMitchell,whopreparedor“touchedup”almost
every figure in the book, and Robert Holman, who prepared all of the route maps.
SomeofmyfieldworkwasgenerouslyfundedbytheBYU-IdahoThomasE.Ricks
facultyresearchfundoffice,alongwiththeBYU-IdahoCollegeofPhysicalSciences
andEngineeringandtheBYU-IdahoDepartmentofGeology.Mythankstheregoto
DanMoore,KendallPeck,DonetteRingel,GracieHill,andPhillipAllred.
I express gratitude to AGU Books staff for encouragement and for seeing the
bookthroughfromthebeginningtotheend.
Iespeciallythankmywife,Michelle,whosupportedmethroughoutthisendeavor.
Mychildren,Katherine, Colin,andStephanie,whooftenexploredthelocationsin
this book with me, were a pleasure to travel with. To all my other friends and
associates in the Middle East I express my love and appreciation. They made my
family’stimetheretrulywonderful.
BenjaminR.Jordan
Oahu,Hawaii
vi
Introduction
TherearemanyguidebookstothecountriesoftheSultanateofOman(Oman)and
the United Arab Emirates (UAE). There is a good reason for this: there are
numerous tourists that visit these countries and there is a lot to see and do. Most
ofthetouristscomeforthecultureandtheshopping.However,asmallbutregular
groupoftouristscomestotheregionforacompletelydifferentreason–tolookat
rocks. That is because the rocks of southeast Arabia are special and unique.
Geologistscomefromallpartsoftheworldseethemfirsthand,tostudythem,and
gainagreaterunderstandingoftheprocessesthathaveshapedthewholeEarth.The
HajarMountainsoftheUAEandOmanaretheworld’slargestandbestpreserved
ophiolite – a slice of the deep ocean crust that has been forced by tectonic forces
onto a continent. Within these mountains are sections of the deep Earth, rarely
exposedanywhere–piecesoftheEarth’smantleandthelowerpartsofitsoceanic
crust; deep sea sediments and volcanic rocks that were erupted by submarine
volcanoes; and copper deposits formed at ancient, deep sea, hydrothermal vents.
Inaddition,groundwaterflowingoutofophioliterocksreactswiththeatmosphere
to precipitate calcite and form pools that appear as blue as any man-made swim-
mingpool.
Iftheophiolitewasallthatwashereitwouldbeenoughtosatisfyanygeologist.
However,theshallowlandandhighevaporationconditionsinthewesternregionof
the UAE forms giant, salt-lined mudcracks and the growth of gypsum clusters
called“desertroses.”Inthisregiontherearestromatolites–coloniesofcyanobac-
teriathatareprobablysomeoftheoldestlivingspeciesonEarth.Thentherearethe
dunes of Liwa, UAE, some of which rise 160 m above evaporative salt plains.
Theseandmanyothergeologicmarvelsexistinaregionknownmoreforitsoiland
gas geology. Oil and gas are found in many places, but few places on Earth have
100 million-year-old pillow lavas, which form underwater, preserved as if they
wereeruptedyesterday,ormudcracksthatarethesizeofacar.
1
Geotrekking in Southeastern Arabia
Geologic Structure
InordertounderstandthegeologyofsoutheastArabiaitisimportanttounderstand
thestructureoftheEarth.TheEarthismuchlikeanegg,withahard,brittle,outer
shellandasoft,butsolid,interior.Theshell,inasense,“floats”onthehot,“plastic”
rocksbelow.However,unlikeanegg,theinterioroftheEarthcanbedescribedby
geologistsbyeitheritschemicalorphysicalcharacteristics.Whenitisdescribedby
its chemical characteristics it only has three layers: a core, mantle, and crust. The
Coreismadeofiron(Fe)andnickel(Ni),withalittlebitofsulfur(S).TheMantle
consistsofmostlyiron(Fe),magnesium(Mg),andsilica(Si).TheCrustismostly
silica(Si)withlotsofaluminum(Al)andcalcium(Ca).WhentheEarthisdescribed
byitsphysicalcharacteristicsithasaninnercore,outercore,mesosphere,astheno-
sphere, and lithosphere. The lithosphere thus includes both the upper part of the
mantleandthecrustandishardandbrittle.Theboundarybetweenthecrustandthe
mantleiscalledthe“Moho,”whichisshortfor“Mohorovičićdiscontinuity”andis
namedafterAndrijaMohorovičić,aCroatianseismologistwhofirstdescribeditin
1909. The lithosphere “floats” on the asthenosphere, which is solid, but soft, like
modelingclay.SeeFigureI.1.
The lithosphere is broken into vast regions of the Earth’s surface called plates
(Figure I.2). These plates of the lithosphere move in relation to one another in a
processcalledPlateTectonics.Insomeareastheymoveapartinlargerifts,which
splittheEarthandallowmagmageneratedintherisingasthenospheretoreachthe
Earth’ssurface,formingvolcanoesandnewrocks.Inotherareastheplatescollide
Figure I.1. Cross-section of the earth illustrating the layers within the Earth, which are
definedeitherbytheirchemicalortheirphysicalcompositions.Theyellowsquareindicates
theapproximateregionofsoutheastArabiacoveredbythisguide.
2
Introduction
FigureI.2.AgeneralizedmapofEarth’smajortectonicplates.TheArabianplateislocated
ontherightandismovingnortheast–collidingwithpresent-dayIranandformingtheZagros
MountainsalongthewesternedgeofIran.TheriftcreatedasArabiamovesawayfromAfrica
iswhatformstheRedSea.IllustrationbyLindaMitchell[afterHamblinandChristiansen,
2004].
FigureI.3.Mostoftheworld’svolcanismtakesplacewhereplatesareeithermovingapartor
colliding.Usuallytherocksformedatamid-oceanridgesinkbackintotheEarth.Sometimes,
however, slices of oceanic crust will be thrust onto continental crust during collision and
subduction. The Hajar Mountains of the United Arab Emirates and Oman are the best
preservedexampleofoneoftheseslices.IllustrationbyLindaMitchell(figurenottoscale).
3
Geotrekking in Southeastern Arabia
FigureI.4.Across-sectionthroughamid-oceanridgeillustratingtheprocessesthatproduce
the stratigraphyillustrated inFigure I.6.Illustration by Linda Mitchell[after Murck etal.,
2008].
andpushupmountains,oronewillsinkasitispulledbygravitybeneathanother.
This sinking is called subduction and leads to volcanoes as water, which was
absorbed from the ocean by rocks underlying the seafloor, is released from the
sinkingplateandlowersthemeltingtemperatureoftheasthenosphereitissinking
through (much like salt lowers the melting temperature of ice). This causes the
asthenospheric rock to melt and form a magma that rises to the surface where it
eruptsthroughtheoverlyinglithosphereandcrust[TatsumiandEggins,1995].See
FigureI.3.Finally,plateswillalsoslidepasteachotherandformlonglinesoffaults
suchasthosethatgeneratethefamousearthquakesofCaliforniaorTurkey,aswell
asthelesserknownfaultsintheMasafiandFujairahregionoftheUAE.Overtime,
new crust is formed at mid-ocean ridges as plates move apart, allow melting and
risingofmagmafromthemantle,andthencoolingandsolidifyingofthatmagmato
makenewcrust(FiguresI.4andI.5).Theresultisthatoceaniccrust/lithospherehas
Figure I.5. A cross-section of the formation of oceanic crust/lithosphere through time.
IllustrationbyLindaMitchell[afterHamblinandChristiansen,2004].
4