Geology of the Arabian Peninsula, Shield area of Western Saudi Arabia

198 Pages·1989·65.76 MB·English

by  GLEN F. BROWN

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1+ GEOLOGY OF THE
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ARAB~PENINSULA
Shield Area of
~\ Western Saudi Arabia
U.S. CfEOLOGICAL SURVEY PROFESSI AL PAPER 560-A
The Earth fromspace. Africa and Arabia lienorth ofthe Indian
and Atlantic Oceans, cloud-draped from the Antarctica Ice
Captothe Equator.
Acloser viewshowsnortheastAfrica,the Arabian Peninsula,and
the Arabian Sea. Photographs from Apollo17spacecraft at
about 100,000nauticalmilesfromEarth.
GEOLOGY OF THE ARABIAN PENINSULA
SHIELD AREA OF
WESTERN SAUDI ARABIA
FRONTISPIECE.-TheArabianShield.Asseenfromspace,theshieldappearsasaredcrescentonthewestsideoftheArabianPeninsulaandas
acontinuationofthe Sahara Desert extendingacrossnorthAfrica.PhotographfromApolloII spacecraftat about 98,000nauticalmiles
from Earth.
Geology of the Arabian Peninsula
Shield Area of
Western Saudi Arabia
ByGLEN F. BROWN, DWIGHT L. SCHMIDT,
and A. CURTIS HUFFMAN,JR.
U.S. GE0 LOG ICAL SU RVEY PRO FESSIO NAL PAPE R 56O-A
Prepared in cooperation with the
Ministry ofPetroleum and
MineralResources, DeputyMinistry
ofMineralResources,Jiddah,
Kingdom ofSaudi Arabia
A review ofthegeologyofwestern
Saudi Arabia as refinedfrom
u.s.
Geological Survey Miscellaneous
GeologicInvestigations Map I-270A,
"Geologic Map oftheArabian
Peninsula", 1963
UNIT ED STAT ES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1989
DEPARTMENT OF THE INTERIOR
(7 U8R'"'·.~R~~~f~··~("S")\
"IANUEL LUJA1'l,JR., Secretary
1. / ...... .-1
i
I ;" .
lS90
u.s. GEOLOGICAL SURVEY
Dallas L. Peck, Director
Any use oftrade, product,or firm names inthispublicationisfor
descriptivepurposesonlyanddoesnot imply endorsement bythe
U.S. Government
LibraryofCongressCatalogingin Publication Data
Brown, Glen Francis, 1911-
ShieldareaofWestern SaudiArabia.
(U.S.GeologicalSurveyprofessionalpaper;560-A)
"Areviewofthe geologyofwestern Saudi Arabiaasrefinedfrom U.S.GeologicalSurveymiscellaneous geologicinvestigations
map I-27O-A, 'GeologicmapoftheArabianPeninsula,' 1963."
Bibliography:p.
Supt.ofDocs.no.: I 19.16:560-A
1. Geology-Saudi Arabia. I. Schmidt, Dwight Lyman, 1926- . II. Huffman, A.C. III. Title. IV. Series: Geological
Surveyprofessionalpaper; 560-A.
QE29I.S28B76 1989 555.3'8 87-600038
For sale by the Books and Open-File Reports Section, U.S. Geological Survey,
Federal Center, Box 25425, Denver, CO80225
FOREWORD
This volume, "The Geology of the Arabian Peninsu geographic versions were to be printed for each of the
la," is a logical consequence of the geographic and quadrangles; both versions were to be bilingual-in
geologic mapping project of the Arabian Peninsula, a Arabic and English. A peninsular geologic map on a
cooperative venture between the Kingdom of Saudi scale of 1:2,000,000 was to conclude the project.
Arabia and the Government of the United States. The High-altitude photography, on a scale of 1:60,000, of
Arabian-American Oil Co. and the U.S. Geological the Kingdom ofSaudiArabiawas initiated during 1949
Survey did the fieldwork within the Kingdom of Saudi by the Aero Service Corp.and completed in 1959. Both
Arabia, and, with the approval of the governments of third-order vertical and horizontal control and shoran
neighboring countries, a numberof other oilcompanies were utilized in compiling the photography. This con
contributed additional mapping to complete the cover trolled photography resulted in highly accurate geo
age of thewholeoftheArabian Peninsula.Sofar as we graphicmaps atthe publicationscalewhichthen served
are aware, this is a unique experiment in geological as a base for the geologic overlay. The topography of
cooperation among several governments, petroleum the sedimentary areas was depicted by hachuring and
companies, and individuals. that of the shield region by shaded relief utilizing the
The plan for a cooperative mapping project was airbrush technique.
originally conceivedinJuly 1953by the late WilliamE. The first geographic quadrangle was published in
Wrather, then Director of the U.S. Geological Survey, July 1956 and the last in September 1962. While
the late James Terry Duce, then Vice President of preparationofthe geographicsheetswas inprogress, a
Aramco, and the late E.L. deGolyer. George Wads need arose for early publication of a 1:2,000,000-scale
worth, then U.S. Ambassador to Saudi Arabia, and peninsular geographic map. Consequently, a prelimi
SheikhAbdullah Sulaiman, then Minister of Finance of nary edition was compiled and published in both Eng
the Government of Saudi Arabia, lent their support to lish and Arabic in 1958.The second edition, containing
the plan. In November of the following year, 1954, additional photography and considerable new topo
Director Wrather approved the U.S. Geological Sur graphic and cultural data, was published in 1963. The
vey's participationand designated G.F.Brownresponsi first of the geologic map series was published in July
ble for the western Arabian shield region in which he 1956and the final sheet in early 1964.The cooperative
had previously worked under U.S. foreign-aid pro map project was completed in October 1963 with the
grams. InJanuary 1955,F.A. Davies, Chairman, Board publication of the 1:2,000,000-scale "Geologic Map of
of Directors, Arabian-American Oil Co., approved Ar the Arabian Peninsula" (Miscellaneous Geologic Inves
amco's participation and appointed the late R.A.Bram tigations Map 1-270 A).
kamp, chief geologist, responsible for compilation of As work on the quadrangles progressed, geologists,
the area withinthe Kingdom where the sediments crop companies, andgovernments working inareas adjacent
out. This responsibility fell to L.F. Ramirez following to the Kingdom of Saudi Arabia were consulted by
the death of R.A. Bramkamp in September 1958. Aramco and invited to participate in the mapping
R.A.Bramkamp and G.F. Brown met in New York in project. The number of cooperating participants was
February 1955 and planned the program, including expanded to 11,whichincludedtheoperating oilcompa
scales of maps, areas of responsibility,types of terrain niesinthepeninsulaand whichare identifiedelsewhere
representation, and bilingual names. Thus there was in this text; the Overseas Geological Surveys, London;
established acooperative agreementbetween the King the Government of Jordan; F. Geukens, who had
domofSaudiArabia, theU.S.DepartmentofState, and worked in Yemen; and Z.R.Beydoun, who had studied
the Arabian-American Oil Co. to make available the the Eastern Aden Protectorate. With the closecoopera
basicarealgeology as mapped by Aramco and the U.S. tion of the authors, the new data were added to data
Geological Survey. already plotted on the base map of the Arabian Penin
The agreement specified publication of a seriesof 21 sula.
maps onascaleof 1:500,000,eachmap covering anarea As the geological coverage of the peninsular map
30 oflongitudeand40 oflatitude.Separategeologicand grew, theneedfora textto accompany the mapbecame
v
VI FOREWORD
apparent to both the U.S. Geological Survey and the Cooperation and relations have been of the highest
Aramco geologists. Exploratory conversations were order in all phases of the work.The project would not
begun byAramco withcompanies working in the other have been possible without the fullsupport of the U.S.
countries of the Arabian Peninsula for their participa DepartmentofState, the KingdomofSaudiArabia,and
tion in the preparation of a monograph on the geology allcontributors.In fact,the funds whichmade publica
of the Arabian Peninsula. Each author prepared a tion of this volume possible were contributed by the
descriptionofthegeology of thearea for which he was Saudi Arabian Government.
responsible,as shown inthe sources of geologiccompi Thedata providedby the maps and inthe profession
lation diagramonthepeninsular map.The U.S.Geolog al paper provide information for an orderly scientific
icalSurvey undertook the publishingof the volumeasa and economic development of a subcontinent.
professional paper, and the Government of SaudiAra
bia was tofinanceits printing.It was earlyagreedthat O. A. SEAGER,
Arabian-American Oil Co. (Retired)
there wouldbe noeffort to confine thecontributions to
a standard format and that no attempt would be made w. D. JOHNSTON, JR.,
to work out an overall correlation chart other than Former Chief, Foreign Geology Branch,
shown on the "Geologic Map of the Arabian Peninsu U.S. Geological Survey (Deceased)
la." Thus, the individual style of authors of several
nationalities is preserved.
CONTENTS
Page Page
Foreword-------------------------------------------------------------------- V Crustal history of the Precambrian shield- Continued
Abstract------------------------------------------.-.--------------..--•....- Al Early collisional orogeny·-·····--··································A96
Introduction----------.------- --.----..•..- --.............. 2 Late crustal history····-·-················-····-···················· 98
Previous geologic work ....•....•....•...--------------.•---------- 4 Culminant orogeny and posttectonic granites -. 98
Nature and scope of recent work------------------------------- 4 Najd faulting event············-·········-···-···-···-·--···-··103
Acknowledgments-------------------------------------------.-------- 5 Age and strontium evolution - -- 105
Geography----------------------------------------------------------.--....- 7 Paleozoic sedimentary cover rocks at edge of the
Climate---....----------.--....---------.....--..•...•....•.........._-- 7 Arabian Shield····-···-·························-··············-105
Settlement.•...-...•...•.......•.•...•....•.........•.................- 10 Siq Sandstone..........•..•..........................- 105
Flora···················-········-·········-·········· - - 11 Saq Sandstone and Ram-Umm Sahm Sandstone - -- 107
Relation to geographic setting and human use··-···-·· 11 Wajid Sandstone - - - - 108
Relation of flora to rainfall, by J.D. Tothill -..-...---.- 12 Khuff Formation - --..-•....•...--...•...•.......-.109
The seven floral zones----------------------.---..----............. 14 Mesozoic sedimentary rocks -.......•................................109
Ar Rub' al Khal'izone-·-···----····················-···-····· 14 Khums Formation•..•..........•............................- -109
Samr desert zone -.....••...•....-....•....•....-- -... 15 Definition·········-··-···············-············-····-·····-····109
Sallam desert zone·····--·········-········-··············-···· 15 Occurrence and thickness.- --- --..- 109
Asak·Commiphora·desert zone.- -....- -....-...--..-- 15 Lithologic character··········-··-··············-···············110
Kleinia-pastoral zone .-.-..- - ---..- -.-..---.-.•....- 15 Paleontology and age..•............•....- 111
Eutyops·barley zone.•-.---- ------ -.............. 16 Amran Formation··············································-..-.. III
Rose-juniper-agricultural zone....•...•.....-................ 16 Definition - - ---..- --......•. III
Precambrian layered rocks of the Arabian Shield 17 Occurrence and thickness-..-..-.- -.-..-•.................113
Historic geologic divisions..-....-- - -...--- - - -... 17 Lithologic character···-··--··-···················-·············113
Current geologic divisions.--..-- - --..---..-- ---.--..- 18 Nature of contact--··--········································ 113
Ultramafic and ophiolitic rocks - -- ---........ 18 Paleontology and age.......•.........................-...-...113
Baish-Bahah Groups -.....-- --.........••...•.......... 19 Khurma Formation - - - --......•...114
Jiddah Group --.........•.....•........- -.......... 21 Mesozoic-Cenozoic sedimentary rocks ···········--···-···--··········115
Ablah Group - - - - -..- -. 22 Usfan Formation - - --..--....•................- 115
Fatimah Group···-···-··········-····-·········-····-·-··-···--· 24 Definition····-·············-··-···-······························-115
AI Ays Group-··-···--···-····-·····-····-····-····--··········· 25 Occurrence and thickness.....•.........- --.115
Silasia Formation --................................. 26 Lithologic character····-·················-···--···-······- 115
Halaban Group .- - - - - -.. 27 Nature of contact······-·······-·········--·-·····-············l16
Murdama Group -..- - -.- -- - - 29 Paleontology and age -.- --.~..•....•.................116
Shammar Group - -...- - -- --..-............... 31 Cenozoic rocks...•..-..-..-- - - -- 117
Jubaylah Group·······--··---···-·················-·········-··· 32 Umm Himar Formation (Paleocene) - -.- 117
Precambrian plutonic rocks of the Arabian Shield - -... 35 Definition·····································-···--··············117
Dioritic suite - - -- --..- 36 Occurrence and thickness.......•....•.........•.............118
Granitic suite.-- - --..-- - - -- -- --......... 37 Lithologic character·······································-···-118
Chemistry of the Precambrian crystalline rocks ..- -.... 37 Nature of contacts·························-···--··--·········· 119
Introduction - -.............•....•.....- - - -- - 37 Laterite and saprolite _ __..__ 119
Chemical variation of volcanic and plutonic rocks····-····-- 67 Shumaysi Formation -...•.......-....•-....•..................--120
Volcanic rocks ..- --.---..-- - -.- --•...•. 67 Definition····································-···-·····-·······-··120
Plutonic rocks..•....•...•....•...........•....•....•...........• 70 Occurrence and thickness - --..-..•.....120
Tholeiitic, calc-alkalic, and alkalic compositions···-··········· 74 Lithologic character······--···-··························-·····120
General statement - --- - -- -. 74 Nature of contacts······································-······120
Volcanic rocks -•...........•....•.....•.....•....... 74 Paleontology and age - - - 120
Plutonic rocks - - - -....... 79 Baid Formation -..-- -...•.................................122
Discussion of chemistry···········-······-··············-·········· 81 Definition···--·-················-···-····-··········· -•..-122
Geochronologic data for the Arabian Shield·--···-·····-··········· 84 Occurrence, thickness, and lithology··-···················-122
First radiometric age determinations, by L.T. Aldrich ..... 84 Paleontology and age.-.......••....•....•.........- 123
Early tabulation of Rb-Sr and K·Ar ages, by G.F. Brown, Jizan Group.-.-....•...•......- - -.........•.124
Carl Hedge, and Richard Marvin .-......•....-............ 87 Bathan Formation (Miocene) - -•...••...•............125
Crustal history of the Precambrian shield - -.... 93 Definition··-······-·········································-··-··125
General statement-....-....-..-- - -- -- - -.- -.. 93 Lithology and thickness -- -- -..-- 125
Early crustal history .•....- - -.....•..........-. 94 Occurrence and nature of contacts .•......................125
VII
VIII CONTENTS
Page Page
Cenozoic rocks-Continued Cenozoic igneous rocks-Continued
Bathan Formation (Miocene)---Continued The harrats-Continued
Paleontology and age------- -.•...•........•.....•....A125 Harrat Hedan------------..--..--.- -..-.--------------A158
Raghama Formation (Miocene).........•...•...•............... 125 Harrat Nawasff-al Buqnm--.-.-•..-.-.•.-.-.--.--..------- 161
Definition-··········--··---··························........... 125 Harrat ad Damm and Harrat Tuffil (Shama}-.-•..--- 161
Occurrence, thickness, and lithology····················· 126 Harrat al Birk--....•...•-.----....•.......----...------------ 161
Nature of contacts···--·········-------····················-- 126 Jabal as Sarat --- --.--.-------.- 163
Paleonotology and age...--------------..................... 127 Cenozoic history and evolution of the Red Sea •..- ------ 163
Cenozoicigneous rocks----------------------------------....•..-..-... 128 Early Tertiary setting---......................................... 163
Tertiary hypabyssal igneous rocks.•-..•-..-._.--............. 128 Continental rift-valley stage ••...••.....•....••...•.......•-..-- 163
Cenozoic basaltic lava flows--_._-_.__._-_._-_.................. 149 First-stage sea-floor spreading ..••....••....•....•------------- 165
The harrats ..........•...•••...--.-----------••---------------...... 151 Subsequent events·································-·-------------- 166
AI l,Iarra~·················································..... 151 Geomorphology------------...•.-.......••.-.-••..-..•.-..--............. 167
Harrat ar Rahah-tUwayrid---------•.-..................... 152 Cycles of erosion -----------------•.....•....•.....•...•...•......- 167
Harrat Khaybar--------------------.......................... 154 Arid cycle---------••-..•.•...••..........••...••.......•...••-- 167
Harrat Lunayyir------···································-.... 155 Common desert erosion cycle ......•••..•••.••.----------- 168
Harrat I'shara-Khirsat and Harrat Harairah.--.-..... 156 Tihamah------.••....•...•........••..........••....•-.--------------- 170
Harrat Kurama'..•--.-----------------------................. 157 Scarp mountains----.•..-......••.-..••..-- - -- ------ 172
Harrat Raha~-------------------------························· 157 Hejaz·'Asir and Hisma Plateaus.••....•.........•........•.... 174
Harrat al Kishb--------------..--..-......................... 158 Najd pediplain-------------..-...................................... 175
Harrat al Hutaymah ------.................................. 158 References cited--------------.....•......•......•...•.....•...---------- 179
ILLUSTRATIONS
(Plates are in pocket]
FRONTISPIECE. The Arabian Shield as seen from space.
PLATE 1. GeologicmapoftheSaudiArabianShield.
2. MapsofCenozoicigneous rocksofSaudiArabia.
3. Physiographicprovinces ofthe ArabianPeninsula.
4. Mapsshowingdetailsofsharms alongtheArabiancoast ofthe RedSea and theGulfof'Aqaba,SaudiArabia.
Page
FIGURE 1. IndexmapshowinglocationoftheArabianShield,ArabianPeninsula ----...•............••.....•.....••...•......•....---- A3
2. MapshowingestimatedrainfalldistributionintheArabian Peninsula----······································------------- 8
3. Photographsofexamplesofafewphreatophytes,indicatingpermanentgroundwater .••....••....••...-.--.---------.. 12
4. PhotomicrographofamygdaloidalmetabasaltattheJabalEss ophiolitecomplex........••....•..................--...... 19
5, 6. Photographs of:
5. Baish-BahahGroup··························-··----------------------------••.....•......••..........•....•...........---- 20
6. HornblenditeinterbeddedwithpinkmarbleoftheJiddah(Samran)GroupinWAdi F~timah,and
pillowlavainbasalt,Hilwaarea,onnorthwallofWadi Bayshgorge.....•.....-.-..•--.-...-.---------... 21
7. Obliqueaerialphotographshowingviewtothe northwestacrossthe AblahandJiddahGroups ...••...•..•.......•...• 23
8-13. Photographs of:
8. AblahGroup•••..-.•....••.••...•...•..---.------.----------------------.--.••....................•....•....•..------------- 25
9. FatimahGroup,northWadi Fa.timah.......••...••......••...•...•.-.................................................. 26
10. SilasiaFormationshowingsiliceoushematiteoutcropsintrudedbydiorite atWadi Sawawtn..•......••..-- 27
11. ViewnorthalongthestrikeofstrataboundgossanatWadi wassat inHalabanGroupvolcaniclastic
sediments········.•...•...•......•.....•.•-.-.-...----------......•...•••...........•.....-.,••--•.'-..--.--.-------.-. 27
12. MurdamaGroup ....•.........•.................••...••.••...•....-----------..-•..--...•.....••.....- --- 30
13. ShammarandJubaylahGroups...------.-----------------------------.-•....•.......•.....••.....•........-----------.. 32
14. Graphshowingincremental39ArKoftheJubaylahandesiteatthe typelocalityoftheJubaylahGroup ---.--...•.....- 34
15. AerialviewtothesoutheastofJabalHuassanattheeastedgeoftheshieldandphotographofJabalShayi'
layeredgabbroplutoninthesoutheasternshieldnearthevillageofKhaybar •.•.•......•....•••......------------... 35
16. Mapshowingtectonicbeltsandregions usedtodefineregionalvariations andtrendsinthechemical
dataexaminedforthisreport....•..•........•...•.....•...........-------------.-•......•........•.....•............•..------- 66
17-21. Na20-CaO-K20 diagrams showing:
17. Chemicaldistribution(molardata)ofcontrolsamplesofmetavolcanicrocks····················-·..-········--- 68
18. Chemicaldistribution(molardata)ofmetavolcanicrocksandafewdikerocksreportedinthisreport
intables3and4••............- -.- -------------•....•..-..•.-..•..--.-..•........--..•--------- -- 69
CONTENTS IX
FIGURES 19-21. Na20·CaO-K20diagrams showing: Page
19. Plutonic-rockchemistry(molardata) ofcontrolsamplesclassifiedbyage ----------------------------.---------A71
20. Plutonic-rockchemistry(molardata)ofsamplesreported inthisreportintables3and4and
classifiedbyage--------------------·--------------------------····....•-...--.••.-..•.------------------------------ 72
21. Summaryofalltheplutonic-rockchemistry(molardata)examinedforthisreport..•..-------.---------...--. 73
22-25. AFM diagrams showing:
22. Metavolcanic-rockchemistry(weightpercentdata)ofcontrolsamplesclassifiedbyage•...-•............--- 75
23. Chemical(weightpercentdata)distribution ofmetavolcanicrocksandafewdikerocksgivenin
tables3and4..•.--•.---.-----------------------------------------------------------------------------..------------- 76
24. Chemical(weightpercentdata)distributionofrocksofthedioriticsuite fromtheSaudiArabian
Shield ---------------------------------------.--.•.-------•.....-.-------.---------.------------------------------.--.. 77
25. Chemical(weightpercentdata)distributionofrocksofthegraniticsuite fromtheSaudiArabian
Shield -------.--.--.----.--......•...•.-.•..•---.-...----------..--.--...--.....--...•......••...•-•....•.....-...----- 78
26-28. Alkali-silica diagrams showing:
26. Metavolcanic-rockchemistry(weightpercentdata)ofcontrolsamplesoftheBaish-Bahahand
JiddahGroupsandoftheHalabanGroup----....-.....------------------------------------------------------... 80
27. Metavolcanic-rockchemistry(weightpercentdata)ofcontrolsamples oftheMurdama,Shammar,
andJubaylahGroups,andofthemetavolcanicrocksanalyzedforthisreport····-··················--··- 82
28. Plutonic-rockchemistry(weightpercentdata)ofdioriticsuite forsamples ofthisreportandof
controlset ----------------------------------------------------------------------------------------------------------- 84
29. Alkali-silicadiagramsshowingplutonic-rockchemistry(weightpercentdata)ofgraniticsuiteforsamplesof
controlsetandofthisreport,andhistogramshowingdistributionofK-ArandRb-Sragesforseveral
minerals.-.-.-.-..•....•....•..........-.---.---•...--.••-.....•....•..•.......••...........•....••.....•......••.......•...------ 86
30. Verticalaerialphotograph ofthenorthernportionoftheAnNimasbatholith--------------------------------------------- 96
3!. Obliqueaerial photographshowingviewtothenorthwestoforthogneissdomecontainingenfolded
amygdaloidalmetabasaltflowsoftheBaishGroup-----------------------------------------------------------------...... 97
82, 33. Photographs showing:
32. SchistosegneissatWadi Dhuqiyah65kmsoutheastofAt Ta'if••...•...•....•.....••....••.........•..--.----. 98
33. Aerialviewsouth oftheeasternedgeoftheKhamisMushaytgneissdome,andJabalalHidab.-.-.------. 99
34. Histogramsshowingresults ofgeochronologicanalysesofPaleozoicandPrecambrianrocks-------------------------· 100
35. Obliqueaerial photographofviewtothesoutheastfromlat23°05'N.,long45°05'E.neartheeastedge
oftheshield-------------------------------------------------------------------------.-.--------------..-.••.....-.--..- --. 102
36, 37. Aerial photographs of:
36. ViewtothenorthwestoftheNajdfaultzonesouthwestof'Anf....-.-.•-..••...-..----------------------------. 104
37, JabalAdhqanal'Atshan(lat22°41'N.,long44"06'E.)-....-..--------..-..---------------------------------------. 105
38. Diagramsshowingvariationsininitial81Sr/86SrandRb/Srratioswithage-----------------------------------------------. 106
39-41. Photographs of;
39. SiqSandstone-----------------------------------------------------------------.------------------.--..-----------........ 107
40. Triassic KhumsSandstone.•...•...•-...•...•...•....-•......•...-...•............••...•••.....•......- -..-------. 109
41. LimestoneoftheAmranFormation-------..--------•...----.-.---•...---------------•.------------------------------. 111
42, 43. Type sections of;
42. Amran FormationatUmm'Araj-----------------------------------------------------------------------------------... 112
43. UsfanFormationat'Usfan Pass------..-.-------- ---..-------.-.-.- - -.•......- - ----- 116
44. CompositecolumnarsectionoftheUmmHirnarFormationandoverlyingandunderlyingrocksintheJabal
UmmHimararea ..••...•.....•-...----..-.---------..--------.-----.---------------------------------------------------------- 118
45. AerialphotographsoflateriteunderAsSaratlavas---------------------------------------------------------------------..... 119
46. Typereferencedsection slightlymodifiedfromlocalityofthemeasuredShumaysiFormation....-.....•..--....----- 121
47. StratotypesectionoftheBaidFormation,nearAdDarb••.......•...-..-•.............•....•...-..---..-••.-.--------------- 123
48. Compositephotograph oftheBaidFormationatWadI Bayd...----..------------------------------------------------------. 124
49. Photographofexposureofthe BathanboulderconglomerateatWadi adDuqahintheJabalShada
quadrangle-------------------------------------------------.-------------------.....•....-....-..-.•••.....••....••...•...------ 124
50. AerialphotographoftheRaghamaFormationsoutheastofQuba···-·······-·----··--------···---------------------------- 127
5!. HistogramshowingagesofselectedTertiaryigneousrocksandglauconitefromaroundtheRedSea----------····· 129
52. Chartshowing modalanalysesofTertiarycontinentaldikesplottedonquartz-alkalifeldspar-plagioclase
diagram ---.--------.---....•...•...--.......•....•.......•....••......•.....- -.-------..------------------------------- 148
53. HarkerdiagramshowingalkaliesplottedagainstsilicaforTertiaryigneous rocks--------------------------------...... 149
54. IrvineandBaragarclassificationdiagram-----------------------------------------------...•.-...•......•...- ---..----- 150
55, 56. Ternary diagrams showing distribution of Tertiary igneous rocks from western Saudi Arabia:
55. Na20-K20-CaOternarydiagram andAFMdiagram------------------------------------- --.-.-.- -- 150
56. Normativealbite+nepheline·orthoclase-anorthite diagramandY-La·Ceternarydiagram .----------------- 151
57-60. Photographs of:
57. RupturedcrateratthecrestofHarratal'Uwayrid-----------------.--..- -•..--•.•....••.....••...•- ---- 153
58. Basalterosional frontofHarratar Rahah ..-----.•..•.......•.......•..-------------------------------------------- 153
59. EolianundercuttingofRam-UmmSahmSandstoneataNabateantomb(65A.D.)atMada'ln':;;alih----.. 154
60. HolocenecraterofwhiterhyolitetuffandlapilliofAbyad waUbayyidinHarratKhaybar-------·······-- 154