勿 D enis Vaslet U pper O rdovician glacial deposits in S a u d i A rab ia K ingdom . N ew data have been published by D G M R on the early O ne of the niaJor results of the geologic m ap- Paleozoic lithostratigraphy resulting from this w ork as 1:250 ,000- scale geologic m aps and explanatory notes (V aslet and others, 1985: M anivit and others, 1986} W illiam s and others, 1986: Ekren and oth- ers, 1987; V aslet and others, 1987), and these data have been sum - m arized in a D G M R Professional Paper (V aslet, 1989). B efore 1985, the stratigraphy ot low er Paleozoic ro c k s of Saudi A rabia w as based m ostly on the international stratigraphic lexicon (Pow ers, 1968), w hich form alized the earlier w ork ot Thralls and H asson （1956), Steineke and others （1958), and Pow ers and others (1966). In th e schem e proposed by Pow ers （1968), the early Paleozoic succession of central S aud i A rab ia w as sub divided in to tw o form a- tions (fig. 2):（I）the C am brian(?) to E arly O rdovician (A renigian) Saq Sandstone. unconform ably overlying Proterozoic Shield rocks 卷not*thive,vtern Arabia. G rap浪tolite Z,0110tiO17 ifRhU lteS and com posed of conglom eratic and coarse- to fi ne-grained sandstone th at m a n ne and siltstone; and (2) the T abuk Form ation, conform able on the Saq cla-v sedimentation began (ilier ihe ice- Sandstone, consisting of shale and sandstone and subdivided into COP M elted : bY m iddle Llundoveriun time in central seven inform al units considered to range in age from Early O rdovi- A ra b ia a nd 脚 ea吻 Llandoverian tinte in nol-th- cian (A renigian) to E arly D evonian (G edinnian). H elal（1964 , 1965) w estern A rabia . used a different term inology and restricted the Tabuk Form ation to O rdovician deposits. H e defi ned a new form ation for the Tabuk re- Updated paleofacies inaps have been inte- gion Silurian rocks, that is, the Sharaw ra form ation . H elal（1964) also con sidered th e base of the T abuk F orm atio n to b e L lanv irm an B ahafzallah and others (198 1）and A l-Laboun (1982, 1986) proposed the am putation of the upper, the D evonian, part of the Tabuk Form a- tion, that is, the Taw il M em ber of Pow ers （1968). M cC lure 门978) and Y oung (1981）w ere the f ir s t to describe glacial deposits of early Paleozoic age from central Saudi A rabia (Jal as Saqiyah). T hese deposits w ere (partly) m apped by Bram kam p and others (1963) as "brow n to tan sandstone Ithat] transgresses the low er and m iddle parts of the [Tabuk I forination, ' although they w ere not interpreted as such at that tim e. 拼萝 In 1978, M cC lure tentatively referre d t o the L ate O rdovician glaciation previously described in the Sahara (Beuf and others. 1971）although he concluded that insu什icient data w ere available. In tro d u c tio n The existence of Late O rdovician glacial environm ents w as corrobo- rated by a sedim entologic study by C lark-Low es (1980) in the Q asim E arly Paleozoic rocks in Saudi Arabia crop out in three areas。、。 region . This latter author proposed the nom enclature of the "Sarah discontinuous fringe around the Proterozoic A rabian Shield (fig. 1): m em ber" for glacial deposits that form ed part of the "T abuk Form a- (1) in the northw estern (T abuk) area extending w est from the G reat tion" defi ned by Pow ers (1968). N afud (A n N afud) to Jordan, (2) in the central area including the D etailed study of the stratig ra p h ic succession that includes these H a'il and Q asim regions in central A rabia. and (3) in the southern glacial deposits led V aslet（1987a, b. c: 1989) to recognize tw o m a- area extending from Jabal W ajid to N orth Y em en. T hese outcrops jor glacial erosional surfaces that underlie the glacial to periglacial are bounded to the north by the erosional surface beneath the U pper deposits w ithin the "T abuk Form ation" of Pow ers （1968). L ithostrati- C retaceous W asia Form ation and to the northeast and cast by the graphic evidence clearly dem onstrates the need for revision of the erosional surface beneath the U pper Perm ian K huff Form ation. U p- l ab u k F orm atio n . w hich m u st be con sidered an o bsolete u nit in view per Perm ian deposits directly overlie the eastern part of the Shield. of the internationally accepted rules of stratigraphic nom enclature. In southern A rabia, the K huff Form ation is m issing and the Paleozo- N ew I ithostratig raphic units replacing the form er "T abuk Forin a - ic is overlain directly by Jurassic deposits. tion" w ere defined and featured on the D G M R G eoscience M aps P aleozo ic ro cks of cen tral S aud i A rab ia h a ve b een stu d ied in published for the H a'il and Q asim regions, and a synthesis of the detail by the French B ureau de Recherches G 6ologiques et M inj}res currently available lithostratig raphic, sedim entologic, and biostrati- (B RG M ) as part of the Saudi A rabian D irectorate G eneral of M ineral graphic data has been sum m arized in a D G M R Professional P aper R esources' (D G M R ’s ) system atic geologic m apping program of the (V aslet, 1989 ). 如 isod cs, 饰 1. I 了．n o . 了 14 8 340 玲 军 ｜一 韶 3 8 ' 心0 0 自劝 ． 呜石． s o . 5 2 . 5 ‘． 5 6' 5 日． 6 r ｜ 戳 勺 窦 卜 es I R A Q L 2 ／ ／／ ／ 刀 Y r 犷 ／／ ／／ ／ e ／／ 刀 ／／ ／ 刀 省试 丫／ ／ 交 es 心／ ／／ ／ 簇.Xzid<v/ a}/n /// ！ 护 丫／ ／ 沁 州 ﹃哎 丈 刀 ‘j 、 ︺ 、 ．、 镶 t;4}A, 左月 P 叭 ， 甲 、 2so 口 0 ！R A N 乍 PiOiiTHWESTERN 尸 尸 I }, 几 f"iy, 产 ＋ 于 麦聋早一篷 二 0． 十 十 ． 口 了汀叮甲东 + 踢 时卜,ra cniva h 黝＋ ＋ Q d h ili t o . tif 卜 ＋ 十 ＋ ． ＋ 三书 n 几 “ 曰 孟 甘 口 2 6户 2 6 0 琳 丫 ＋十＋ ＋ 十 A 肠 石i 十 ＋ 十 ＋ 戈 男 .r x 薰飞 娜 十 十 ＋ ， 十十纂 ＋ 十 十 十 十 十 十 十 之 卜石面 熬 O m a n G u lf 4.%++撰 、 」． ＋＋．十 十 十 ＋ ＋ ＋ 气 ＋ ＋ ＋ ＋ ＋ ＋ 十 十A份.击．右 卜 R i 甘o d h 刀 夕劝户 ＋ 十 十 ＋ 十 ＋ 十 ＋ ＋ 斗 2 4 - ．．． ﹄ ＋ 十 十甘 十 ＋ ＋ ＋ 十 十 十 夕知% 溉、 ＋ ＋ ＋ ＋ C E N T R A L A R A B I几 斗 ＋ ＋ 十 十 ＋ 票咨 公 一 － ， 稀 ＋ ＋ ＋ ＋ ＋ 十 攀 口 十 ＋ 十 ＋ 十 ＋ ‘卜 、 十 十 十 十 ＋ ＋ 味 2 2 户 卜 ＋ ＋ 十 十 十 公 勺 劲一 黯 目Ub 压o n ＋ ＋ 十 十 十 泌 厂 D J id d . h ＋ ＋ 十 ＋ ft ＋ ＋ ＋ ＋ I 口 才 汾 ＋十＋尽+ A L Z 护 十 十 十 魏;.dt,. 干 ＋ 十十丫＋丫燕藻 口 SOAURTAHBEIARN 是 ， p 认\ } a 十十十十丫 犷伙迸 180 i s - 户、十，+% -Q+.,U 一‘ * 恻 , 十 ，．1 u引 饭 Forason 琴黔。： 乌 0 ． 1 宁 160 二 ， N O RT H 二创、 鹊 夕 E M E N ， In d i a n O c e a n 肠 月 叛气 (A r a b i a n s e a ) H . 'd r o ＋ ＋ ＋ 忿 ＋ 弓 协 o 护 勺 、OU楠 锐 a Y E M E N ＋ 七 + *叮 对 S - tra A D E N G u lf of A d e n 《之匕卜 12 ' 1妙 气之， ， 580﹂ 36 0 3 8 ' 4 0 ' 4 2 ' 4 4 ' 4 6 ' 4 日‘ 5 0 . 5 2 ' 5 4 ' 5 6 . F igure I一 S im plified geologic m ap of the A rabian P eninsula. 一 E X P LA N A T IO 国N O m an A llochthonous front Late Perm iant o Early Cretaceous 翌 O m an o phiolites 一Ero sion surface pre-Khuf Form ation (Late Perm ian) A 四 O m a n A uto c h tho n o u s P ale o zo ic P re - L a te P e rm ian F ig ure 2 . - H istory oj'lith ostratigraphic ＊ 囚 classification w ithin the Paleozoic 口 P ro te ro zo ic S h ie ld ro c ks succession oj Saudi A rabia and Jordan. Q u atern a ry A bbreviations: conglom ., conglom erate; 姗 J., jacies; fm ., form ation; gr., grained; Tertiary to Q uatern ary v olcanism M a in o il fie ld s in S a u d i A ra b ia 圈 夕 H am m ., H am m annyat; lim est., Ist., Late C retaceo us to Tertiary lim estone; Llandov., L landoverian; m b., 2 0 0 旧 0 O 2 0 0 月0 0 砚而 m em ber;尸recam b., P recam brian; sh., Erosion surface pre-W asia Form ation shale; sst., sandstone; Trans., (Late C retaceo us) ｝ T r a n sitio n .