Evolution of Early Palaeozoic Carbonate Platform, South Qinling Mt.
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摘要: 南秦岭早古生代碳酸岩台地属于扬子板块北部被动大陆边缘。台地经历了３个演化阶段：①下—中寒武统缓坡沉积阶段；②中寒武统—下奥陶统镶边陆棚沉积阶段；③中—上奥陶统混合陆棚沉积阶段。下志留统的进积陆源碎屑沉积淹没了全区。从台地相带的展布规律和古地理轮廓推测，早古生代时台地北侧可能存在一个已消失了的古陆。Abstract: Early Palaeozoic carbonate platform of South Qinling Mt. was developed on the north passive mar-gin of the Yangtze plate. Cambrian and Ordovician carbonate stratigraphy, more than 2000 metres inthickness, is outcropped between Shanyang-Fengzhen Fault and Ningshan-Baihe Fault(Fig. 1).Fiv a fu-ties associations are recogrrized, including anoxic /dysaerobic facies association(A1)，deeper ramp /slopefacies association(A 2)，Shoal facies association(A3)，lagoon and tidal}lat facies association(A 4) andmixed shelf facies association(Fig. 2)·Evolution of the carbonate platform is divided into three phases(Fig.3).Middle Cambrian-Early Ordovician rimmed shelf phase is characterised by oc currence of asouth edge builtup of shoal facies association up to 500 metres in thickness and a south slope of nodularlim es tone,micritic limestone, clay shale and breccias. Inner platform deposits are composed of cyclic la-goonal massive dolostone and laminated dolostone, recording small-scale sea-level changer. Evident fallin sea level resulted from tectonic uplift led to existence of late Early Ordovician palaeokarst and karstconglomerates, which are cupped by Middle-Late Ordovician mixed shelf facies association of the thirdphase containing a transgressive and regressive cyde.Horizontal distributinn of facies zones proves lee side of platform northward and wind side sonth-w ard. It als oimpli esprobably submergedthat there was a possible ancient land on north side of platform(Fig.4)，but it wasunder Shanyang-Fengzhen Fault afterwards.
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Key words:
- carbonate platform /
- paleogeography /
- early paleozoic /
- Qinling mountains
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[1] 1 刘印环.王建平.张海清.杜风军.河南的寒武系和奥陶系.北京:地质出版社.1991.
2 李晋僧.曹宣铎.杨家禄.秦岭显生宙古海盆沉积和演化史.北京:地质出版社.1994.
3 李署光.Hart H R.郑双根.中国华北、华南陆块碰撞时代的衫一钦同位素年龄证据.中国科学B辑.1989, ( 3): 312一319
4 杨家录.东秦岭寒武纪构造古地理概况.地球科学一中国地质人学学报.1988, 13 ( 5): 473- 480.
5 张国伟等.秦岭造山带的形成与演化.西安:西北人学出版社.1988.
6 张秋生.朱永正.东秦岭古生代蛇绿岩套.长春地质学院学报.1984. 31-13
7 Ass ereto R L A M and Kendall C G Nature. origin and clas-sification of peritidal tepee structures arrl related brecdas.Sedimentology, 1977, 24 153- 210
8 Barnaby R Jand Read,J F. Carbonate ramp to rimmed shelfevolution Lower to Middle Cambrian continental marginVirginia Appelachians. Geol Soc Am Bulh 1990, 102 391一404
9 Bove,J A and Head,J F. Incipiently drowned fades within acyclic peritidal ramp serluence, L,arly Ordovician Chepul-tupec inten-al, Virginia Appalachians. Geol Soc Am Bull, 1987, 98 714-727.
10 Burchette T P and Wright V P. Carbonate ramp depositionalsystems. Sedimentary Geology, 1992, 79 3-57.
11 Gewthorpe R L.Sedimentation during carbonate rarmpo-slope evolution in a teckonically active area Bowland Basin(Dinantian).N England Sedimentology, 1986, 33 185-206.
12 Leggett,J K, McKerrow W S. Cocks L RM andRishards RB J Geol Soc London, 1981, 138 167- 176.Mulli ns H T. N eumann A C: and冷ardrnan M K. Nodularcarbnnate Sefhment onnBahamian slopes Possiblesors to nodular limestone J Sediment Petrol, 1980,5 117一131.
14 Read J F.Georntry fades and development of Middle Or-dovidan carbonate buildups, Virginia Appalachians. Bull 1982b. 66 189- 201.
15 Read,J F Carbonate platform fades models. Bull Am AssocPetGeol, 1985, 69 1-21.
16 Selg M. Origin of peritidal carbonate cycles Larly Cambri-an, Sardinia. Sedimentary Geology, 1988, 59 115- 124.
17 W ikon,J L. Carbonate fades in geologic history. Springer-V erlag, N ew Y ork, N Y.1975. -
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