Sedimentary Successions and Environments of the Late Ordovician Wenchang Formation in Tonglu, Zhejiang

FAN Dai-du; LI Cong-xian; CAI Jin-gong; DENG Bing; LUO Zhang

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Article Navigation > Acta Sedimentologica Sinica > 2003 > 21(2): 247-254

FAN Dai-du, LI Cong-xian, CAI Jin-gong, DENG Bing, LUO Zhang. Sedimentary Successions and Environments of the Late Ordovician Wenchang Formation in Tonglu, Zhejiang[J]. Acta Sedimentologica Sinica, 2003, 21(2): 247-254.

Citation:

FAN Dai-du, LI Cong-xian, CAI Jin-gong, DENG Bing, LUO Zhang. Sedimentary Successions and Environments of the Late Ordovician Wenchang Formation in Tonglu, Zhejiang[J]. Acta Sedimentologica Sinica, 2003, 21(2): 247-254.

Sedimentary Successions and Environments of the Late Ordovician Wenchang Formation in Tonglu, Zhejiang

1.
Laboratory of Marine Geology, Tongji University, Shanghai 200092;
2.
Hangzhou Institute of Petroleum Geology, Hangzhou 310023

Received Date: 2002-03-05
Rev Recd Date: 2002-08-06
Publish Date: 2003-06-10

Abstract

The Late Ordovician Wenchang Fm. is subdivided into two members. Member I (M I, the lower section), characterized by presence of thick massive sandstone layers intercalated with thin mudstone layers and brachiopodous, bryozoan and crinoidea assemblage, is interpreted as nearshore to shallow-marine deposits. Member Ⅱ(M Ⅱ, the upper section), is further subdivided two parts: M Ⅱ-1 (the lower one), consisting of sandstone intercalated with conglomerate lenses; M Ⅱ-2 (the upper section), composed of muddy sandstone or sandy mudstone with well-developed tidal bedding. There are two opposite opinions concerning the sedimentary environment of M Ⅱ. Some consider that M Ⅱ-1 is debris-flow deposits on the basin slope owing to biological assemblage containing graptolite, and M Ⅱ-2 is deep-water internal-tide deposits. Others interpret M Ⅱ-1 as near-shore subaqueous channel deposits based on its biological assemblage dominated by shallow-water species and conformity contact with the underlying M Ⅰ in the region, and M Ⅱ-2 as tidal-flat deposits. M Ⅱ-2 is characterized by alternations of sand and mud laminae, and of sand- and mud-dominated layers. In this study, raindrop imprints were observed on some bedding-planes, exhibiting the periodic subaerial exposure of sedimentation facies. The presence of symmetrical oscillation ripples shows wave activities were common at the study area. Mud pebbles are inferred to form on the intertidal flats during storms in comparison with studies on the modern tidal flats margining the Changjiang Delta. M Ⅱ-2 is, therefore, not deep-water internal-tide deposits but normal tidal-flat deposits with strong storm influence. The sand-dominated layers (SDL), several to several tens of cm thick, are interpreted as storm deposits based on the presence of: 1) scour features, 2) numerous intraformation mud-pebbles, 3) oscillation ripples, 4) relatively thick sand laminae at the lower part with an upward trend of thinning toward the adjacent mud-dominated layer. The mud-dominated layers (MDL), consisting of thin sand/mud alternating laminae, deposit after storms when sedimentary environments return to tidal regime. A small sequence, consisting of a SDL and a MDL, is thus a storm succession. Facies transition is gradual among the three units of the formation (M I, M Ⅱ-1,M Ⅱ-2). Dip directions and angles are close to each other. Detrital composition analyses show that they have similar provenance from the Cathaysian Block. It is inferred that sedimentary environments should have no much change during deposition of three different units. Sedimentological study suggested a shallowing-upward progradational succession from high-energy shallow-marine deposits to low-energy tidal-flat deposits. Upward increases of clay content indicate that sedimentary environments get closer to the shoreline. M Ⅱ-1, interlayered between neritic facies and tidal-flat deposits, is thus interpreted nearshore facies with conglomerate layers of event subaqueous channel deposits.
- tidal rhythmites,
- storm deposits,
- conglomerates,
- sedimentary succession,
- Late Ordovician,
- Zhe-Wan Marginal Sea Basin

References

[1]	浙江省区测队.1:20万建德幅区域地质矿产调查报告[R].杭州:浙江省地质局,1965[RGSZP(Regional Geological Survey of Zhejiang Province). Report of regional geology and mineral resources in Jiande of Zhejiang Province [R]. Hangzhou: Zhejiang Geological Bureau, 1965]
[2]	浙江省区测队.1:20万临安幅区域地质矿产调查报告[R].杭州:浙江省地质局,1967[RGSZP.Reportof regionalgeology andmineral resources in Lin'an of Zhejiang Province[R]. Hangzhou: Zhejiang Geological Bureau,1967]
[3]	浙江省区域地层编写组.华东地区区域地层表浙江省分册[M].北京:地质出版社,1979[Cormpiling group ofthe regional stratigraphy of Zhenjiang Province. Zhejiang fascicule of the regional stratigraphy in East China [M]. Beijing: Geological Publishing House, 1979]
[4]	罗璋,葛凡凡.浙江省上震旦统、下古生界沉积环境及相分析[J].浙江石油地质,1982,(1):12～17[Luo Z.Ge H H Sedimentary environment and facies of the Upper Sinian and Lower Paleozoic in Zhejiang Province, China [J]. Zhejiang Petroleum G-eology, 1982, (1): 12～17]
[5]	浙江省地质矿产局.浙江省区域地质志[M].北京:地质出版社,1989 [ ZGB (Zhejiang Geological Bureau). The chronicle of Zhejiang geology [M]. Beijing: Geological Publishing House, 1989]
[6]	俞国华(主编).浙江省岩石地层[M].武汉:中国地质大学出版社,1996 [Yu G H(editor). Stratigraphy (lithostratic) of Zhejiang Province [M]. Wuhan: China University of Geosciences Press, 1996]
[7]	鞠天吟.对苏杭地区早古生代地层的认识(苏杭扬子-江南型沉积过渡区的特征)[J].地层学杂志,1979,3(4):294～303[JuT Y.Cognition of the Early Paleozoic Group in the Su-Hang region[J]. Journal of Stratigraphy, 1979, 3(4) :294～303]
[8]	高振中.深水牵引流沉积-内潮汐、内波和等深流沉积研究[M].北京:科学出版社,1996[Gao Z Z.Deep-water tractive current deposits-The study of internal-tide, internal-wave, and contour current deposits[M]. Beijing: Science Press, 1996]
[9]	何幼斌,高振中,李建明等.浙江桐庐晚奥陶世内潮汐沉积[J].沉积学报,1998,16(1):1～7[HeYB,GaoZZ,Li JM,et al.Internaltide deposits of the Late Ordovician in Tonglu, Zhejiang [J]. Acta Sedimentologica Sinica, 1998, 16(1) :1～7]
[10]	周名魁,王汝植,李志明等.中国南方奥陶志留纪岩相古地理与成矿作用[M].北京:地质出版社,1993[Zhou M K,Wang R Z,Li Z M. Ordovician to Silurian lithofacies, paleogeography and mineralization in South China [M]. Beijing: Geological Publishing House,1993]
[11]	李从先,张桂甲,李铁松.潮坪沉积的韵律性与作用因素的周期性[J].沉积学报,1995,13(增):71～77[Li C X,Zhang G L Li T S.Rhythms of tidal flat sedimentation and cyclicity of affecting factors [J]. Acta Sedimentologica Sinica, 1995, 13(Supp. ): 71～77]
[12]	罗璋.浙江桐庐于潜上骆家上奥陶统浊积岩[J].浙江地质,1990,6(1):20 ( 29 [Luo Z. Upper Ordovician turbidite in Yuqian County,Zhejiang Province [J]. Zhejiang Geology, 1990, 6(1): 20～29]
[13]	王鸿祯.中国古地理图集[M].北京:地图出版社,1985[WangHZ.Atlas of the palaeogeography of China [M]. Beijing: Cartographic Publishing House, 1985]
[14]	夏邦栋,吕洪波.浙西皖南晚奥陶世复理石的沉积环境,兼谈鲍马层序应用问题[J].沉积学报,1988,6(4):44～51[Xia B D,Lu H B. A study on the environment of Upper Odoovician Flysch in western Zhejiang and southern Anhui provinces and a short comment on the application of Bouma' s sequence [J]. Acta Sedimentologica Sinica,1988, 6(4): 44～51]
[15]	蔡进功,李从先.浙西桐庐县桐君山下志留系安吉组风暴沉积[J].同济大学学报,1990,18(3):363～372[Cai J G,Li C X.Storm deposition of Anji Formation of Silurian, Tonglu County, Tongjun Hill,Western Zhejiang Province[J]. Journal of Tongji University, 1990,18(6):363～372]
[16]	冯增昭(主编).沉积岩石学[M].北京:石油工业出版社,1994.[Feng Z Z.Sedimentary Petrology(Second edition) [M]. Beijing:Petroleum Industry Press, 1994]
[17]	余素玉,何镜宇.沉积岩石学[M].武汉:中国地质大学出版社,1989[Yu S Y, He J Y. Sedimentary Petrology [M]. Wuhan: China University of Geosciences Press, 1989]
[18]	李从先,汪品先.长江晚第四纪河口地层学研究[M].北京:科学出版社,1998.[Li C X,WangPX.LateQuaternary stratigraphy of the Yangtze Delta [M]. Beijing: Science Press, 1998]
[19]	Li C X, Wang P, Fan D D. et al. Open-coast intertidal deposits and the preservation potential of individual lamina: a case study from Eastcentral China [J]. Sedirmentology, 2000, 47:1 039～1 051
[20]	Fan D D, Li C X. Rhythmic deposition on mudflats in the mesotidal Changjiang estuary, China [J]. Journal of Sedimentary Research,2002, in press

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通讯作者: 陈斌, bchen63@163.com

1.
沈阳化工大学材料科学与工程学院沈阳 110142

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Sedimentary Successions and Environments of the Late Ordovician Wenchang Formation in Tonglu, Zhejiang

1. Laboratory of Marine Geology, Tongji University, Shanghai 200092;

2. Hangzhou Institute of Petroleum Geology, Hangzhou 310023

Received Date: 2002-03-05

Rev Recd Date: 2002-08-06

Publish Date: 2003-06-10

Key words:

Abstract: The Late Ordovician Wenchang Fm. is subdivided into two members. Member I (M I, the lower section), characterized by presence of thick massive sandstone layers intercalated with thin mudstone layers and brachiopodous, bryozoan and crinoidea assemblage, is interpreted as nearshore to shallow-marine deposits. Member Ⅱ(M Ⅱ, the upper section), is further subdivided two parts: M Ⅱ-1 (the lower one), consisting of sandstone intercalated with conglomerate lenses; M Ⅱ-2 (the upper section), composed of muddy sandstone or sandy mudstone with well-developed tidal bedding. There are two opposite opinions concerning the sedimentary environment of M Ⅱ. Some consider that M Ⅱ-1 is debris-flow deposits on the basin slope owing to biological assemblage containing graptolite, and M Ⅱ-2 is deep-water internal-tide deposits. Others interpret M Ⅱ-1 as near-shore subaqueous channel deposits based on its biological assemblage dominated by shallow-water species and conformity contact with the underlying M Ⅰ in the region, and M Ⅱ-2 as tidal-flat deposits. M Ⅱ-2 is characterized by alternations of sand and mud laminae, and of sand- and mud-dominated layers. In this study, raindrop imprints were observed on some bedding-planes, exhibiting the periodic subaerial exposure of sedimentation facies. The presence of symmetrical oscillation ripples shows wave activities were common at the study area. Mud pebbles are inferred to form on the intertidal flats during storms in comparison with studies on the modern tidal flats margining the Changjiang Delta. M Ⅱ-2 is, therefore, not deep-water internal-tide deposits but normal tidal-flat deposits with strong storm influence. The sand-dominated layers (SDL), several to several tens of cm thick, are interpreted as storm deposits based on the presence of: 1) scour features, 2) numerous intraformation mud-pebbles, 3) oscillation ripples, 4) relatively thick sand laminae at the lower part with an upward trend of thinning toward the adjacent mud-dominated layer. The mud-dominated layers (MDL), consisting of thin sand/mud alternating laminae, deposit after storms when sedimentary environments return to tidal regime. A small sequence, consisting of a SDL and a MDL, is thus a storm succession. Facies transition is gradual among the three units of the formation (M I, M Ⅱ-1,M Ⅱ-2). Dip directions and angles are close to each other. Detrital composition analyses show that they have similar provenance from the Cathaysian Block. It is inferred that sedimentary environments should have no much change during deposition of three different units. Sedimentological study suggested a shallowing-upward progradational succession from high-energy shallow-marine deposits to low-energy tidal-flat deposits. Upward increases of clay content indicate that sedimentary environments get closer to the shoreline. M Ⅱ-1, interlayered between neritic facies and tidal-flat deposits, is thus interpreted nearshore facies with conglomerate layers of event subaqueous channel deposits.

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Reference (20)

[1]	浙江省区测队.1:20万建德幅区域地质矿产调查报告[R].杭州:浙江省地质局,1965[RGSZP(Regional Geological Survey of Zhejiang Province). Report of regional geology and mineral resources in Jiande of Zhejiang Province [R]. Hangzhou: Zhejiang Geological Bureau, 1965]
[2]	浙江省区测队.1:20万临安幅区域地质矿产调查报告[R].杭州:浙江省地质局,1967[RGSZP.Reportof regionalgeology andmineral resources in Lin'an of Zhejiang Province[R]. Hangzhou: Zhejiang Geological Bureau,1967]
[3]	浙江省区域地层编写组.华东地区区域地层表浙江省分册[M].北京:地质出版社,1979[Cormpiling group ofthe regional stratigraphy of Zhenjiang Province. Zhejiang fascicule of the regional stratigraphy in East China [M]. Beijing: Geological Publishing House, 1979]
[4]	罗璋,葛凡凡.浙江省上震旦统、下古生界沉积环境及相分析[J].浙江石油地质,1982,(1):12～17[Luo Z.Ge H H Sedimentary environment and facies of the Upper Sinian and Lower Paleozoic in Zhejiang Province, China [J]. Zhejiang Petroleum G-eology, 1982, (1): 12～17]
[5]	浙江省地质矿产局.浙江省区域地质志[M].北京:地质出版社,1989 [ ZGB (Zhejiang Geological Bureau). The chronicle of Zhejiang geology [M]. Beijing: Geological Publishing House, 1989]
[6]	俞国华(主编).浙江省岩石地层[M].武汉:中国地质大学出版社,1996 [Yu G H(editor). Stratigraphy (lithostratic) of Zhejiang Province [M]. Wuhan: China University of Geosciences Press, 1996]
[7]	鞠天吟.对苏杭地区早古生代地层的认识(苏杭扬子-江南型沉积过渡区的特征)[J].地层学杂志,1979,3(4):294～303[JuT Y.Cognition of the Early Paleozoic Group in the Su-Hang region[J]. Journal of Stratigraphy, 1979, 3(4) :294～303]
[8]	高振中.深水牵引流沉积-内潮汐、内波和等深流沉积研究[M].北京:科学出版社,1996[Gao Z Z.Deep-water tractive current deposits-The study of internal-tide, internal-wave, and contour current deposits[M]. Beijing: Science Press, 1996]
[9]	何幼斌,高振中,李建明等.浙江桐庐晚奥陶世内潮汐沉积[J].沉积学报,1998,16(1):1～7[HeYB,GaoZZ,Li JM,et al.Internaltide deposits of the Late Ordovician in Tonglu, Zhejiang [J]. Acta Sedimentologica Sinica, 1998, 16(1) :1～7]
[10]	周名魁,王汝植,李志明等.中国南方奥陶志留纪岩相古地理与成矿作用[M].北京:地质出版社,1993[Zhou M K,Wang R Z,Li Z M. Ordovician to Silurian lithofacies, paleogeography and mineralization in South China [M]. Beijing: Geological Publishing House,1993]
[11]	李从先,张桂甲,李铁松.潮坪沉积的韵律性与作用因素的周期性[J].沉积学报,1995,13(增):71～77[Li C X,Zhang G L Li T S.Rhythms of tidal flat sedimentation and cyclicity of affecting factors [J]. Acta Sedimentologica Sinica, 1995, 13(Supp. ): 71～77]
[12]	罗璋.浙江桐庐于潜上骆家上奥陶统浊积岩[J].浙江地质,1990,6(1):20 ( 29 [Luo Z. Upper Ordovician turbidite in Yuqian County,Zhejiang Province [J]. Zhejiang Geology, 1990, 6(1): 20～29]
[13]	王鸿祯.中国古地理图集[M].北京:地图出版社,1985[WangHZ.Atlas of the palaeogeography of China [M]. Beijing: Cartographic Publishing House, 1985]
[14]	夏邦栋,吕洪波.浙西皖南晚奥陶世复理石的沉积环境,兼谈鲍马层序应用问题[J].沉积学报,1988,6(4):44～51[Xia B D,Lu H B. A study on the environment of Upper Odoovician Flysch in western Zhejiang and southern Anhui provinces and a short comment on the application of Bouma' s sequence [J]. Acta Sedimentologica Sinica,1988, 6(4): 44～51]
[15]	蔡进功,李从先.浙西桐庐县桐君山下志留系安吉组风暴沉积[J].同济大学学报,1990,18(3):363～372[Cai J G,Li C X.Storm deposition of Anji Formation of Silurian, Tonglu County, Tongjun Hill,Western Zhejiang Province[J]. Journal of Tongji University, 1990,18(6):363～372]
[16]	冯增昭(主编).沉积岩石学[M].北京:石油工业出版社,1994.[Feng Z Z.Sedimentary Petrology(Second edition) [M]. Beijing:Petroleum Industry Press, 1994]
[17]	余素玉,何镜宇.沉积岩石学[M].武汉:中国地质大学出版社,1989[Yu S Y, He J Y. Sedimentary Petrology [M]. Wuhan: China University of Geosciences Press, 1989]
[18]	李从先,汪品先.长江晚第四纪河口地层学研究[M].北京:科学出版社,1998.[Li C X,WangPX.LateQuaternary stratigraphy of the Yangtze Delta [M]. Beijing: Science Press, 1998]
[19]	Li C X, Wang P, Fan D D. et al. Open-coast intertidal deposits and the preservation potential of individual lamina: a case study from Eastcentral China [J]. Sedirmentology, 2000, 47:1 039～1 051
[20]	Fan D D, Li C X. Rhythmic deposition on mudflats in the mesotidal Changjiang estuary, China [J]. Journal of Sedimentary Research,2002, in press

Sedimentary Successions and Environments of the Late Ordovician Wenchang Formation in Tonglu, Zhejiang

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