摘要
The Mushroom Stone Forest, which consists of granite boulders looking like mushrooms with flared sidewalls, is located in eastern Guangdong China, and is a famous scenic spot that draws many tourists each year. The Mushroom Stone Forest has been traditionally recognized as a collection of wave erosion landforms and used for the reconstruction of palaeo-sea-level changes along the coastal areas of eastern Guangdong in previous coastal researches. By combining in situ measurements of the aspect,vertical profile and height of boulder sidewalls,palaeo-coastal wave direction estimation, rock density determination, major elemental analysis, and petrographic thin section analysis, this paper presents an alternative origin for the Mushroom Stone Forest.Our results suggest that wave or wind erosion cannot offer a satisfactory explanation for the formation of the Mushroom Stone Forest; The boulders that make up the Mushroom Stone Forest originated from the corestones in the granite weathering crusts of the Little Sangpu Mountain; When the debris of the weathering crust was removed, the corestones are perched on rocky outcrops or half-buried by weathering debris beneath the natural land surface;The flared sidewall (concave vertical profile) of the boulders is a particular form developed in the foot zone of a half-buried boulder through increased chemical weathering beneath the land surface. A recent exposed half-buried boulder found in the study area provides convincing evidence to support this argument. Sea water reached the foot of the Sangpu Mountain during the Holocene transgression, but it merely provided a mechanism to erode the weathering debris from the bottom of the mushroom rocks and enhanced salt weathering that created tafoni on the boulders. These findings demonstrate that the boulders of the Mushroom Stone Forest are not sea stacks and cannot be served as a palaeo-sea-level indicator.
The Mushroom Stone Forest, which consists of granite boulders looking like mushrooms with flared sidewalls, is located in eastern Guangdong China, and is a famous scenic spot that draws many tourists each year. The Mushroom Stone Forest has been traditionally recognized as a collection of wave erosion landforms and used for the reconstruction of palaeo-sea-level changes along the coastal areas of eastern Guangdong in previous coastal researches. By combining in situ measurements of the aspect,vertical profile and height of boulder sidewalls,palaeo-coastal wave direction estimation, rock density determination, major elemental analysis, and petrographic thin section analysis, this paper presents an alternative origin for the Mushroom Stone Forest.Our results suggest that wave or wind erosion cannot offer a satisfactory explanation for the formation of the Mushroom Stone Forest; The boulders that make up the Mushroom Stone Forest originated from the corestones in the granite weathering crusts of the Little Sangpu Mountain; When the debris of the weathering crust was removed, the corestones are perched on rocky outcrops or half-buried by weathering debris beneath the natural land surface;The flared sidewall(concave vertical profile) of the boulders is a particular form developed in the foot zone of a half-buried boulder through increased chemical weathering beneath the land surface. A recent exposed half-buried boulder found in the study area provides convincing evidence to support this argument. Sea water reached the foot of the Sangpu Mountain during the Holocene transgression, but it merely provided a mechanism to erode the weathering debris from the bottom of the mushroom rocks and enhanced salt weathering that created tafoni on the boulders. These findings demonstrate that the boulders of the Mushroom Stone Forest are not sea stacks and cannot be served as a palaeo-sea-level indicator.
引文
Adebayo B(2011)Effect of textural characteristics of rock on bit Wear.AU Journal of Technology 14(4):225-252.https://doi.org/10.4028/www.scientific.net/AMR.824.86
Bisdom EBA,Stoops G,Delvigne J,et al.(1982)Micromorphology of weathering biotite and its secondary products.Pedologie 32(2):225-252.http://www.documentation.ird.fr/hor/fdi:03769
Bruthans J,Filippi M,Slavík M et al.(2018)Origin of honeycombs:Testing the hydraulic and case hardening hypotheses.Geomorphology 303:68-83.https://doi.org/10.1016/j.geomorph.2017.11.013
Bryan K(1925)Pedestal rocks in stream channels.U.S.Geological Survey Bulletin 760-D:123-128.https://doi.org/10.5962/bhl.title.45744
Chen GN(1984)Preliminary understanding of the Holocene transgression and regression in the Hanjiang and Rongjiang River deltas.Marine Science Bulletin 3(6):39-44.(In Chinese)
Chiu CF,Ng Charles WW(2014)Relationships between chemical weathering indices and physical and mechanical properties of decomposed granite.Engineering Geology 179(10):76-89.https://doi.org/10.1016/j.enggeo.2014.06.021
Dorn RI,Gordon SJ,Allen C D,et al.(2013)The role of fieldwork in rock decay research:Case studies from the fringe.Geomorphology 200(11):59-74.https://doi.org/10.1016/j.geomorph.2012.12.012
Duzgoren-Aydin NS,Aydin A,Malpas J(2002)Re-assessment of chemical weathering indices:case study of pyroclastic rocks of Hong Kong.Engineering Geology 63(1-2):99-119.https://doi.org/10.1016/S0013-7952(01)00073-4
Fang G,Li S(2014)Protection and sustainable development of geological relic resources of ancient marine erosion rock group of the Meili Lake.The Earth(7):63-66.(In Chinese)
Fuchs HL,Gerbi GP,Hunter EJ(2015)Hydrodynamic sensing and behavior by oyster larvae in turbulence and waves.The Journal of Experimental Biology 218(9):1419-1432.https://doi.org/10.1242/jeb.118562
Goldich SS(1938)A study in rock weathering.Journal of Geology 46(1):17-58.https://doi.org/10.1086/624619
Huang F,Ye C(1995)Ocean hydrology of islands off the coast of Guangdong.Guangdong Science and Technology Press,Guangzhou.pp10-77.(In Chinese)
Huang RH,Wang W(2017)Microclimatic,chemical,and mineralogical evidence for tafoni weathering processes on the Miaowan Island,South China.Journal of Asian Earth Sciences 134:281-292.https://doi.org/10.1016/j.jseaes.2016.11.023
Li P,Fang G,Huang G(1991)Holocene environment changes in Zhujiang Delta.Quaternary Sciences 11(2):130-139.(In Chinese)
Li P,Huang Z,Zhong Y,et al.(1987)The Hanjiang Delta.China Ocean Press,Beijing.pp 88-178.(In Chinese)
Li Y(1987)Study on the activity of Sangpushan fault zone.South China Seismilogical Journal 10(1):56-59.(In Chinese)
Mai B,Deng X,Xia X,et al.(2018)Column-integrated aerosol optical properties of coarse-and fine-mode particles over the Pearl River Delta region in China.Science of the Total Environment 622-623:481-492.https://doi.org/10.1016/j.scitotenv.2017.11.348
Migon P(2006)Granite Landscapes of the World.Oxford University Press,New York.pp 24-131,218-235.
Milana JP,Krohling DM(2017)First data on volume and type of deflated sediment from Southern Puna Plateau and its role as source of the Chaco Pampean loess.Quaternary International438(Part A):126-140.https://doi.org/10.1016/j.quaint.2017.03.007
Ministry of Transport of PRC(2007)Test methods of soil for higway engineering(JTG E40-2007).China Communications Press,Beijing.pp 56-66.(In Chinese)
Nesbitt HW,Young GM(1982)Early Proterozoic climates and plate motions inferred from major element chemistry of lutites.Nature 299:715-717.https://doi.org/10.1038/299715a0
Parker A(1970)An index of weathering for silicate rocks.Geological Magazine 107(6):501-504.https://doi.org/10.1017/S0016756800058581
Parsons AJ,Abrahams AD(2009)Geomorphology of Desert Environments.Second Edition,Springer,Dordrecht.p 609.
Pirazzoli PA(1986)Marine notches.In:Van de Plassche O(ed.),Sea-level Research:A Manual for the Collection and Evaluation of Data.Geo Books,Norwich.pp 361-400.
Plummer CC,McGeary D,Carlson DH(2008)Physical Geology.8th Edition,WCB/McGraw-Hill,Boston.p 326.
Price JR,Velbel MA(2003)Chemical weathering indices applied to weathering profiles developed on heterogeneous felsic metamorphic parent rocks.Chemical Geology 202(3-4):397-416.https://doi.org/10.1016/j.chemgeo.2002.11.001
Raimbault C,Duperret A,Regard V,et al.(2018)Quaternary geomorphological evolution of a granitic shore platform constrained by in situ 10Be concentrations,Penmarc’h,SWBrittany,France.Marine Geology 395(A1-A2):33-47.https://doi.org/10.1016/j.margeo.2017.09.011
RoquéC,Zarroca M,Inares R(2013)Subsurface initiation of tafoni in granite terrains-Geophysical evidence from NESpain:Geomorphological implications.Geomorphology 196(9):94-105.https://doi.org/10.1016/j.geomorph.2012.06.015
Ruxton BP(1968)Measures of the degree of chemical weathering of rocks.Journal of Geology 76(5):518-527.https://doi.org/10.1086/627357
Sanjurjo Sánchez J,Alves C,RomaníJRV(2016)Assessing the weathering of granitic stones on historical urban buildings by geochemical indices.Earth Sciences Research Journal 20(3):F1-F13.https://doi.org/10.15446/esrj.v20n2.49560
Scarciglia F,Critelli S,Borrelli L,et al.(2016)Weathering profiles in granitoid rocks of the Sila Massif uplands,Calabria,southern Italy:New insights into their formation processes and rates.Sedimentary Geology 336:46-67.https://doi.org/10.1016/j.sedgeo.2016.01.015
Shantou local records compilation committee of Guangdong Province(1999)Shantou City Records,Book One.Xinhua Publishing House,Beijing.p 370.(In Chinese)
Sueoka T,Lee IK,Huramatsu M,et al.(1985)Geomechanical properties and engineering classification for decomposed granite soils in Kaduna District,Nigeria.Proc.First International Conference on Geomechanics in Tropical Lateritic and Saprolitic Soils,Brasilia.pp 175-186.https://doi.org/10.1016/0148-9062(86)91689-X
Sun H,Nelson M,Chen F,et al.(2009)Soil mineral structural water loss during loss on ignition analyses.Canadian Journal of Soil Science 89(5):603-610.https://doi.org/10.1002/9780470015902.a0025180
Trenhaile AS(2016)Modelling coastal notch morphology and developmental history in the Mediterranean.GeoResJ 9-12:77-90.https://doi.org/10.1016/j.grj.2016.09.003
Trenhaile AS,Pepper DA,Trenhaile RW,et al.(1998)Stacks and notches at Hopewell rocks,New Brunswick,Canada.Earth Surface Processes and Landforms 23(11):975-988.https://doi.org/10.1002/(SICI)1096-9837(1998110)23:11%3C975::AID-ESP916%3E3.0.CO;2-K
Twidale CR,Romani JRV(2005)Landforms and Geology of Granite Terrains.Taylor&Francis,London.pp 81-107,173-257.
Undu O,Tugrul A(2011)The influence of weathering on the engineering properties of Dunites.Rock Mechanics and Rock Engineering 45(2):225-239.https://doi.org/10.1007/s00603-011-0174-1
Wang W,Huang R(2018)3uangdong,China.Quaternary Sciences 38(2):427-448.(In Chinese)
Wang W,Wu Z(2010)Coastal dune rock development and Holocene climate changes in South China.Journal of Geographical Sciences 20(3):469-480.https://doi.org/10.1007/s11442-010-0469-2
Wang Y,Peng C,Li Y,et al(1990)The query of the age formed by Rongjiang Rift and traces of sea erosion at Liantang.South China Seismological Journal 10(1):56-59.(In Chinese)
Xu G(1994)Salt mist content and distribution in the lower atmosphere along the coast of China.Environmental Technology 03:1-7.(In Chinese)
1) Guangdong Metallurgical and Geological Exploration Team No. 931, 1982. Geological Map of Eastern Guangdong 1:200000.