广西岩溶景观特征及其形成演化分析

Characteristics and Formation and Evolution Analysis of the Karst Landscape of Guangxi

关键词:  岩溶景观  形成演化分析  流域岩溶景观带  岛链式  广西

Key words:  karst landscape  analysis of formation and evolution  drainage basins landscape zone  island chain  Guangxi

摘要:

广西岩溶景观主要分布于桂东北、桂中、桂西北和桂西南地区，有峰丛、峰林、孤峰、丘陵、天生桥、石林、象形山、崖壁、洞穴及各类洞穴次生化学沉积物、地下河、穿洞、洼（谷）地、漏斗、坡立谷、盆地、地表河、峡谷、天坑、天窗、竖井、瀑布、泉、湖泊、湿地等类型齐全、形态典型的岩溶景观，囊括所有岩溶景观的类型。它们主要以中上寒武统至中三叠统的碳酸盐岩为物质基础，首先以地表河流域（如红水河、柳江、漓江等）为主线，其次以岩溶地貌区划特征为区域划分标准，然后以所处行政区和所处流域位置（如上、中、下游）为辅线，呈线状有序、集中分布于各典型岩溶景观区及岩溶景区/公园/景点内。它们或以峰丛-峰林，或以岩溶风景河段，或以天坑群，或以地下河天窗群，或以峰丛平原，或以洞穴，或以天生桥，或以跨国瀑布等为核心，组合成多个特色突出，形态优美、珍稀、雄伟、典型，且类型齐全的流域岩溶景观带，并形成独具广西特色的"岛链式"岩溶景观分布格局。它们是全球亚热带岩溶地貌及景观典型集中发育区和杰出范例，是目前世界上展现塔状峰丛-峰林、锥状峰丛、高峰丛深洼地、峰林/孤峰平原、洞穴、天坑、天窗、地下河、天生桥、岩溶风景河段、瀑布、崖壁等岩溶景观美景最杰出的代表地，堪称全球"洞穴天坑之窗，地下河天窗之王，天生桥瀑布之奇，风景河段之美，峰丛峰林之魂"。同时，自晚三叠世以来，广西各区域（即各岩溶孤岛）的碳酸盐岩地层相继出露地表，分别进入各自的岩溶地貌/景观形成演化时代，历经自上而下或自下而上等不同方向、不同时期、不同区域的岩溶过程，分别形成峰丛-峰林、地下河洞穴、天坑-天窗-天生桥等各类典型的岩溶景观；并按时间序列和区域分异特征，以广西各岩溶区以及它们内部各岩溶地带相互之间水力联系的演变及区域地壳的间歇性隆升为时间界限和主线，将广西岩溶的形成演化过程划分为初始阶段（晚三叠世以来，碳酸盐岩地层出露，不同岩溶区始于不同地质时期）→雏形阶段（分轴型离散岛屿式成景过程，不同岩溶区始于不同地质时期）→重要发育阶段（主轴型离散岛屿式，不同岩溶区始于不同地质时期；集合型岛屿式成景过程，中更新世中晚期至全新世）→现代岩溶阶段（全新世以来至今）等4大成景阶段，分别表现出不同的成景过程、特征和机制，总体可概括为分轴型、主轴型、离散型、集合型等4种岛屿式成景机制，并将其成景模式归纳为"岛链式成景模式"。

Abstract:

The karst landscape mainly distributed in northeast,central,northwest and southwest parts of Guangxi.There is a complete range of karst landscapes in a typical shape,such as peak forests,peak clusters,isolated peaks,hills,natural bridges,stone forests,pictographic mountains,cliffs,caves and various types of cave secondary chemical deposits,underground rivers,light-through caves,depressions (valley),dolines,poljes,basins,surface rivers,gorges,tiankengs,natural sylights,shafts,waterfalls,springs,lakes,and wetland,which cover all types of karst landscapes.They mainly use the carbonate rocks of the Middle and Upper Cambrian to the Middle Triassic as the material basis. Firstly the drainage basins of surface rivers (Red River,Liu River,and Li River etc) are taken as principal lines,and karst landscape regional features as standards for zoning secondly,then administrative divisions and the locations to drainage basins (upper reach,middle reach and lower reach) as subordinate line.The karst landscapes are distributed orderly and concentrated in various typical karst scenic spots/parks. All of them are characterized by different core features,like peak forest-peak cluster,karst-landscape river section,tiankeng group,natural sylight group of underground rivers,peak-cluster plains,caves,natural bridges,cross-border waterfalls and so on.It combines a variety of karst landscapes with distinctive features,rare,majestic,typical,and complete types,and forms a "island-chain" karst landscape distribution pattern with unique characteristics in Guangxi.Guangxi karst landscape is the global subtropical karst landforms and typical concentrated development areas of the landscape and outstanding examples. It is the most typical representative for presenting tower-like peak cluster-peak forest,cone peak cluster,high peak cluster-deep depression,peak forest/isolated peak-plain,cave,tiankeng,natural sylight,underground river,natural bridge,karst-landscape river section,waterfall,cliff wall and so on. It could be admired as window for cave and tiankeng,king for underground natural sylight,marvel for natural bridge and waterfall,beauty for karst-landscape river section and soul for peak cluster and peak forest.At the same time,since the Late Triassic,the carbonate strata in various regions of Guangxi (that is,each karst island) have successively exposed the surface,respectively entering their respective karst landform/landscape formation and evolution times,from top to bottom or bottom down.The karst processes in different directions,different periods and different regions and forms peak plexus-peak forest,underground river cave,tiankeng-skylight-Tianshengqiao and other typical karst landscapes.According to time series and regional features,taking Guangxi karst areas and their internal hydraulic relationships evolution as well as regional crust intermittent uplift as time line to classify the formation and evolution of Guangxi karst into 4 periods:Preliminary period (the exposure of carbonate rocks since late Triassic,different karst areas started at different geologic time) → rudiment period (split-axle discrete-island landscape formation,different karst areas started at different geologic time)→important developing period (main-axle discrete-island landscape formation,different karst areas started at different geologic time; concentrated-island landscape formation,middle-late mid Pleistocene to Holocene)→modern karst period (since Holocene),the different landscape formation process,features and mechanism are reflected. The overall can be summarized as four types of island-type framing mechanisms,such as split-axis type,main-axis type,discrete type and collective type,and the scene-forming mode is summarized as "island chain style mode".