Pavel Bosak (Czechoslovakia)

The Bohemian Massif represent the Epi-Variscan Platform, consolidated during the  Variscan Orogeny (Carboniferous-Permian). It consists of several  regional-geological  regions differing in the geological and paleogeographical evolution.

Karst  rocks  are predominantly of Devonian system  (Uppermost  Silurian  to Lower Carboniferous) in well diagenetic to metamorphosed state. Karst rocks  are mostly  of different limestone types, rarely dolostones. Their  max thickness is 1000m. Minor  areas are composed of Precambrian  (Proterozoic),  Ordovician  or Silurian marbles and of Jurassic limestones. Very rare are gypsum  karsts.  The structure of karst areas is mostly highly folded and block-faulted. Large  areas are  covered  by younger beds with variable thickness. The  major  karst  areas concentrated on the level of 400 to 500 m a.s.l. In the central are part of  the Bohemian  Massif. Some are occurring in marginal mountain ranges (up to  1000  m a.s.l.)  They are characterized by young development, i.e. since Miocene  uplift of marginal mountains.

The  evolution  of karst is long-terming. Two  major  karstification periodscan be distinguished: (1) pre-Cenomanian and (2) post-Santonian. It seems,  that the  main phase of karst evolution took place during  Oligo-Miocene  times (it concerns the evolution of caves as well as of some surficial forms).

The main karst type of the Bohemian Massif can be stated as dispersed  karst of  the  Central European type (as defined by Panos) occurring in  limited  area with  no  interconnection  and differing geological  setting.  The  largest  are Moravian  Karst, Bohemian Karst, very important (from evolution view point)  are Javoricko,  Mladec, North Moravian, Tisnov, Krkonose, Jested Karsts  and  minor karst regions in deeply metamorphosed regions of the Moldanubicum.  Jihomoravsky and  Stramberk  karsts are special regions incorporated  into  Outer  Carpathian Chain  (blocks  of autochthonous Jurassic limestones in frontal areas  of  flysh nappes).

Owing  to densely inhabited nature of our landscape, numerous  problems  are occurring:  agriculture,  mining (open pits and mines),  pollutions(air,  water, soil),  water  supply  from karst sources, tourism and  medical  utilization  of karst,etc.

Alfred Uchman (Poland)

The  Tatra  Mts  - highest massif in the Carpathian chain,  belongs  to  the Alpine  system.  Lengh of the main ridge is about 80 km and average width  -  17 km. The highest peak is Gerlach Mt(2655 m  a.s.l.). Arrounding  depressions are located at 850 - 1000 m a.s.l.

The  Tatra Mts consist of a central granite massif(Carboniferous)  intruding the  older  metamorphic schists, covered by mesozoic sedimentary  rocks, and of three main nappes thrusted from south at Late Cretaceous time. This nappes with complex  tectonic  building  include  old  Paleozoic  crystalline  and  Mesozoic sedimentary rocks.

During Pleistocene the mountain glaciers were formed in the Tatra Mts  above 950  m  a.s.l.  three or four times. Eastern part of  the  mountains  were  more strongly glaciated than the western one.Contemporary postglacial  landscape  of the  Tatra  Mts is the evidence for the last glacial in  the  Late  Pleistocene. Remains  of  the  older glacial forms and deposits  were  intensively  destroyed during the last glacial.

Karstification  of  the Tetra Mts. has developed mainly in  middle  Triassic limestones  and  dolomites and in Middle Jurassic-Lower  Cretaceous  limestones. The total thickness of the karstified rocks not exceed 1000 m.

Surface  karst is very poorly developed. Karrens and small bare dolinen  are seen only  in a few places. Big karst landform are absent. On  the  other  hand there  are about 480 caves with an underground karst area of about  50  km² (Fig.1).  15 of which exceed 1000 m in lengh, and 13 exceeding 100 m  in depth. The  longest cave is the Mietusia Cave (9040 m) and the deepest -Wielka  Snieza Cave (768 m deep -Fig.2)

  Speleothems  in  the  Tatra Mts are  rather  poorly  preserved.  There  are horizontal and very frequent vertical caves of gouffre and aven type. 12  levels of  horizontally developed cave galleries were distinguished,  often  connected each  other by vertical shafts .Such tiering distribution of caves is  connected with periodical deeping of the valleys .After each deeping episode the  vertical parts were formed. In the older higher levels the infillings in caves  weathered under  warm and humid climate conditions, probably during Pliocene. Four  lowest levels  less  than  80 m above valleys  bottom  contain  fluvioglacial  material deposited  during  Pleistocene. The tectonic movements had caused  the  valleys deeping during Pliocene.

Fig.1. Schematic map of the main karst region in Polish part of The tatra Mts.
1 - sedimentary rocks; 2 -crystalline rocks; 3 - main karst areas;
4 - main tectonic lines; 5 - national border.

DEVELOPMENT OF KARST DURING QUATERNARY

Differential  distribution of glaciers make non-equal pressure  on  basement and relaxation after its melting. It leads to development of deep fissures which have been used by underground circulation of water, usually very complicated and independent of  surface  system. The young tectonic movements  related  to  the relaxation of basement after melting of glaciers are probably also the cause  of dislocation  and fracturing of speleothems inside the caves.  Erosion  decreased during  glaciations  and increased during and after melting of ice  as  well  as after tectonic movements (?) causing periodical deeping of valleys. This deeping promoted the development of the four lowest cave levels. Fluvioglacial  deposits have been accumulated inside the caves by ice melting water.

Precipitation of speleothems was intensive during warm, non ice periods when infillings  of caves were partly cemented. During glacial periods  precipitation of CaCO₃ were stopped and speleothems were frequently dissoluted and  destroyed by aggressive cold water or frost in this time. Stable isotope method  research of speleothems allow to distinguish 5 periods of CaCO₃ precipitation, connected with warm periods. First period is from 140-85 ka BP,2th from 68 to 53 ka BP  , 3th  from 43 ka BP, 4th from 35 to 25 ka BP and 5th from 7 (10?) ka BP  to  the present. Glaciations were developed between 4th and 3th , and probably  between 2th and 3th period.

Fig.2 Schematic plan of the Wielka Snieza Cave(based on: Grodzicki, Kardas, 1982)

THE FACTORS FOR THE DEVELOPMENT OF THE PEAK-CLUSTER DEPRESSIONS IN THE MAOLAN KARST FOREST, GUIZHOU, CHINA

Zhou Zhengxian, Li Xingzhong (China)

The Maolan Karst Forest is located in the transition slope zone between  the south  part of the Guizhou Plateau and the Guangxi  Hill-Plain,  107° 52¢ -108° 05¢ E  and  25° 09¢ -25° 20¢ N,  with an area of 210  km²  and  average  annual temperature  of 15.3° C and precipitation of 1752mm. Typical  karst  peak-cluster depressions are widely distributed on the Carboniferous dolomite and  limestone, and the subtropical karst virgin forest are well preserved.

The  factors  in the forest-ecological environment for  the  development  of karst have been studied. They are mainly as follows:

1.  The influence of plant-roots. Vegetation-roots in the karst  forest  are well  developed.  The  boring process of the roots  caused  the  destruction  of limestone. In the peak-cluster depressions, the dense forest with high and large trees  led to the boring process stronger, and on the top of hills  with  sparse trees it is weaker.

2. The influence of soil. Soil in the foresty area with rich organic  matter and humus contains high quantity of CO₂. The humic acid in the organic  matter combines with calcium and forms compound of calcium, resulting in karstification in  the  limestone under the soil. Soil in the  depressions  is  concentratedly distributed  and contains organic matter as much as 40%, whereas on the peak  of hills  is  rare  with  only  20% of organic  matter.  It  is  evident  that  the karstification in the depressions is much stronger than on the top of hills.

3.  The  influence of mini-climate. The wide cover of virgin forest  in  the foresty area result in a different of climate-environment between the depression and the top of hills.

In the depressions with closed topography and dense forest, the sunshine is rare,  the  bryophyte  is  fluorishing and the surface  is  in  humid  condition throughout  the  year with annual humidity of 94%. However, on the peak  of  the hills,  the forest sparsely covered, the sunshine is strong and the  surface  is dry  with only 83% of the annual humidity. Obviously, the karstification in  the depressions is stronger than that on the top of the hills.

4.  The influence of precipitation and runoff. The annual  precipitation  in the  virgin forest area is 1752mm, which is 432mm more than its periphery  area. Water accumulation  of  the forest, especially the retension of  water  in  the mantle  of withered leaves and twigs, prolong the processes  of  rock-corrosion, leading  more rapid  karstification. The good condition of  catchment  and  the abundant  water quantity  in the bottom of the  depressions  result  in  strong karstification,  and the dry condition on the top of the hills causes  obviously weaker karstification.

Sui Guojun (China)

The Taizihe Basin is underlain by Cambrian-Ordovician limestone with an area of more than 1000 s.km and average annual precipitation of 1000mm.

Karst  development  in  the area was  controlled  by  geological  structure, geomorphology and climate. Many caves were developed in the area. The large cave is more than 2km long and the small one only a few meters. Development of  those caves was  controlled by the periodically uplift of the neotectonism,  causing  6 horizons of cave system (Tab.1).

Karst  water  resources in the area is rich and karst springs can  be  found everywhere with the max discharge of more than 100,000t/d.

Tab.1

TRAVERTINE FEATURE IN HUANGLONG AREA, SICHUAN, CHINA

Zhou Xulun (China)

Travertine is the most common karst feature in Huanglong area, Sichuan.  The paper deals with the travertine feature in the area.

1. Karst deposition forms and their complex model

a. Rimstone dam and "color pool". The rimstone dams are made of travertine. The  part  upstream  from the dam which is full of water is  called  the  "color pool". The "color pool" are distributed in groups on different level. The  first level  is  a  group of about 400 pools, on 3552-3569m a.s.l., and  the  other  2 groups of 300 pools on 3190-3220m a.s.l.

b.  Tufa  flowstone.   The  Huanglong  tufa  flowstone  were  formed   under precipitation of calcium carbonate in the laminar flow-water, 2500m long and 35-170m wide, which are mainly in slight yellow color.

c.   "Travertine   cascade".    Travertine   in   vertical   flow-form    is morphologically  like water-fall. The Xianshendong "travertine cascade"  is  the most famous one in Huanglong area, 33m wide and 6.7-7.2m high.

d. Back cave in "travertine cascade". The back cave is a space between  the "travertine cascade" and cliff where water was falled and formed the "travertine cascade". The one behind the Xianshen-waterfall is the famous.

In  the Huanglong area, travertine is in order of rimstone dams  and  "color pools" -----> tufa flowstone -----> and "travertine cascade". It is, therefore,  the deposition  model of travertine in the alpine region. The forming  mechanism  of the model is as follows:

                              CO₂                            rimstone dams and                  CO₂
Karst springs   ---------------------------> "color pools"     --------------------------------->
                       decreasing of temperature                             laminar flow water, decreasing
                           and pressure                                                       of water thickness

                                                      CO₂
travertine flowstone  -------------------------->  "travertine cascade"
                                 fall-flow water, increasing
                                   of flow velocity

2. Corrosion-collapse feature

Collapses  of travertine caused by corrosion are widely distributed  in  the alpine region. In the Huanglong area there are two kind  of  corrosion-collapse features.

a. Surface corrosion-collapse features in travertine

a) Karst collapse features. Collapse developed in travertine and result  in some collapse valley. In some places, the bottom of the collapse valley  reaches the underground  water level and formed collapse lake (the Xiniu  Lake and  the Baihua Lake in the Huanglong area).

b) Corrosion rimstone and spring-eyes basins

It  is  rimstone  formed on the travertine as a result of  laminar  flow  of water, which  contains some corrosion features on the bottom  of  the  rimstone pools.  Some old and hard spring-tufa in basin form remained in  the  pools  is called spring-eyes basin.

b. Corrosion-collapse caves in travertine

Some  caves were formed in the spaces between collapse blocks of  travertine after corrosion. Some of the blocks were cemented by secondary carbonate matter.

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