COBISS: 1.01 LITHOLOGICAL AND MORPHOLOGICAL CHARACTERISTICS AND ROCK RELIEf Of THE LAO HEI GIN SHILIN-STONE fOREST (LUNAN, SW CHINA) LITOLOŠKE IN MORfOLOŠKE ZNAČILNOSTI TER SKALNI RELIEf LAO HEI GIN KAMNITEGA GOZDA (LUNAN, JZ KITAJSKA) Martin KNEZ1 & Tadej SLABE1 Abstract UDC 551.435.8(510) Martin Knez & Tadej Slabe: Lithological and morphological characteristics and rock relief ofthe Lao Hei Gin shilin-stone forest (Lunan, SW China) Te Lao Hei Gin stone forest is yet one more of the diverse and famed Lunan stone forests created from subcutaneous karren. Te initial morphogenesis of the stone pillars started along al-most horizontal bedding planes and mostly sub-vertical faults and cracks already covered by thick layers of sediments and soil. Te forest’s stone pillars stand individually or in groups. Te dominant and most characteristic shape of the pillars is mushroom-like, with alternating lithological characteristics of the carbonate beds expressed in a vertical direction. key words: Lunan shilin-stone forests, lithology, rock relief, morphogenesis, SW China. Izvleček UDK 551.435.8(510) Martin Knez & Tadej Slabe: Litološke in morfološke značilnosti ter skalni relief Lao Hei Gin kamnitega gozda (Lunan, JZ Kitajska) Lao Hei Gin kamniti gozd je še eden izmed raznovrstnih in znamenitih lunanskih kamnitih gozdov, ki so nastali iz podtalnih škrapelj. Inicialna morfogeneza kamnitih stebrov je namreč začela potekati vzdolž skoraj vodoravnih lezik in večinoma subvertikalnih prelomov in razpok že pod debelimi plastmi naplavin in prsti. Kamniti stebri v gozdu so posamezni ali gručasti. Prevladujoča in najbolj značilna oblika stebrov je gobasta, saj se v njej v navpični smeri odražajo spreminjajoče se litološke lastnosti karbonatnih plasti. ključne besede: lunanski kamniti gozdovi, litologija, skalni relief, morfogeneza, JZ Kitajska. INTRODUCTION Shilin-stone forests (Knez & Slabe in print) developed from subcutaneous karst karren where thick layers of sediments and soil covered the carbonate rock. Tey are composed of stone pillars and stone teeth (Song 1986), formed on various horizontal and mildly inclined rock beds (5–150), cut by vertical faults and cracks (ford & Salomon & Williams 1996). Te central part of the Lunan stone forest covers over 80 ha, while larger and smaller stone forests spread over 350 km2. Unique among the stone forests is Lao Hei Gin. Te forest is composed of pillars, standing in groups or individually, that can reach up to 20 m in height. Most are lower, however, up to about 10 m. Te dominant and most characteristic form of the pillars is a mushroom-like shape. Watercourses run through caves that occur some 20 to 30 m deep below the forests. We have presented our research of the Lunan stone forests in more detail in descriptions and collected notes published in the book “South China Karst 1” (Chen et al. 1998) and elsewhere (e.g. Knez & Slabe 2001a, 2001b, 1 Karst Research Institute, ZRC SAZU, Titov trg 2, SI-6230 Postojna, Slovenia, e-mail: knez@zrc-sazu.si, slabe@zrc-sazu.si Received / Prejeto: 29.06.2006 ACTA CARSOLOGICA 35/1, 99–105, LJUBLJANA 2006 MARTIN KNEZ & TADEJ SLABE 2002). In this article we are adding the results of our ex-ploration of yet another stone forest, unique in its forma-tion. Figure 1: lao hei gin stone forest. Slika 1: lao hei gin kamniti gozd. LITHOLOGICAL Te geological column is divided into 5 lithologically and morphologically diverse sequences: A, B, C, D and E (figs. 3, 4, 5). Sequence A is built mostly of low-porous and grained late diagenetic dolomite, sequence B is of highly porous late diagenetic grained dolomite, sequence C is of slightly dolomitic limestone, sequence D is of low-porous grained late diagenetic dolomite and sequence E is of compact speckled dolomitic limestone. Te total thickness of the researched geological profle (stone pil-lar) is 26 m. SEQUENCE A Tis sequence is 7 m thick. Te lower part of the stone pillar is formed from highly re-crystalised dolosparite to dolomicrosparite of a grainstone type. Te primary limestone had been highly diagenetically transformed - un-der a microscope we can observe subhedral to euhedral dolomite grains, which form a hipidiotopic to idiotopic structure. Te dolomite grains are up to one-third of a Te Lao Hei Gin stone forest (figs. 1, 2, 3) lies 20 km north of Major Stone forest. Individual stone pillars and larger rock blocks shaped by corrosion and erosion cover only about 2 km2. Morphologically the stone pillars are similar to those in the Naigu stone forest. Figure 2: lao hei gin stone forest. top view. Slika 2: lao hei gin kamniti gozd. Pogled z vrha. Figure 3; Cross section of the lao hei gin stone forest. Slika 3: Prerez lao hei gin kamnitega gozda. TICS Of THE STONE fOREST millimetre in size. In difused light they mostly have a slightly brown hue, whereas individual larger grains are exceptionally clean and almost totally translucent. Autog-enous overgrowth is clearly visible in a small percentage of the dolomite crystals. Te rock also contains a certain percentage of calcite. Secondary porosity is substantial. SEQUENCE B Sequence B is 8 m thick and does not mineralogically dif-fer much from sequence A; on average, however, the rock does contain twice the amount of calcite as the rock from sequence A. Te rock in this sequence is a grainstone-type dolosparite to dolomicrosparite. Grainstone-type dolomite (dolomicrosparite to dolosparite) consists of subhedral to euhedral dolomite grains that form a hipidiotopic to idiotopic structure. Te essential diference of the rock from both sequences is that the rock in se-quence B shows substantially more secondary porosity than the rock in sequence A. On average, the dolomite 100 ACTA CARSOLOGICA 35/1 – 2006 LITHOLOGICAL AND MORPHOLOGICAL CHARACTERISTICS AND ROCK RELIEf Of THE LAO HEI GIN STONE fOREST Figure 4: Single mushroom-like stone pillars. Slika 4: Posamezni kamniti stebri gobastih oblik. Figure 5: Stone pillar, which shape is dictated by rock. Slika 5: Steber, katerega obliko narekuje kamnina. crystals are smaller than the crystals in sequence A - in the upper part of the sequence even less than one tenth of a mm - and less pure. SEQUENCE C S equence C is 4 m thick. Here the ro ck is mostly limestone with no more than 10% dolomite crystals. Te boundary between sequences B and C is sharp and immediately Figure 6: Subcutaneously shaped stone teeth. Slika 6: Podtalno oblikovani kamniti zobje. transforms into biopelintramicrite to biopelmicrosparite in the vertical direction. Te fossil remains are generally less preserved; only occasionally did some foraminif-eras and thick-shelled gastropods have better undergone the diagenetic processes. Secondary porosity is barely present. SEQUENCE D Te thickness of sequence C is 5 m. Te upper part of the pillars forms a highly re-crystalised and grained do-losparite to dolomicrosparite. Te boundary between se-quence C and sequence D is ofen blurred and difcult to determine visually and macroscopically. Te primary limestone was highly diagenetically altered. Under a mi-croscope we can observe subhedral to euhedral dolomite grains, which form a hipidiotopic to idiotopic structure of the rock Te dolomite grains in this sequence are also about one-third of a mm in size. In difused light the dolomite grains mostly have a slightly brown hue. SEQUENCE E Sequence E is up to 2 m thick. Massive dolomitic limestone is characteristic for the upper part, which we found only on some pillars. On the outside it has a coarse and speckled appearance, characteristic of a large part of the Naigu stone forest (Knez & Slabe 2001a). Because of the bulginess on the rock surface, coarseness and subsequent algae overgrowth, the dolomite felds are dark grey On the rock surface we can see them as dark grey to black spots, which gradate into lighter limestone felds in all directions. In most parts of the sequence, the percentages of the surface, as well as volume, of non-dolomitic limestone and dolomitic zones are equal. ACTA CARSOLOGICA 35/1 – 2006 101 MARTIN KNEZ & TADEJ SLABE SHAPE Of THE STONE fOREST Te larger groups of stone pillars consist of several tens of pillars (figs. 1, 2, 3, 4). Between them are corroded fssures or narrow passages. Te smaller groups of pillars, composed of ten or fewer pillars, are most ofen cut only by cracks and corroded fssures. Over a relatively large area of the stone forest we fnd only individual pillars and stone teeth. Individual pillars are relatively large, broad and high, or else they are low and wide. Te bedding is refected in the form of pillars mainly because of the diverse composition of the rock. Below the soil, as well as on the surface, the B beds decay and de- compose faster, and subsequently the individual thinner and tall pillars are unstable. Te tall pillars are generally mushroom-shaped. Te beds of sequences A, C and D are more resistant and extensive. In some areas the upper parts of the pillars have disappeared, and only low pillars formed in rock sequence A are preserved. Subcutaneous tubes transformed by rainfall dripping down the pillars frequently hollow the porous rock of the beds B. Te rare pillar tops that form in such rock are ofen diversely shaped. THE ROCK RELIEf Of THE STONE fOREST We fnd three distinct types of rock forms on the pillars: subcutaneous forms, forms created by rainfall and com-bined rock forms. Te creation of these rock forms and their uniqueness is defned mainly by the rock itself, es-pecially where it is exposed. Te subcutaneous forms are less explicitly defned by the rock SUBCUTANEOUS ROCK fORMS Tese forms are divided into those that were formed be-low the deposits and the soil as the result of water fowing at the contact of the rock and the soil, and forms created by water percolation through the soil that only partially covers the rock, and the rock forms that formed at the level of the soil or deposits that surround the rock (Slabe 1999). Te frst group of subcutaneous rock forms are subcutaneous channels of various sizes that were formed by continuous water-fow at the contact of the rock and the deposits that covered the rock and flled the fssures in the vertical cracks. Te diameter of the larger channels can reach up to several metres (fig. 6). Tey dissect all diferent rock sequences. At the tops of the higher pillars they were transformed by rainfall, while the B beds decompose too quickly for the channels to remain preserved on them for a longer period. Tey are therefore mainly a characteristic of the lower parts of the pillars and stone teeth. Subcutaneous scallops that form on the relatively permeable contact area of the rock and the deposits are preserved mostly in beds A, C and D or on the B beds that had been exposed for only a shorter period. Also the walls of the largest subcutaneous channels could be dissected by them. Te more extensive pillar tops and teeth are seg-mented by mid-sized and smaller subcutaneous chan- 102 ACTA CARSOLOGICA 35/1 - 2006 nels and subcutaneous cups (Slabe 1999, 259) that were formed under the soil that partially covered the rock, therefore as the result of water percolation through the soil and its fow along the area where it touches the rock Tey have characteristic semi-circular cross sec-tions or cross sections in the shape of the upturned let-ter omega. Tey are wider at the lower part of cross-section, their diameters can reach up to 1 m. Tey are usually linked into a branched network. Te subcutaneous cups (Slabe 1999, 263) are of various sizes and diameters, from a few centimetres to a metre or more. Tey occur on the tops of large pillars and on the bot-toms of funnelled notches in the walls below them. Te most porous strata are fairly densely perforated by subcutaneous tubes of diameters ranging between a few centimetres and a metre or two. Te pillars in the B beds are generally distinctly un-dercut below the ground, which is visible from the over-hanging lower parts of the pillars that have developed on these rock strata. COMBINED ROCK fORMS Tese are the larger channels in the upper parts of the pillar walls. Tey develop as the result of water fowing from subcutaneous channels, which appear on the larger pillar tops, or by water dripping from the funnelled notches. Subcutaneous cups occur at the bottom of the latter or else were once present there. Tey thus have larger or smaller funnel-shaped outlets at the edges of the tops, which have in most cases been transformed by rainfall. Tey are especially noticeable in the beds of the A, C and D groups, or, if the top is in the D beds they reach to the B beds. Teir distribution and shapes, relatively narrow and deep, are defned by how crushed the rock is, how LITHOLOGICAL AND MORPHOLOGICAL CHARACTERISTICS AND ROCK RELIEf Of THE LAO HEI GIN STONE fOREST serrated the rims of the rock are, and also by the compo-sition of the rock. Rainfall transforms, mainly deepens, the former subcutaneous channels and cups that criss-cross the wider tops. Such rock formations therefore exhibit traces of subcutaneous dissolution of the rock and of the rain-water, which can gradually, with the denudation of the rock, completely take over. Below the soil the channels and cups are relatively evenly shaped with smooth walls, but as they become exposed their shapes become distinc-tively uneven with many branches and segmented rims. Half-bells are formed on the more durable levels of soil and deposits that surround the pillars (Slabe 1999). ROCK fORMATIONS CARVED By RAINfALL Tese types of rock formations, especially the smallest futes and cups, do not occur on this type of rock Te ex-ceptions are the more limited highest zones of the stone forest, where the tooth tops are created in the dolomitic limestone of the E beds. Segmentation of most of the tops is therefore defned by the composition and diversifca-tion of the rock (fig. 7). Rock exposed to rainfall is coarse and contains only rock formations that do not exceed the size of the individual segmentation of the coarse surface. Te solution pans with distinctly segmented and coarse surfaces are developing from subcutaneous cups; only the bottoms of solution pans that are covered by thin layer deposits and are overgrown remain even and relatively smooth. On the steep walls the segments resemble channels, usually very narrow but relatively deep and angulated, with diameters that measure 1-10 cm and are 2-3 m long. At the highest section of the stone forest we fnd dolomitic limestone on the pillar tops, with futes carved in them (fig. 8). Smaller channels of a diameter of 1-2 cm Figure 8: Dolomitic-limestone stone teeth. Slika 8: Dolomitno apnenčasti kamniti zobje. appear on the limestone where there are felds of dolomite in the limestone, which generally protrude a centimetre or two from the wall and do not exhibit other rock formations. Figure 7: Te top of stone pillar carved by rainfall. Slika 7: vrh kamnitega stebra oblikovan z deževnico. CONCLUSION Te stone pillars in the forest are either solitary or in groups within which there are only cracks and fssures. Tey were formed at various levels on nearly horizontal rock beds and in corresponding shapes. Te exposed lower part of the geological profle or stone pillar is com-posed of fully dolomitised limestone, the middle part (sequence B) is composed of porous dolomite and the upper parts of the stone pillars are composed of more durable limestone and dolomitic limestone, resistant to erosion. Sequence B rock beds decay and decompose faster, below, as well as above the ground, and since they are generally covered by more durable strata, the pillars form characteristic mushroom-like shapes. Te pillars are wider below the narrower parts if the lower dolomite strata are exposed. Te rock relief consists of various groups of rock forms: subcutaneous, those carved by rainfall and com-bined forms - their characteristics are defned by the composition of the various rock beds. Te tops are sharp and well segmented around the cracks. Such are all the ACTA CARSOLOGICA 35/1 - 2006 103 MARTIN KNEZ & TADEJ SLABE forms carved by rainfall - these are channeled rock forms and solution pans. Teir surface is notably coarse. On limestone beds that occur only in some of the highest ly-ing parts of the stone forest, the futes and small channels are evenly shaped. On porous and faster-disintegrating beds, there are no distinct rock formations carved by rainfall, except at the beginning on exposed rock covered by more rounded parts of the subcutaneous rock relief. Chen xiaoping, Gabrovšek, f., Huang Chuxing, Jin yu-zhang, Knez, M., Kogovšek, J., Liu Hong, Petrič, M., Mihevc, A., Otoničar, B., Shi Mengxiong, Slabe, T., Šebela S., Wu Wenqing, Zhang Shouyue & Zupan Hajna, N., 1998: South China Karst I.- Založba ZRC, 19, 247 pp., Ljubljana. ford, D., Salomon, J.N. & Williams P. , 1996: Les »forets de Pierre« ou »Stone forests« de Lunan.- Karstologia 28/2, 25-40. Knez, M., 1998: Lithologic Properties of the Tree Lunan Stone forests (Shilin, Naigu and Lao Hei Gin).- In: Chen xiaoping et al., South China Karst I, Založba ZRC, 19, 30-43, Ljubljana. Knez, M. & Slabe, T., 2001a: Oblika in skalni relief stebrov v Naigu kamnitem gozdu (JZ Kitajska).- Acta carsologica 30/1, 13-24, Ljubljana. Knez, M. & Slabe, T., 2001b: Te Lithology, Shape and Rock Relief of the Pillars in the Pu Chao Chun Stone forest (Lunan Stone forests, NW China).- Acta car-sologica 30/2, 129-139, Ljubljana. Tese are distinctly formed on all diferent types of rock beds. Only their surface is mildly coarse. In our research we have observed (Knez 1998; Slabe 1998; Knez & Slabe 2001a, 2001b) that the lithological composition and tectonic properties of the rock play a decisive role that corresponds to the morphological pic-ture of the stone pillars and that are essentially important in selective corrosion and erosion. Knez, M. & Slabe, T., 2002: Lithologic and morphologi-cal properties and rock relief of the Lunan stone forests. In: Gabrovšek, f. (ed.), Evolution of karst: from Prekarst to Cessation.- Založba ZRC, 259-266, Ljubljana. Knez, M. & Slabe, T., in print: Shilin - Te formation of Stone forests on Various Rock (Lunan, yunnan, China).- Acta geologica sinica (Engl. ed.), Beijing. Slabe, T., 1998: Rock relief of pillars in the Lunan stone forest.- In: Chen xiaoping et al., South China Karst I, Založba ZRC, 19, 51-67, Ljubljana. Slabe, T., 1999: Subcutaneous rock forms. Acta carsologi-ca 28/2, 255-271, Ljubljana. Song, Lin Hua, 1986: Origination of stone forest in Chi-na.- International Journal of Speleology 15 (1-4), 3-13. REfERENCES 104 ACTA CARSOLOGICA 35/1 – 2006 LITHOLOGICAL AND MORPHOLOGICAL CHARACTERISTICS AND ROCK RELIEf Of THE LAO HEI GIN STONE fOREST LITOLOŠKE IN MORfOLOŠKE ZNAČILNOSTI TER SKALNI RELIEf LAO HEI GIN KAMNITEGA GOZDA (LUNAN, JZ KITAJSKA) POVZETEK Lao Hei Gin kamniti gozd (Sl. 1, 2, 3, 4) je nastal iz podtal- Skladovitost kamnine se v obliki stebrov odslikava nih kraških škrapelj. Karbonatne kamnine so bile namreč predvsem zaradi različne sestave kamnine v posameznih pokrite z debelimi plastmi naplavin in s prstjo. Kamniti plasteh. Skladi B tako pod tlemi kot na površju prepereva-stebri in kamniti zobje so se razvili v raznovrstnih, skoraj jo in razpadajo hitreje in posamezni tanjši ter visoki stebri vodoravnih ali položnih skladih kamnine, ki so jo razko- so zato neobstojni. Visoki stebri pa so praviloma izrazite sali navpični prelomi in razpoke. Gozd sestavljajo stebri, gobaste oblike. Skladi A, C in D so namreč obstojnejši ki so gručasto strnjeni ali pa posamezni in dosežejo do 20 in obsežnejši. Ponekod zgornjih delov stebrov ni več, m višine, večina je nižjih, visokih do 10 m. Prevladujoča ohranjeni so le nizki stebri, ki so oblikovani v kamnini in najbolj značilna oblika stebrov je gobasta. 20 do 30 m A. Porozna kamnina skladov B je pogosto prevotljena s globoko pod gozdom so jame, skozi katere se pretakajo podtalnimi cevmi, ki jih preoblikuje deževnica, polzeča vodni tokovi. Lao Hei Gin kamniti gozd leži okrog 20 po stebrih navzdol. Redki vrhovi stebrov, ki se oblikujejo km severno od Shilina. Posamezni kamniti stebri in večji na takšni kamnini, so največkrat neenotnih oblik. korozijsko in erozijsko preoblikovani bloki kamnine za- Skalni relief sestavljajo vse značilne skupine skalnih vzemajo le okrog 2 km2. Morfološko so kamniti stebri oblik, podtalne (Sl. 6), tiste, ki jih dolbe deževnica in ses-podobni tistim iz Naigu kamnitega gozda. tavljene skalne oblike, jim pa značilnosti v precejšni meri Glede na litološke in morfološke značilnosti smo določa sestava različnih skladov kamnine. Vrhovi so os-geološki stolpec razdelili v 5 sekvenc: A, B, C, D in E (Sl. trih in ob razpokah drobno razčlenjenih oblik, takšne so 3, 5). Sekvenca A je zgrajena večinoma iz slabo poroznega vse skalne oblike, ki jih dolbe deževnica, to so žlebovom zrnatega poznodiagenetskega dolomita, sekvenca B iz podobne skalne oblike in škavnice, njihova površina pa zelo poroznega poznodiagenetskega zrnatega dolomita, je izrazito hrapava (Sl. 7). Na apnenčastih skladih, ki se sekvenca C iz rahlo dolomitnega apnenca, sekvenca D iz pojavijo le na posameznih najvišjih delih kamnitega goz-slabo poroznega zrnatega poznodiagenetskega dolomita, da, so žlebiči in žlebovi pravilnih oblik. Na poroznih in sekvenca E iz kompaktnega marogasto dolomitiziranega hitreje razpadajočih skladih ni značilnih skalnih oblik, ki apnenca. Skupna debelina raziskanega geološkega profla jih dolbe deževnica, le sprva, po razgaljenju kamnine, jih (kamnitega stebra) je 26 m. prekrivajo zaobljene oblike podtalnega skalnega reliefa. Večje gruče kamnitih stebrov so sestavljene iz več Te se namreč izrazito oblikujejo na vseh različnih skladih deset stebrov. Med njimi so špranje ali pa ožji prehodi. kamnine. Le njihova površina je drobno hrapava. Manjše gruče stebrov, ki jih sestavlja deset in manj stebrov, Pri naših raziskavah vse bolj ugotavljamo (Knez pa sekajo največkrat le razpoke in špranje. Na razmeroma 1988; Slabe 1988; Knez & Slabe 2001a, 2001b), da se tudi veliki površini kamnitega gozda so le posamezni stebri najmanjše litološke razlike v kamnini zelo jasno odražajo in skalni zobje. Posamezni stebri so razmeroma veliki, v morfogenetskem razvoju kamnitih gozdov. široki in visoki ali pa so nizki (1-2 m) in široki. ACTA CARSOLOGICA 35/1 – 2006 105