Sthreepura cave at Kiriwanagama, south central Sri Lanka: A network cave in saprolite and proterozoic quartzite

Sthreepura Cave at Kiriwanagama consists of an upper level of cavities in quartzite formed by arenization and a lower level developed in a saprolite formed from the weathering of gneiss sandwiched between two layers of quartzite. The lower level cave is not like most arenization and phantom rock caves as the walls are composed of saprolite, not exhumed unweathered rock. The cave is not a soil pipe as it is not in soil, lacks the characteristic features of soil pipes and has formed directly below, not above an aquiclude. Sthreepura Cave at Kiriwanagama is a network cave in saprolite. Speleogenesis in the lower level began with the development of joint-guided tubes in the saprolite directly below the upper layer of quartzite, probably under phreatic conditions. Later erosion under vadose conditions removed the saprolite to produce a network of passages with a rectangular profile. Widening of the passages ultimately caused ceiling failure producing breakdown chambers, but fallen slabs of quartzite armoured the walls of the Main Passage of the cave protecting them from undercutting.Key words: Sri Lanka, gneiss, network cave, saprolite, arenization.Jama Sthreepura pri Kiriwanagami, južni del osrednje Šri Lanke: Mreža rovov v saprolitu in proterozojskem kvarcituJamo St hreepura pri Kiriwanagami sestavljata gornji nivo arenizacijskih votlin v kvarcitu ter spodnji nivo v saprolitu, ki je nastal s preperevanjem gnajsa med plastmi kvarcita. Tudi stene rovov spodnjega nivoja so iz saprolita, kar kaže na drugačen razvoj od znanih arenizacijskih in fantomskih jam. Jama nima lastnosti preperinskih cevi in je v nasprotju s temi nastala neposredno pod (in ne nad) akvikludom. Jama Sthreepura pri Kiriwanagami predstavlja mrežo kanalov nastalih v saprofitu.. Speleogeneza se je začela z razvojem cevi vzdolž razpok v saprolitu, neposredno pod gornjo plastjo kvarcita, verjetno v freatičnih pogojih. Kasnejša erozija v vadozni coni je saprolit odstranila in tako ustvarila mrežo rovov pravokotnega profila. Širjenje rovov je privedlo do rušenja stropa in nastanka podornih dvoran. V glavnem rovu so padli bloki kvarcita zaščitili stene in preprečili nadaljnje spodkopavanje v glavnem rovu jame.Ključne beside: Šri Lanka, gnajs, mreža rovov, saprolit, arenizacija

Caves and karst-like features in Proterozoic gneiss and Cambrian granite, southern and central Sri Lanka: An introduction

There has been little study of the geology and geomorphologyof the caves and karst-like features developed in the Proterozoicgneiss and Cambrian granite of Sri Lanka. This lack of studyis surprising given that caves and rockshelters in these rockscontain significant archaeological and cultural sites. Caves andkarren, both mimicking those developed in carbonate rocks,have formed both in gneiss, which is the dominant rock type ofthe Proterozoic crust of the island and in granite. In addition tooverhangs, boulder caves, soil pipes and tectonic caves, tunnelcaves, arch caves and block breakdown caves of significant sizeare developed in siliceous rocks in Sri Lanka. While metamorphoseddolomites are interfoliated within the gneissic suite,simple removal of carbonate by solution from within the surroundingrock cannot account for all or most of the speleogenesisobserved. While spalling and breakdown are responsiblefor cave enlargement cave initiation is probably due to eitherphreatic solution of silicates and/or phantom rock processes.Speleothems and cave minerals including silicates, phosphates,gypsum, carbonates and niter are found in the caves. Activesilicate speleothems are not restricted to joints and fissures andsuggest that solution of silicates is currently occurring withinthe body of the rock in the vadose zone. While guano is thelikely source of the phosphate, sulfate and nitrate, the sourceof the calcium in the carbonates remains unclear. Caves in theintrusive and metamorphic rocks of Sri Lanka are enigmatic.They are unexpectedly similar in appearance to their carbonatekarst counterparts. Continuing research will allow them tohold a mirror to our understanding of speleogenesis, mineralizationand sedimentation in carbonate karst caves

Microbiological study in a gneissic cave from Sri Lanka, with special focus on potential antimicrobial activities

The emergence of antibiotic resistance is a global health crisis, thus the search for novel antimicrobial compounds has become a continuous necessity. Underexplored and extreme environments, such as cave ecosystems, have been identified as a promising potential source for the discovery of novel microorganisms with novel antimicrobial compounds (AMC). This study presents the first cave microbiological investigation in Sri Lanka, with a special preference for bioprospecting of novel AMC. The cave sediment characterization demonstrated the presence of close to strong acidic conditions (pH 3.1 – 3.3) and thus indicates the possibility of isolating acidophilic microorganisms. Eight cave wall/ceiling fungal strains were isolated from Sthreepura Cave - Kuruwita and identified using both morphological and ribosomal Internal Transcribed Spacer (ITS) region sequence analysis. Interestingly, four fungal isolates (Penicillium panissanguineum, P. cremeogriseum, Aspergillus bertholletius and Trichoderma yunnanense) were found to be the first records in Sri Lanka. Of these eight isolates, three showed antimicrobial activity (AMAs) against at least one of the five tested human pathogens in preliminary screening, while A. fumigatus (SKW 404) strain showed the highest AMA against Staphylococcus aureus (ATCC 11778) assessed by agar culture plug method on Muller Hinton Agar (MHA). Crude Ethyl Acetate (EtOAc) fraction of both mycelial and Potato Dextrose Broth (PDB) extracts of A. fumigatus demonstrated similar bioactive metabolic profiles with four corresponding chemical fractions [Rf = 0.47, 0.56, 0.65, 0.82; EtOAc: Hexane (4:1, v/v)] in TLC: agar overlay bioassay. The present study indicates that there is potential for discovering novel Sri Lankan deep cave microorganisms and bioprospecting of their novel bioactive compounds. Hence, further island-wide in-depth cave microbiological investigations are required for a better understanding of the Sri Lankan cave microbiology