Petrographic recognition of layer-bounding surfaces in stalagmites offers an important tool in constructing paleoclimate records. Previous petrographic efforts have examined thickness of layers (a possible proxy for annual rainfall) and alternation of layers in couplets (a possible indicator of seasonality). Layer-bounding surfaces, in contrast, delimit series of layers and represent periods of non-deposition, either because of exceptionally wet or exceptionally dry conditions.

Two types of layer-bounding surfaces can be recognized according to explicitly defined petrographic criteria. Type E layer-bounding surfaces are surfaces at which layers have been truncated or eroded at the crest of a stalagmite. Keys to their recognition include irregular termination of layers otherwise present on the stalagmite’s flank, dissolutional cavities, and coatings of non-carbonate detrital materials. Type E surfaces are interpreted to represent wet periods during which drip water became so undersaturated as to dissolve pre-existing stalagmite layers, and thus they necessarily represent hiatuses in the stalagmite record. Type L layer-bounding surfaces are surfaces below which layers become thinner upward and/or layers have lesser lateral extent upward, so that the stalagmite’s layer-specific width decreases. They are thus surfaces of lessened deposition and are interpreted to represent drier conditions in which drip rate slowed so much that little deposition occurred. A Type L surface may, but does not necessarily, represent a hiatus in deposition. However, radiometric age data show that Type L surfaces commonly represent significant hiatuses.

These surfaces are significant to paleoclimate research both for their implications regarding climate change (exceptionally wet or dry conditions) and in construction of chronologies in which other data, such as stable isotope ratios, are placed. With regard to climate change, recognition of these surfaces provides paleoclimatological information that can complement or even substitute for geochemical proxies. With regard to chronologies, recognition of layer- bounding surfaces allows correct placement of hiatuses in chronologies and thus correct placement of geochemical data in time series. Attention to changing thickness of annual layers and thus to accumulation rate can also refine a chronology. A chronology constructed with attention to layer-bounding surfaces and to changing layer thickness is much more accurate than a chronology in which hiatuses are not recognized at such surfaces.

There are two significant karst regions in northern Sarawak (Malaysia): Niah and Mulu. Both are famous worldwide for their well developed caves. Here we document the presence of over twenty unusual stalagmites in six cave entrances in these two regions. One of the stalagmites has been previously described as a crayback stalagmite (Lundberg and McFarlane 2011) and they all show indications of biological influence. Our study aimed to establish the locations within the cave entrances where these stalagmites are present and to provide a preliminary overview of the stalagmite forms. The environment, and especially availability and direction of light, was also studied at several sites. Surface scrapings were examined for the presence of cyanobacteria. The morphology of the unusual stalagmites is variable and includes forms that are elongated and craybacklike and others that show features not previously described in craybacks: flat tops, bulbous protuberances, phototropic rims, irregular grooves and ridges and oriented coralloid growth. Several of these features are not found in abiotic stalagmites and suggest biological control. The findings of light surveys confirm that certain features of the stalagmites are phototropically controlled. Filamentous cyanobacteria with calcified sheaths and coccoid cyanobacteria are present. we propose that this diverse group of stalagmite be named “tufaceous stalagmite” of which craybacks are thought to be a sub­group.

Speleothems are usually composed of thin layers of calcite (or aragonite). However,
cemented detrital materials interlayered between laminae of speleothemic carbonate have been also observed in many caves. Flowstones comprising discontinuous carbonate layers form due to flowing water films,while flood events introduce fluviokarstic sediments in caves that, on occasion,are recorded as clayey layers inside flowstones and stalagmites. This record provides a potential means of understand­ing the frequency of palaeofloods using cave records.In this work,we investigate the origin of this type of detritaldeposit in El Soplao Cave (Northern Spain). The age of the lowest aragonite layer
of a flowstone reveals that the earliest flood period occurred before 500 ka, though most of the flowstone formed between 422 +69/-43 ka and 400 +66/-42 ka. This suggests that the cave was periodically affected by palaeoflood events that introduced detrital sediments from the surface as a result of occasional extreme rainfall events,especially at around 400 ka.The mineralogical data enable an evolutionary modelfor this flowstone to be generated based on the alternation offload events with laminar flows and carbonate layers precipitation that can be extrapolated to other caves in which detrital sediments inside speleothems have been found. 

The aim of this study is to characterize in detail, the mineralogy of different-shaped concretions as well as to investigate the physico-chemical parameters of the associated mine drainage and drip waters in the Santa Barbara level of the Libiola Mine (NW Italy) by several geochemical and mineralogical techniques. Under the term “minothems” we are grouping all those secondary minerals that occur under certain form or shape related to the conditions under which they formed but occur in a mine, or in any artificial underground environment (i.e., "mine speleothems"). Different types of minothems (soda straw stalactites, stalactites, and draperies) were sampled and analyzed. Mineralogical results showed that all the samples of stalactites, stalagmite and draperies are characterized by poorly crystalline goethite. There are significant differences either in their texture and chemistry. Stalactites are enriched in Zn, Cd, and Co in respect to other minothems and show botryoidal textures; some of these exhibit a concentric layering marked by the alternation of botryoidal and fibrous-radiating textures; the draperies are enriched in V and show aggregates of sub-spheroidal goethite forming compact mosaic textures. Geochemical investigations show that the composition and physico-chemical parameters of mine drainage and drip waters are different from the other acidic mine water occurrences in different areas of the Libiola Mine, where minothems are less abundant. All mine water samples contain Cu, Ni, and Zn in appreciable levels, and the physico-chemical conditions are consistent with the stability of ferrihydrite, which however tends to transform into goethite upon ageing.