Phenomena of lithification

Phenomena of lithification and cement precipitation within carbonate-litihic rockslides.

‘Limpid cement’ herein designates any type of carbonate cement that is more-or-less pure and translucent in thin section. ‘Limpid cement’ as used below may include blocky calcite spar, prismatic calcite, and fibrous aragonite. All types of limpid cements of calcium carbonate in principle are well-suited for U/Th dating.

Phenomenon

Description

Remarks

     

Underboulder breccias

Pockets and crusts up to a few dm thick of cemented breccias adherent on and formed along the underside of boulders

Common. Often contains interstitial limpid cements. Such cements can be good proxies for rockslide event age

     

Breccia crust

Crust a few dm to more than 1 m thick of rockslide material cemented into breccia.

 

Crust is not associated with indiviudal boulders, but is concordant with the local surface of the rockslide mass

Observed in the Tamins rockslide only.

 

Contains limpid cements that may provide a good proxy age of rockslide event

     

Podiform to stratiform bodies of breccia

Irregular to stratiform bodies wherein the rockslide material is lithified into breccia by cements (limpid cements, micritic cements)

Observed for inner parts of Flims rockslide only (Rabiusa gorge)

 

Limpid cements probably suited for U/Th dating, but significance of age uncertain

     

Stalactites, flowstone ridges

Small stalactites and ridges of flowstones on undersides of boulders

 

Stalactites and flowstone ridges commonly consist of limpid calcite cement

Common in Tschirgant rockslide.

 

Should yield precise U/Th ages that may be good proxies of event age

     

Micritic crusts

Crusts on flanks and undersides of boulders, or on flanks and overhangs of coherent but non-lithified rockslide material

 

Crust are up to a few mm thick of (a) homogeneous micrite, (b) micrite with wrinkly to mammillary to digitate lamination

Common. Probably of low or no use in U/Th age determination