Multiphase formation of Weichselian cryogenic calcites, Riesenberg Cave (Suntel/NW Germany)

作者：Richter Detlev K; Meyer Stefan; Scholz Denis; Immenhauser Adrian^*

来源：Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften, 2013, 164(2): 353-367.

DOI：10.1127/1860-1804/2013/0016

• speleothem
• petrography
• Weichselian
• carbon and oxygen isotopes
• permafrost

For the first time, we here report cryogenic calcites from the Riesenberg Cave in NW Germany. The cave formed in the Korallenoolith Formation, a shallow marine carbonate facies of Late Jurassic age. Cryogenic calcites from the Riesenberg Cave are present as mono- as well as polycrystalline particles and have diameters of commonly less than 10 mm. Oxygen isotope values of cryocalcites range from 0 to -16.5 parts per thousand. Four main types and three subtypes of cryocalcites are present. Main types include: (i) Braided sinter, (ii) rhombohedral fabrics, (iii) spherulites and (iv) skeletal crystal sinters. Subtypes include: (i) rhombohedron skeletal crystal sinters, (ii) fungiform sinters and (iii) sinters with voids. The formation of these calcites was most likely related to precipitation of slowly freezing cave pools resulting from high-frequency freezing-thawing cycles at the transition between glacial (stadial) and interglacial (interstadial) conditions during permafrost melting phases. Th-230/U dating suggests Weichselian ages of 11.9-12.0, 53.7, 61.6-62.0 and 66.4 ka. These data suggest four main formation periods. Cryocalcites remained on the cave floor after the melting of the cave ice bodies. The genesis of cryocalcites in a cave overlain by 35 to 37 m of host rock provides novel insights on the minimum depth of permafrost penetration during the younger Dryas (12.7-11.7 ka BP).

• 出版日期2013-6