Solution‐collapse breccias of the Minkinfjellet and Wordiekammen Formations, Central Spitsbergen, Svalbard: a large gypsum palaeokarst system

• Published in: Sedimentology
• Main Authors: ELIASSEN, ARILD, TALBOT, MICHAEL R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2005
• Subjects: Billefjorden; Svalbard; Spitsbergen
• Online Access: http://dx.doi.org/10.1111/j.1365-3091.2005.00731.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-3091.2005.00731.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3091.2005.00731.x

Abstract Large volumes of carbonate breccia occur in the late syn‐rift and early post‐rift deposits of the Billefjorden Trough, Central Spitsbergen. Breccias are developed throughout the Moscovian Minkinfjellet Formation and in basal parts of the Kazimovian Wordiekammen Formation. Breccias can be divided into two categories: (i) thick, cross‐cutting breccia‐bodies up to 200 m thick that are associated with breccia pipes and large V‐structures, and (ii) horizontal stratabound breccia beds interbedded with undeformed carbonate and siliciclastic rocks. The thick breccias occur in the central part of the basin, whereas the stratabound breccia beds have a much wider areal extent towards the basin margins. The breccias were formed by gravitational collapse into cavities formed by dissolution of gypsum and anhydrite beds in the Minkinfjellet Formation. Several dissolution fronts have been discovered, demonstrating the genetic relationship between dissolution of gypsum and brecciation. Textures and structures typical of collapse breccias such as inverse grading, a sharp flat base, breccia pipes (collapse dolines) and V‐structures (cave roof collapse) are also observed. The breccias are cemented by calcite cements of pre‐compaction, shallow burial origin. Primary fluid inclusions in the calcite are dominantly single phase containing fresh water (final melting points are ca 0 °C), suggesting that breccia diagenesis occurred in meteoric waters. Cathodoluminescence (CL) zoning of the cements shows a consistent pattern of three cement stages, but the abundance of each stage varies stratigraphically and laterally. δ 18 O values of breccia cements are more negative relative to marine limestones and meteoric cements developed in unbrecciated Minkinfjellet limestones. There is a clear relationship between δ 18 O values and the abundance of the different cement generations detected by CL. Paragenetically, later cements have lower δ 18 O values recording increased temperatures during their precipitation. Carbon isotope values of ...