Middle and Late Permian Reefs—Distributional Patterns and Reservoir Potential
Published:January 01, 2002
Middle and Late Permian reefs flourished for about 20 million years in the Tethys, the Panthalassan ocean, the Delaware Basin, the Zechstein Basin, and the Northwest Pangean era tonic basin Eight reef types, which were differentiated on the basis of their taxonomic composition, belong to four significantly different reef environmental settings: (1) The Tethyan carbonate factory has the highest taxonomic diversity of macro-reefbuilders, yields massive, probably zooxanthellate rugose corals, and is mud-rich. Reef domains occur along the southwestern shelf margin and on Cimmerian as well as Cathyasian terranes. Typical representatives are sponge reefs found in Tunisia or Oman and coral reefs described from China. (2) Epeiric reefs are dominated by micro-framework (e.g., microbial precipitates and low-grawing metazoans), largeamounts of synsedimentary, marine-phreatic cements, and few macro-reefbuilders. Classic localities are known from the Delaware and the Zechstein basins. (3) Reefs of some Panthalassan oceanic buildups (e.g., Mino terrane, Japan) are composed of caleimicrobes, low-growing metazoans, and large amounts of sediment, but macro-reefbuilders (large coralline sponges and massive rugose corals) are absent. (4) Cool-water reefs differ significantly from their tropical counterparts by depositional geometries and taphonomic history. The ethinoderm-and bryozoan-rich associations, which lack cosmopolitan Archaeolilhoporella hidensis, accumulated in biostromes on slightly dipping ramps and did not develop structures with significant relief. The faunas are reworked due to moderate synsedimentary cementation and high turbulence and are well known from the Northwest Pangean cratonic basin.
Important Permian reefbuilders are microbes, Archacolithoporclla, Shamovella (formerly Tubiphytes), coralline sponges, rugose corals, calcareous algae, bryozoans, and brachiopods. Algal-cement reefs with various percentages of microbial precipitates are a common reef type, lacking only in the high latitudes, and have a cosmopolitan character; Shamovella, Archaeolithaparelta, and sponges are common and widespread reefbuilders.
Permian reef evolution is discontinuous and characterized by pulses of growth as well as the final demise of late Paleozoic communities followed by the severe gap without true metazoan reefs during the Scythian, The end-Permian mass extinction is twofold, comprising a pre-Lopingian and a Changhsingian event. The latest Permian reefs are restricted to the equator and are characterized by high diversities Intercalated sediments enriched in calcareous algae indicate global warming.
Middle and Late Permian reefs bear an underestimated hydrocarbon reservoir potential, especially in (1) epeiric basins with occasional upwelling of hypersaline waters, (2) karatified and dolomitized Tethyan reefs, (3) carbonates related to upwelling at continental margins, and (4) cool-water carbonates with reefbuilders. Productive reservoirs are known from Tethyan reefs, including China, Thailand, and Tunisia.
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Phanerozoic Reef Patterns
Detecting patterns and processes of ecosystem evolution is among the main challenges of an integrated earth system science in the 21st century. The evolution of reefs reflects changes triggered by evolutionary innovations and variations in global and regional controls at different scales. The prime fossil record of Phanerozoic reefs offers the opportunity to trace these patterns through space and time. Phanerozoic Reef Patterns presents a comprehensive and up-to-date review on the history of reef building in the last 540 million years. A selection of internationally respected reef specialists presents a database on ancient reefs that is hardly available for any other ecosystem. The thoroughly documented patterns are analyzed with respect to global change, whose impact on living reefs is intensely discussed today. Phanerozoic Reef Patterns stands out from recent reviews on reef evolution by its careful qualitative and quantitative approach based on a comprehensive and multifaceted databank, by the strong focus on data, by a complete and unified coverage of the Phanerozoic from the Early Cambrian to the late Neogene, by emphasizing paleogeographic reef distributions presented on 32 newly developed color maps, and by a detailed index that makes the book a valuable research tool.