Deepwater Sedimentary Structures - Mud Volcanoes.
This is the fourth gallery of sedimentary structures of deepwater systems and includes outcrops of the Paleozoic rocks of the Appalachian Mountains, the Upper Carboniferous of the Shannon basin in Co Clare in Ireland and a number of other localities around the world.
This section focuses on sedimentary structures found within and on submarine fans, the channels that feed them and the adjacent basin. These include dewatering of sediment weighted down by the arrival of a downslope transport event, forming submarine volcanoes. Also included are some ichnofossil structures.
Submarine sediment volcanoes are found in the Ross and Gull formations of Co. Clare. These small volcano-shaped cones, often less than 1-2 m tall, are built of mixtures of mud, clay and/or sand. These structures were probably generated from a mixture of water and fine sediment that escaped from a vent ion the sea floor like a fluid lava flow; or were ejected into the water as a lava fountain by an escaping slurry of water and sediment. In the case of the Ross formation the sediment was generated by the dewatering mud diapers. Other similar features elsewhere in other geological settings are generated by escaping methane from the melting of clathrate hydrate deposits; and/or volcanic gas and boiling water. Thus it is contended that the fine sediments of mud volcanoes come from either a piercement structure created by a dewatering pressurized mud diapir that breached the sediment/air or seafloor surface; from clathrate hydrate deposits whose temperatures were elevated above the freezing point and were potentially associated with the ejected materials; and/or volcanic gases and heat escaping from a buried magma. Spectacular examples can be seen in Azerbaijan where eruptions are driven from mud reservoirs containing melting clathrate hydrate deposits. Here seeps have temperatures up to 2–3 °C above the ambient temperature, unless they catch fire or explode?
Unless otherwise stated many of the photographs below are from Christopher Kendall and Peter Haughton. A number of the images have been grabbed from the web, placed there by generous geologists and utilized with acknowledgement to them where data is available on the photographer. If we missed acknowledgement to you or you have something better you would prefer placed here, please let us know.
Tuesday, September 17, 2013