Contents: Contents Introduction Unconsolidated clastic sediments Sedimentary rocks Diagenesis Sediment transport and deposition Sedimentary structures Facies and depositional environments Glacial/eolian/lacustrine environments Fluvial/deltaic/coastal environments Shallow/deep marine environments Stratigraphic principles Sequence stratigraphy Sedimentary basins Models in sedimentary geology Applied sedimentary geology Reflection


Shallow/deep marine environments: Shallow/deep marine environments Shallow marine environments Shallow seas can be subdivided into clastic and carbonate-dominated systems, depending mainly on sediment supply and climatic setting Idealized models predict a general decrease of grain size with water depth (i.e., away from the shoreline); however, this simple picture is complicated by a large number of factors (e.g., shelf bathymetry)


Shallow/deep marine environments: Shallow/deep marine environments Shallow marine environments Storm-dominated clastic shelves ideally exhibit a transition from predominantly wave-rippled sands in the upper shoreface, to alternating sands and muds (tempestites with hummocky cross stratification) in the lower shoreface, to muddy facies below storm wave base Tide-dominated clastic shelves may exhibit erosional features, sand ribbons, and sand waves with decreasing flow velocities, commonly associated with mud-draped subaqueous dunes; tidal sand ridges (tens of m high, many km across) are characteristic of shelves with a high supply of sand Bioturbation can obliterate many primary sedimentary structures in shelf environments


Shallow/deep marine environments: Shallow/deep marine environments Shallow marine environments Shallow seas within the photic zone are the premier ‘carbonate factories’ Carbonate platforms can cover continental shelves or epicontinental seas, when the conditions for carbonate production (temperature, salinity, light conditions) are favorable Isolated platforms (atolls) are found in shallow seas surrounded by deep water, like extinct volcanoes


Shallow/deep marine environments: Shallow/deep marine environments Shallow marine environments Carbonate ramps exhibit processes and characteristics comparable to clastic shelves, with carbonate sands and muds ultimately producing a seaward transition from grainstone to mudstone, commonly with similar sedimentary structures Rimmed carbonate shelves consist of a coral reef or carbonate sand barrier at some distance from the mainland; the shelf lagoon can be up to many tens of kilometers wide Boundstones dominate the reef facies Shelf lagoon facies are mostly fine-grained and ultimately lead to the formation of mudstones and wackestones


Shallow/deep marine environments: Shallow/deep marine environments Deep marine environments The continental slope is a major source of sediment for the deep sea, and is a setting where slumps can occur Debris flows and turbidity currents are the main mechanisms of transport from the continental slope into the deep sea; these processes can be triggered by external forcing (e.g., an earthquake) or by the slope reaching a critical state as a result of ongoing deposition Debris-flow deposits and turbidites are often genetically related Turbidites can be both clastic (commonly leading to the formation of wackes) or calcareous


Slide21: Animation


Shallow/deep marine environments: Shallow/deep marine environments Deep marine environments Submarine canyons at the shelf edge (commonly related to deltas) are connected to submarine fans on the ocean floor Contrary to debris flows, turbidites exhibit a distinct proximal to distal fining Submarine fans share several characteristics with deltas; they consist of a feeder channel that divides into numerous distributary channels bordered by natural levees and are subject to avulsions Proximal fan (trunk channel) Medial fan (lobes) Distal fan


Shallow/deep marine environments: Shallow/deep marine environments Deep marine environments Basal Bouma-divisions have the highest preservation potential updip; upper Bouma-divisions are more common downdip Turbidite lobes characterize the medial fan and may exhibit the most complete Bouma sequences The Bouma-model is increasingly challenged, because many turbidites do not conform to it (e.g., ‘high-concentration turbidites’) Contourites are formed by ocean currents and commonly represent reworked turbidites


Shallow/deep marine environments: Shallow/deep marine environments Deep marine environments Pelagic sediments primarily have a biogenic origin Calcareous ooze (e.g., foraminifera) forms above the calcite compensation depth (CCD) at ~4000 m depth Siliceous ooze (e.g., radiolarians, diatoms) forms between the CCD and ~6000 m depth where silica dissolves; it lithifies into cherts Hemipelagic sediments consist of fine-grained (muddy) terrigenous material that is deposited from suspension Eolian dust is an important component (~50%) of hemipelagic (and pelagic) facies Black shales have a 1-15% organic-matter content and form in anoxic bottom waters