2 Materials that make up sediments Weathered RocksOrganic MaterialMineral Fragments
3 Ways sedimentary rocks can form Compaction and cementation of sedimentsEvaporation of a solutionPrecipitate from a solution
4 Kinds of sedimentary rocks 1) Clastic/DetritalComposed of fragments and small pieces of rock (clasts)sometimes show layeringMake up more than 85% of all sedimentary rocksEx) sandstone, siltstone, shale
5 Fragments Round Fragments = CONGLOMERATE Angular Fragments = BRECCIA (pronounced Brechia)(“cc” is “ch” like Gucci)
6 Types of ClastsThe formation of clastic rocks begins with the movement and relocation of fragments.The majority of these are moved by running water.Larger pebbles and gravels are often the first to be dropped and settle in shallow water near the shore.Next to settle are the smaller sands.Finally, in calm water, the silts and clays.
7 Formation of Clastic Rocks Loose sediments become solid rock when sediments become cemented.Ocean water, lake water, and ground water all contain natural cements in the form of dissolved mineral.Silica (SiO2), calcite (CaCO3), iron oxide (Fe2O3), and clay minerals.When minerals fill in the spaces between sand grains, pebbles, or other rock particles, they bind the fragments together through cementation.The type of cement influences the rock’s color.
8 2) OrganicContains the cemented (lithified) remains of once living thingsSometimes contain fossilsEx) coal
9 3) Chemical Form by precipitation or evaporation of a solution Often contain crystals or appear “dried up”Ex) rock salt
10 4) BioclasticComposed of broken shell fragments and similar remains of living organismsEx) limestone
11 Features of Sedimentary Rocks StratificationThe arrangement of visible layers.The most characteristic feature of sedimentary rocks.Results from the change in the type of sediment being laid down in one place.FossilsThe remains, impression, or any other evidence of a plant or animal preserved in rock.Occurs when a dead organism is buried by sediment that gradually turns into rock.The soft parts of the organism decay; the hard parts become rock.
13 Features of Sedimentary Rocks Ripple MarksCommon feature of sedimentary rocks.Sand patterns formed by the action of winds, streams, waves, or currents.Ripple marks are generally preserved in sandstone.Mud CracksDevelop when deposits of wet clay dry and contract.The cracks are filled in with different solutions and fossilize.Generally form in shale.
15 Features of Sedimentary Rocks NodulesHard lumps of fine-grained silicaFound in limestone and chalk.ConcretionsRound solid masses of calcium carbonate.Found in shale.Both Nodules and Concretions form when minerals in a solution precipitate around a fragment in the clay sediment.