Besides normal collecting activities like surface collecting, digging and diving, we also bring home or have shipped to us formation from various locations. We take that formation and depending of what it is made of break it down. If you have a nice clay or sandy formation you can just wash it down with water over a millimeter sieve. Harder materials like shale sometimes need chemicals to break down the material. Once the material is broken down and sieved you can search through it under magnification and find "micro fossils" from that location. Some locations are loaded with tons of awesome microfossils while some others are not. Below you can find reports on time when matrix was collected and searched for fossils.
Eocene Chadron Formation Oligocene Brule Formation White River Group Sioux County Nebraska
Miocene Sharktooth Hill Round Mountain Silt Ernst Ranch Kern Co. California
Miocene Sharktooth Hill Round Mountain Silt Ernst Ranch East Pit Kern Co. California
Oligocene Brule Formation White River Group Sioux County Nebraska
Oligocene Brule Formation White River Group Sioux County Nebraska 2
Pleistocene Melbourne Bone Bed Indian River Florida