Bone beds. What are they? It is rare to come across a complete dinosaur skeleton – or even a partial skeleton. These are what scientists like which is why the recent discoveries in China and Argentina have taken such a prominent position in various pieces of research in journals etc. The media of course also like dinosaur skeletons and most of us have been impressed by specimens in natural history museums. However, most of the known accumulations of dinosaur bones occur somewhat differently – as disarticulated and broken bones, very often in jumbles of fragments and splinters that can never be realistically put back together. These have accrued as a result of natural processes, very often involving moving water, and piling up in bands as the water moves around obstacles, and forms eddies and areas of less turbulence. Over time such bone beds become more solid, buried in silts and sands, and what had once been mud. Bone beds are the overwhelmingly most common form of preservation of dinosaur bones – but you wouldn't know that by reading the literature aimed at the popular market. They also very often form single layers of microfossils and typically in long deposits in former river beds, or areas of water flow including coastal environments (tsunami waves perhaps or tidal surges). Changes in the flow of the water that is transporting the bones enables deposits to be left behind – according to the link at http://phys.org/print401704599.html
Most of the fossils in bone beds are unidentifiable as far as species are concerned. Such deposits are sieved to select the bigger specimens and numerous museums around the world have eye popping quantities of them in their vaults. Bone beds, like most fossil deposits, are quite challenging – unless you are committed or paid to research them.