Hilda mega-bonebed
The Hilda mega-bonebed is significant because the behavior of the preserved dinosaurs themselves was the dominant cause of its existence, rather than the stratum's geological history like most bonebeds.
Secondly, the modern Hilda area lacks the rough badland terrain that breaks up many probably equivalent deposits in Dinosaur Provincial Park.
[4] In 1996, the Royal Tyrell Museum finally performed a preliminary survey of the area studied by Langston and Taylor and entire new bonebeds were discovered.
[8] The research at Hilda was so complex that over ten years passed from the start of the project until David A. Eberth, Donald B. Brinkman, and Vaia Barkas published a formal description in the scientific literature.
[9] The mega-bonebed is located 25 kilometers west of the town of Hilda, Alberta in a "steep-walled" valley cut into the landscape by glaciers during the Pleistocene epoch.
[11] The researchers estimated the entire Hilda complex to be 2.3 square kilometers in area based on the length of its north-south and east-west axes.
[19] When the researchers examined the stratigraphy of the Hilda site they found that the fourteen bonebeds occupied identical positions in the stratigraphic column.
The first of these was H97-09, a natural part of the same stratum that hosted the ceratopsian bonebeds, but bearing only the remains of aquatic animals like champsosaurs, crocodilians, fish, and turtles.
[8] At the conclusion of their research program, Eberth, Brinkman and Barkas were unable to identify the bonebeds' ceratopsian remains to a rank more specific than the subfamily Centrosaurinae.
[13] In H97-02 the researchers found that at least 6 individuals were discovered in a 20 square meter area, but suspected that this relatively high density was not uniform throughout the deposit.
Therefore the original size of the centrosaur herd was probably even larger than the estimate based on still-accessible fossils would suggest and may have included up to several thousand dinosaurs.
[26] The mudstone hosting the Hilda mega-bonebed preserves large quantities of plant fossils throughout the bed as well as coal, wood debris, and root traces.
[25] Previous research on Albertan centrosaur bonebeds interpreted their formation in terms of a herd of dinosaurs drowning while trying to cross a swollen river.
[16] Eberth, Brinkman, and Barkas proposed a different explanation for the Hilda mega-bonebed, hypothesizing that a herd of Centrosaurus apertus, as well as other local wildlife, were killed by a flood.
[25] Chemical reactions between the decaying dinosaur flesh and floodwaters caused iron to precipitate out of the water and formed the ironstone concretions commonly found in the mudrock hosting the mega-bonebed.
[28] Eberth Brinkman and Barkas observed evidence that the sediment was deformed and contorted near the top and bottom before it hardened into the mudstone it is today.
[5] Monodominant bonebeds of horned dinosaurs like Styracosaurus, Pachyrhinosaurus and Centrosaurus are common in late Cretaceous strata of central and southern Alberta.
This difficulty emerges from the complicated nature of local stratigraphy as individual bonebeds are difficult to track for more than a few hundred meters because they are divided by ancient channel deposits.
In two 2005 scientific papers, Eberth, Getty, and Currie formulated a hypothesis for the formation of the centrosaur bonebeds of Dinosaur Provincial Park.
They envisioned common flooding events drowning large numbers of local wildlife, including herds of Centrosaurus and Styracosaurus.
[28] The process of reworking and reburial might have occurred over decades or millennia before the remains were buried for good in their final resting place, which was often in deposits left by channels of flowing water.
[28] Eberth, Brinkman, and Barkas thought that the above scenario "appl[ied] particularly well" so the Hilda bonebeds formed as a result of similar processes to those of Dinosaur Provincial Park.
[34] The Hilda mega-bonebed may also support the previously suggested notion that some kinds of centrosaurines participated in seasonal migrations, travelling from east to west.
[35] Brinkman and others proposed this hypothesis in 1998 to explain why ceratopsians represented a greater portion of ornithischian biodiversity at sites like Unity, Saskatchewan or Onefour, Alberta near the ancient coast, while the famous centrosaur bonebeds of Dinosaur Provincial Park were all preserved in more inland habitats.
Eberth, Brinkman, and Barkas noted that Hilda is located roughly halfway between the ancient coast and the Dinosaur Provincial Park bonebeds.
