The Yahatinda Formation is a geologic formation from

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

containing fossils dated to the

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

, specifically the late

Givetian The Givetian is one of two faunal stages in the Middle Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Eifelian Stage and followed by the Frasnian Stage. It is named after the town of Givet in ...

. The formation is largely made up of dolostones and dolomite though there are breccias and conglomerates located towards the based on the formation. It overlies the Cairn Formation and Flume Formation while underlying the

Eldon Formation The Eldon Formation is a stratigraphic unit that is present on the western edge of the Western Canadian Sedimentary Basin, Western Canada Sedimentary Basin in the southern Canadian Rockies of southwestern Alberta and southeastern British Columbia ...

. Not many fossils have been found within the Yahatinda Formation though

placoderm Placoderms (from Ancient Greek πλάξ 'plax'', ''plakos'''Plate (animal anatomy), plate' and δέρμα 'derma'''skin') are vertebrate animals of the class (biology), class Placodermi, an extinct group of prehistoric fish known from Pal ...

lobe-finned fish Sarcopterygii (; )—sometimes considered synonymous with Crossopterygii ()—is a clade (traditionally a class or subclass) of vertebrate animals which includes a group of bony fish commonly referred to as lobe-finned fish. These vertebrates ar ...

, and

jawless fish Agnatha (; ) or jawless fish is a paraphyletic infraphylum of animals in the subphylum Vertebrata of the phylum Chordata, characterized by the lack of jaws. The group consists of both extant taxon, living (Cyclostomi, cyclostomes such as hagfish ...

have been found. Two distinct environments are preserved within the formation being a river and coastal marine environments. The strata that suggest a river or delta environment are generally found in older layers of the formation than the marine beds.

History and naming

What is now known as the Yahatinda Formation was originally defined as the Ghost River Formation by Walcott in 1921. This original locality was made up of dolomites that lay above

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

- aged limestones located below the late Devonian Fairholme Group. However, due to the formation being poorly described by the original author, a number of ages were applied to it with these dates ranging between the Cambrian and Devonian. These previous issues with the age of the formation were remedied when Aitken (1966) published a more detailed description of the locality along with assigning the a large amount of the formation to the Cambrian with only the top being considered early Devonian. During this field work, separate plant-bearing beds were found nearby which would later be referred to as the Yahatinda Formation. The Yahatinda Formation is named after the Ya-Ha-Tinda Ranch which is located at the northern side of the Red Deer River. Both of these are located near the eastern border of the

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Description

The beds that make up the Yahatinda Formation, located on the west side of the Wapiti Mountain, have a thickness of and a width of . In areas outside of the type locality, the formation can reach a thickness of .Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. . The beds themselves are made up of two distinct facies being the channel and non-channel facies. The channel

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...

are made up of dolosiltite and pink to purple-red dolomite though breccias and conglomerate are also common. The facies are located in the deeper areas of the sub-Devonian channels. Fossil fragments of both fossil plants and animals have been found within the dolomite with this fauna being either

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

. Due to the alternation of texture in the grains and the presence of scour-and-fill structures, it is most likely that the channel facies represent a river ecosystem. The presence of mudcracks along with the fact that deposition only took place in the lower parts of the channels and valleys also suggest this

river delta A river delta is a landform, archetypically triangular, created by the deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or with a body of stagnant water. The creat ...

interpretation. The non-channel facies are represented by thinner sections that are made up of siltstones, dolosiltites, and dolomites. Throughout the beds, a number of stromatolites with a maximum diameter of have been found. The breccias and conglomerates are present under these facies. These two different facies are at different levels of the formation though show a transition with this transition ranging from smooth to abrupt. The age of the formation is based on the macroflora along with the spores found in the beds of the formation along with that dating of associated formations. The Yahatinda Formation is uncomfortably overlain by the Flume Formation which has been dated to between the latest Givetian and earliest Frasnian which gave previous authors an earliest age of before the latest Givetian. The Yahatinda Formation was later understood to represent the pertidal belt of the Gilwood member of the Watt Mountain Formation which suggests that the formation dates to between the middle to early late Givetian. The flora confirm this dating due to the presence of ''Aneurospora greggsi'', a spore common during the late Givetian and earliest Frasnian. The Yahatinda Formation is also overlain by the Cairn Formation, another late Devonian formation that is part of the Fairholme Group. The contact between the two formations is covered with

rubble Rubble is broken stone, of irregular size, shape and texture; undressed especially as a filling-in. Rubble naturally found in the soil is known also as 'brash' (compare cornbrash)."Rubble" def. 2., "Brash n. 2. def. 1. ''Oxford English Dictionar ...

. The Yahatinda Formation uncomfortably overlays the Eldon Formation, a middle Cambrian formation that gets truncated by the overlying formation. This unconformity is noticeable due to the sudden transition between the thickly bedded limestones of the Eldon Formation and the very thinly bedded dolostone of the Yahatinda Formation. It was deposited along the east side of the Western Alberta Ridge, a paleogeographic feature that existed at that time, and it is equivalent to the Cedared Formation that was deposited on the western side of the ridge. It is equivalent in age to the upper part of the

Elk Point Group The Elk Point Group is a stratigraphic unit of Early to Middle Devonian age in the Western Canada and Williston sedimentary basins. It underlies a large area that extends from the southern boundary of the Northwest Territories in Canada to Nort ...

in the basin to the east.

Paleobiota

Antiarchi

Arthrodira

Pteraspidiformes

Sarcopterygii

Palynomorphs

Progymnospermopsida

Paleoenvironment

The paleoenvironment of the non-channel beds of the formation transition between multiple distinct environments throughout the strata. The basal-most layers of the formation have been interpreted to be shallow marine

subtidal The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminate ...

intertidal The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various sp ...

low energy environment. Similar to these layers, the dolostone couplets also represent a low energy environment though these record a cycle between intertidal and supratidal environments. Throughout both of these strata, there is evidence of exposure to the air between preserved mudcracks and color molting. The breccia present in the lower areas is interpreted to be in deeper water that was never exposed to the open air. As the name suggests, the channel beds of the formation were either made by a river or delta.

References

{{Reflist Geologic formations of Alberta Devonian System of North America Devonian Alberta Givetian Stage Sandstone formations of Canada Siltstone formations of Canada Mudstone formations of the United States Conglomerate formations of Canada Fluvial deposits Tidal deposits Western Canadian Sedimentary Basin Devonian southern paleotropical deposits Fossiliferous stratigraphic units of North America Paleontology in Alberta