Trepassey Formation

Trepassey Formation
Stratigraphic range: Ediacaran 565–560 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Trepassey Bay, the locality after which the formation is named.
Type	Formation
Unit of	St John's Group[1][2]
Sub-units	See: Members
Underlies	Fermeuse Formation[2]
Overlies	Mistaken Point Formation[3][2]
Thickness	300 m (984 ft)
Lithology
Primary	Gray Sandstone[2]
Other	Shale, Tuff, Mudstone, Siltstone, Agglomerate
Location
Coordinates	46°40′N 53°20′W / 46.66°N 53.34°W / 46.66; -53.34
Region	Newfoundland
Country	Canada
Type section
Named for	Trepassey Bay
Occurrence in southeast NL

The Trepassey Formation is a geologic formation that crops out in Newfoundland, which consists of gray sandstones and rare tuffaceous rocks. It also preserves fossils dating back to the Ediacaran period, which were buried on a deep ocean marginal slope.

Geology

The Trepassey Formation is primarily composed of a series of thin-bedded, fine-grained turbidites, a type of deposit found in deep ocean areas.^[4] It is sharply and conformably overlain by the shale dominated Fermeuse Formation, and conformably underlain by the argillaceous Mistaken Point Formation.^[5]

Facies

The formation contains up to known six facies, which are as follows:

• Facies 1: This facies only gets up to 90 cm (35.4 in) thick in some areas, and is composed of grains which range from sizes of silt to very fine sand. Overlying these facies are green mudstones, which are structureless in nature.^[4]

• Facies 2: This facies has an unknown thickness, but features rippled cross-lamination, which are overlain by draping or flat lamination and structureless mudstones, and contains grains with sizes ranging from very fine to medium sand. Where the ripples are visible, they are always going toward a southern to south-western direction. There are also some areas of this facies that contains rare structureless sandstones.^[4]

• Facies 3: Parts of this facies is entirely restricted to this formation and contains two beds, 3A and 3B. 3A only gets up to 50 cm (19.7 in) thick, and is composed of yellowish-green sandstone, which itself contains medium to coarse-grained, angular to sub-rounded quartz and feldspar grains, and is the restricted bed. At the base of 3A there can also be found dark-gray mudstone clasts, usually up to 3 cm (1.2 in) long. Meanwhile, 3B is not measured, but is composed of structureless beds that contain high amounts of ash.^[4]

• Facies 4: This facies is not measured, and contains thin crystalline tuff layers, and are far less common than is seen in the underlying Mistaken Point Formation.^[4]

• Facies 5: Similar to Facies 4, this facies rarely appears in the formation, only occurring at the very top. It is not measured, and contains intraformational tubular mudstone clasts that can range from 2–50 cm (0.8–19.7 in) long, alongside laminated mudstones.^[4]

• Facies 6: This facies is very thin, only getting up to a few centimetres in thickness, and is primarily composed of laminated mudstones. The thickness of the facies is notably uniform, and contains irregular silt-sized grains, separated by clay and a black carbonaceous material, which may possibly be the remains of microbial mats.^[4]

Members

The formation has also been split into two members, which are as follows, in ascending age:

• Catalina Member: This lower member, which has only been measured in one area up to 50 m (160 ft) thick,^[6] is primarily composed of the mudstone and siltstone bearing facies and beds, as well as occasional sandstones. These are predominately greenish-gray in colour, and are thin to medium-bedded. In the upper sections of this member, there can also be found cross-stratified sandstone. This member is also the fossiliferous of the two.^[5]

• Port Union Member: This upper member, which can get up to 94 m (308 ft) thick,^[6] is dominated by the sandstone facies and beds. These gray sandstones are fine to very-coarse-grained, and is primarily quartzo-feldspathic in nature. There are also interbedded layers of mudstone, sandstone, agglomerate, and tuff. The coarser layers of this member are volcanogenic in nature, containing a mixture of pyroclastic debris and sediments, which does not allow for the preservation of fossil material.^[5]

Paleoenvironment

The environment of the Trepassey Formation, at the time of its deposition, was on a deep ocean marginal slope. This has been inferred from the finer grains and southern palaeocurrent, which is consistent with marginal slope environments, especially ones that sit just above the turbidity currents, fast moving water, that would have carried much coarser grained material.^[4] There are also slumped units present within the formation, hinting towards the presence of an appreciable slope, which further suggests that the Trepassey Formation was deposited on a very steep marginal slope.^[4]

Paleobiota

Like the other overlying and underlying formations, the Trepassey Formation represents a rare deep-marine paleoenviroment, situated on a slope,^[7] which was home to various sessile forms, like the petalonamids Fractofusus and Trepassia, and even rare examples of organisms related to modern animals, like the staurozoan cnidarian Mamsetia, previously the paratype of Haootia.^[8]

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Petalonamae

Genus	Species	Notes	Images
Arborea[9]	A. spinosa	Sessile frondose organism, A. spinosa was previously described as a species of Charniodiscus.[5]
Avalofractus[10][11]	A. abaculus	Sessile frondose organism.
Beothukis[10][11]	B. mistakensis	Sessile frondose organism.
Bradgatia[11][5]	B. linfordensis	Sessile frondose organism.
Charnia[10][11][5]	C. masoni	Sessile frondose organism.
Charniodiscus[11][5]	Charniodiscus sp. C. procerus	Sessile frondose organism.
Fractofusus[5]	F. andersoni	Sessile spindle-like frondose organism.
Pectinifrons[12]	P. abyssalis	Sessile comb-like organism.
Primocandelabrum[5]	Primocandelabrum sp.	Sessile frondose organism.
Trepassia[10][11]	T. wardae	Sessile frondose organism.
Vinlandia[13]	V. antecedens	Sessile frondose organism, previously reported as a species of Charnia.[5]

Cnidaria

Genus	Species	Notes	Images
Haootia[14]	H. quadriformis	Staurozoan cnidarian.
Mamsetia[8]	M. manunis	Staurozoan cnidarian.

incertae sedis

Genus	Species	Notes	Images
Aspidella[5][15]	A. terranovica	Enigmatic discoidal fossil.
Hadrynichorde[5]	H. catalinensis.	Sea Whip-like frondose organism.
Palaeopascichnus[1][16]	Palaeopascichnus sp.	Palaeopascichnid organism.
Lydonia[17]	L jiggamintia	Ovate sponge-like organism, previously assigned to some Blackbrookia specimens.

Ivesheadiomorphs

Genus	Species	Notes	Images
Ivesheadia[5]	I. lobata	Poorly preserved organism.
Blackbrookia[5]	Blackbrookia sp.	Poorly preserved organism.

Ichnogenera

Genus	Species	Notes	Images
Neonereites[16]	Neonereites sp.	Burrows.

See also

• Earth sciences portal
• Canada portal
• Paleontology portal

• List of fossiliferous stratigraphic units in Newfoundland and Labrador

References

1. A.G. Liu; D. McIlroy (September 2014). "Horizontal Surface Traces from the Fermeuse Formation, Ferryland (Newfoundland, Canada), and their Place within the Late Ediacaran Ichnological Revolution" (PDF). Geological Association of Canada - Special Paper (9).^{[dead link]}
2. "GEOLOGY OF THE AVALON PENINSULA, NEWFOUNDLAND" (PDF).
3. "Newfoundland and Labrador Map". Geoscience Atlas. Retrieved 2024-07-22.
4. Wood, Donald A; Dalrymple, Robert W; Narbonne, Guy M; Gehling, James G; Clapham, Matthew E (1 October 2003). "Paleoenvironmental analysis of the late Neoproterozoic Mistaken Point and Trepassey formations, southeastern Newfoundland". Canadian Journal of Earth Sciences. 40 (10): 1375–1391. doi:10.1139/e03-048.
5. Hofmann, H. J.; O'Brien, S. J.; King, A. F. (January 2008). "Ediacaran biota on Bonavista Peninsula, Newfoundland, Canada". Journal of Paleontology. 82 (1): 1–36. Bibcode:2008JPal...82....1H. doi:10.1666/06-087.1.
6. Mason, Sara J.; Narbonne, Guy M.; Dalrymple, Robert W.; O'Brien, Sean J. (February 2013). "Paleoenvironmental analysis of Ediacaran strata in the Catalina Dome, Bonavista Peninsula, Newfoundland". Canadian Journal of Earth Sciences. 50 (2): 197–212. doi:10.1139/cjes-2012-0099.
7. Wood, Donald A; Dalrymple, Robert W; Narbonne, Guy M; Gehling, James G; Clapham, Matthew E (1 October 2003). "Paleoenvironmental analysis of the late Neoproterozoic Mistaken Point and Trepassey formations, southeastern Newfoundland". Canadian Journal of Earth Sciences. 40 (10): 1375–1391. Bibcode:2003CaJES..40.1375W. doi:10.1139/e03-048.
8. McIlroy, D.; Pasinetti, G.; Pérez-Pinedo, D.; McKean, C.; Dufour, S. C.; Matthews, J. J.; Menon, L. R.; Nicholls, R.; Taylor, R. S. (September 2024). "The Palaeobiology of Two Crown Group Cnidarians: Haootia quadriformis and Mamsetia manunis gen. et sp. nov. from the Ediacaran of Newfoundland, Canada". Life. 14 (9): 1096. Bibcode:2024Life...14.1096M. doi:10.3390/life14091096. ISSN 2075-1729. PMC 11432848. PMID 39337880.
9. Pérez-Pinedo, Daniel; McKean, Christopher; Taylor, Rod; Nicholls, Robert; McIlroy, Duncan (20 January 2022). "Charniodiscus and Arborea Are Separate Genera Within the Arboreomorpha: Using the Holotype of C. concentricus to Resolve a Taphonomic/Taxonomic Tangle". Frontiers in Earth Science. 9 785929. Bibcode:2022FrEaS...9.1393P. doi:10.3389/feart.2021.785929.
10. Narbonne, Guy M.; Laflamme, Marc; Greentree, Carolyn; Trusler, Peter (July 2009). "Reconstructing a lost world: Ediacaran rangeomorphs from Spaniard's Bay, Newfoundland". Journal of Paleontology. 83 (4): 503–523. Bibcode:2009JPal...83..503N. doi:10.1666/08-072R1.1.
11. Mckean, Christopher; Taylor, Rod S.; Mcilroy, Duncan (December 2023). "New taphonomic and sedimentological insights into the preservation of high-relief Ediacaran fossils at Upper Island Cove, Newfoundland". Lethaia. 56 (4): 1–17. doi:10.18261/let.56.4.2.
12. Bamforth, Emily L.; Narbonne, Guy M.; Anderson, Michael M. (2008), "Growth and Ecology of a Multi-branched Ediacaran Rangeomorph from the Mistaken Point Assemblage, Newfoundland", Journal of Paleontology, 82 (4): 763–777, doi:10.1666/07-112.1, S2CID 128922154
13. Brasier, Martin D.; Antcliffe, Jonathan B.; Liu, Alexander G. (September 2012). "The architecture of Ediacaran Fronds". Palaeontology. 55 (5): 1105–1124. Bibcode:2012Palgy..55.1105B. doi:10.1111/j.1475-4983.2012.01164.x.
14. Liu, Alexander G.; Matthews, Jack J.; Menon, Latha R.; McIlroy, Duncan; Brasier, Martin D. (22 October 2014). "Haootia quadriformis n. gen., n. sp., interpreted as a muscular cnidarian impression from the Late Ediacaran period (approx. 560 Ma)". Proceedings of the Royal Society B: Biological Sciences. 281 (1793) 20141202. doi:10.1098/rspb.2014.1202. PMC 4173675. PMID 25165764.
15. Gehling, James G.; Narbonne, Guy M.; Anderson, Michael M. (September 2000). "The first named Ediacaran body fossil, Aspidella Terranovica". Palaeontology. 43 (3): 427–456. Bibcode:2000Palgy..43..427G. doi:10.1111/j.0031-0239.2000.00134.x.
16. Liu, Alexander G.; Kenchington, Charlotte G.; Mitchell, Emily G. (June 2015). "Remarkable insights into the paleoecology of the Avalonian Ediacaran macrobiota". Gondwana Research. 27 (4): 1355–1380. Bibcode:2015GondR..27.1355L. doi:10.1016/j.gr.2014.11.002. hdl:1983/ef181134-4023-4747-8137-ed9da7a97771.
17. Pasinetti, Giovanni; Menon, Latha; Chida, Nagi; Olschewski, Pascal; McKean, Christopher; Pérez-Pinedo, Daniel; Taylor, Rod S.; McIlroy, Duncan (2025). "The macrofossil Lydonia jiggamintia gen. et sp. nov. from the Ediacaran of Newfoundland (Canada): From pseudofossil to metazoan-grade organism". Palaeontologia Electronica. doi:10.26879/1386.