#StrataDay

9 months ago

An offshore view, taken from a small boat in choppy seas, of deeply eroded coastal monoliths (or sea stacks) composed of distinctly layered Middle Ordovician carbonate rocks. The overall tone of the image is grey-blue, from the rough waters in the foreground, to the shoreline rock exposures in mid-right view, to the uniformly overcast skies in the background. Above the barren wave-swept shoreline, a forest of wind-blown spruce trees encroaches from the right.

Another archival entry for #Strataday: Coastal monoliths in the Middle #Ordovician (~460 MYA) Mingan Fm, #Mingan #Archipelago #National #Park #Reserve, #Quebec 🇨🇦. Differential erosion of Mingan Fm #limestones has sculpted these striking features. Scanned slide from a 1998 #GAC-MAC field excursion.

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9 months ago

Photograph of a man in a high vis jacket and a white hard hat looking at a grassy cliff composed of layers of terracota red mudstone and sandstone, and grey limestone.

#Strataday From the 2019 Oxford ES trip to Arran. A lovely marine-terrestrial-marine transition in this #Carboniferous heterolithic sequence. Connal for scale. This also reminded me of how much I miss teaching, especially on field trips. #geology ⚒️🧪

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9 months ago

At Vauréal Falls, Vauréal River in full flow plunges 76 metres over a cliff of grey interbedded shales and carbonates of the Upper Vauréal Formation. The river continues to flow away from the viewer down Vauréal Canyon beneath near vertical cliffs on the right. A steep talus slope extends from the base of the cliffs to the river's edge. Above the canyon, dense mixed forest continues to the horizon under grey, overcast skies. Image scanned from a 35 mm slide taken in May 1998.

Another 🇨🇦 #Strataday treasure: Late #Ordovician (~448 MYA) shales & carbonates of the upper Vauréal Fm at #VauréalFalls in #AnticostiNationalPark. Anticosti Island, #Quebec, was inscribed as a UNESCO World Heritage Site 2023 for its exceptional #fossil record across the end-Ordovician #extinctions.

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9 months ago

#Strataday!

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9 months ago

Aerial view of the Hudson Bay coast line east of Churchill, Manitoba. Looking approximately westward along a rocky ridge of dark coloured Proterozoic metasedimentary rock (Churchill "quartzite") on the right, with light tan coloured, gently shelving, Ordovician carbonate rocks in mid view. On the left, the dark waters of Hudson Bay extend to the horizon. A series of linear waves is breaking along the shoreline. Between the ridge on the right and the shelving Ordovician strata, an extensive boulder field of Churchill "quartzite" has developed. Where the two lithologies meet, the carbonate sediments have incorporated the much older boulders, some of which are very large (up to 12 metres x 4 metres).

A ground level view of the boulder field, with pale Ordovician carbonate rocks enveloping much older boulders of dark, deeply weathered metagreywackes in a spectacular ancient rocky shoreline setting. The fog shrouded waters of Hudson Bay lay off in the upper right background.

A view across the gently dipping Ordovician tan coloured carbonate rocks of the Churchill River Group, towards a dark ridge of Proterozoic Churchill "quartzite" in the distance. This just east of the main boulder field, and in the middle distance just a few large blocks of metagreywacke can be seen.

Down by the bay for #Strataday ... #HudsonBay, that is. Upper #Ordovician (~445 MYA) fossiliferous Churchill River Gp carbonates onlap & incorporate Proterozoic (~1.8 BYA) Churchill "quartzite" (metagreywacke) in a spectacular ancient #rocky boulder-strewn #shoreline. E of #Churchill, #Manitoba 🇨🇦

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9 months ago

A view looking approximately northeast past (on the left) a near-vertical cliff of horizontally interbedded marine carbonate and shales, stepping back in a series of erosional ledges. Across a deep valley in the mid-ground, tree-covered slopes of the facing mountain ridge are cut by a plunging creek bed. In the far background, another low mountain ridge with snow patches rises to a clouded sky.

A closer view of part of the upper mid-Cambrian succession, below the scene in the previous photo. In the lower part of the image, two persons can be seen standing on a talus slope adjacent to the near-vertical cliffs, amongst tall, narrow spruce trees and rough scrubby vegetation.

Upper middle #Cambrian (~503 MYA) basinal marine carbonate & shale deposits of the Chancellor Gp, including the informally named Duchesnay unit; Tangle Peak, near Miller Pass, #BritishColumbia 🇨🇦. Scanned slides from 1988 fieldwork. #Strataday

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Wild Places in the Southwest USA

9 months ago

Image is of a rugged coastline with low waves lapping onto shelving rocks in the foreground. In mid-frame, a group of five persons can be seen traversing a boulder-strewn inner shore, and in the background low, snow-covered cliffs rise to a clear blue sky.

Three warmly dressed people are standing in the mid-distance on an undulating surface of exposed limestone beds. Behind them is a vertical cliff about 10 metres high, exposing a section through weathered limestone strata. Snow covers part of the exposure on the left and in the mid-ground. Just above and to the right of the trio of geologists, the limestone layers are bowed gently upwards overlying a mound-shaped mass formed of the fossil remains of an extinct group of calcareous sponges known as archaeocyathans. This is an example of an early skeletal "reef" -- a wave resistant structure built on the Cambrian sea floor.

Back to #Newfoundland&Labrador for #Strataday, this time in #Labrador itself: #Cambrian (~515 MYA) Forteau Fm limestones, N shore of Strait of Belle Isle, E of Point Amour. Large mound-like structures are skeletal "reefs" built by #archaeocyathan #sponges. Slide scans from #fieldwork in June 1976.

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@kerrieneet.bsky.social

9 months ago

Beautiful #texture in outcrops of the Cretaceous Mancos Shale. Members: Muley Canyon Sandstone Member on top underlain by the Blue Gate Member with the Ferron Sandstone Member at the bottom

#photobyraykenny #strataday #BlueSkyArtShow theme #texture
#AlphabetChallenge #WeekTforTime #geology #rocks

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10 months ago

A shoreline exposure along the Bay of Fundy at low tide shows a section of cliffs (~30 meters high) formed by tilted beds of the lower portion of the Joggins Formation. The alternating hard and soft layers comprise interbedded sandstone, limestone, shale, and coal. The cliffs are topped by a thick deposit of non-indurated glacial till, supporting trees and scrub in the middle distance. An intertidal boulder field in the foreground is covered in a thick growth of brown algae. Several people can be seen at the far edge of the boulder field walking towards the cliffs.

This #Strataday we're at another 🇨🇦 #UNESCOWorldHeritageSite: #JogginsFossilCliffs, #NovaScotia, often referred to as a "Coal Age Galápagos" for the abundance & diversity of #Carboniferous (Pennsylvanian ~310 MYA) #fossils. Here, tilted beds of the Joggins Fm are capped by Pleistocene glacial tills.

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10 months ago

A mountain side made of layers of yellow and beige sandstone that as been tilted sideway nearly 90 degress. on some of the exposed sandstone surfaces there are current and wave ripples showing the sandstone was deposited in shallow water tidally influenced environment. There are lots of plants growing over different parts of the rock.

#Strataday 3.22 Ga tidal sandstones from the Moodies Group, South Africa. Nice ripples exposed on the left of the image. I've been looking for fossils in these rocks and will present our first results at @lifeandplanet.bsky.social in July. Outcrop is about 5 m high. #Geology #Paleontology

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10 months ago

A weathered limestone outcrop surface shows an impressive array of the large pygidia (tail shields) of the scutelluine trilobite, Ekwanoscutellum ekwanensis. About 10 fan-shaped pygidia are randomly oriented (upside down and rightside up) in an area measuring about 35 cm x 35 cm. Each pygidium features a short, bluntly tapered axial lobe from around which radiate a series of broad, smoothly rounded ribs.

Another accumulation of Ekwanoscutellum pygidia has been partly excavated from the reef margin. About a dozen complete and fragmentary tail shields are visible on the exposed limestone surface. These are randomly stacked on top of each other in an overlapping array; some are concave up (showing the ventral side) and others show the dorsal surface. A mapping compass sits to the right side and provides scale.

A grey, weathered surface of the exposed reef flank shows faint impressions of multiple Ekwanoscutellum pygidia. Sitting on the surface are two examples of freshly excavated tail shields, with multiple overlapping specimens in each. These are creamy brown in colour and contrast sharply with the old exposure. A marking pen at the right of the image is 14 cm in length and indicates how big the individual pygidia are.

An isolated cluster of Ekwanoscutellum pygidia excavated from one of the reef accumulations and photographed in the lab. The largest, almost fully exposed specimen in the lower centre measures 15 cm in axial length, indicating that the complete trilobite would have been at least 25 cm long.

A #TrilobiteTuesday follow-up to my last 2 #Strataday posts on the #Silurian Attawapiskat Fm, #HudsonBayLowlands. A major goal of #fieldwork was documenting & interpreting multiple accumulations of Ekwanoscutellum ekwanensis #pygidia: dozens of large tail shields nested together in #reef hollows!

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Britta Jensen

@tephrabird.bsky.social

10 months ago

TA Shaun, from VARG, in his element teaching the students about volcanic ash, you can see two clear in this picture, Mazama at his knee and he is looking at Mount St Helens Yn

A group of young Bighorn sheep by Athabasca Glacier - a classic site in the Rockies!

Student Lachlan looks to the distance inspecting end moraines with the Athabasca glacier behind him.

Saskatchewan River Crossing with the loess cap on the terrace to the right, full of silt, paleosols and tephra!

Next we stop at a favourite: Saskatchewan Crossing. #strataday. Loess, paleosols, and three (!) volcanic ash: Mazama, Mount St Helens Yn and Bridge River. Doesn’t get much better, unless you like glaciers. We finish at Athabasca Glacier. Beautiful but heart breaking in her steady retreat. 🧪⚒️

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@allochthonous.bsky.social

10 months ago

#Strataday!

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Chris Rowan

10 months ago

Standing on a flat inclined outcrop of reddish rocks on the banks of a river, on a sunny day. The stepped appearance is due to the exposure of different bedding surfaces, most of which have a rippled appearance. In the background, another exposure can be seen in the middle of the river. Trees and a factory can be seen on the far banks

For #strataday, some really impressive ripples in the Cambrian Monkton Quartzite, exposed on the banks of the Winooski River in Winooski, Vermont. Pretty much every bedding surface on this outcrop has a different style of ripple, in a different orientation. ⚒️

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10 months ago

An aerial view looking north across Houston Point, a low headland, and towards the dark blue open waters of Hudson Bay. The headland is nearly flat and almost devoid of vegetation. The tide is near high stand, flooding a broad expanse of rock-strewn shallows to the east, with a series of arcuate beach ridges framing the headland. Towards the centre of the headland low patches of pale rock are exposed, marking the remnants of ancient reef structures that have been almost completely removed by glaciation.

Over Houston Point, looking almost vertically down through an open helicopter window at a rocky exposure (seen at low tide) that is made up of roughly concentric ridges in an irregular bull's eye pattern. This is a "Philip structure" which marks the sagging of strata beneath the overlying load of a reef body which has subsequently been removed. The whole structure is about 150 metres across.

A lower level oblique view at Houston Point, looking across a Philip structure at ebbing tide with the open waters of Hudson Bay in the background. Irregularly concentric ridges are seen in the foreground, marking the edges of beds dipping gently towards the centre, where a portion of the deeply eroded reef core still remains.

A close-up view of the exposed Attawapiskat Formation at Houston Point. The white limestone is essentially a coquina made up of the undeformed shells of a large brachiopod -- Pentameroides septentrionalis. These formed extensive banks flanking the large reefs which have been removed by glacial action. Fragments of tabulate corals eroded from reefs are also present. The head of the geological hammer in the lower part of the image is about 18 cm long.

My last #Strataday featured exhumed 3D #Silurian (~435 MYA) Attawapiskat Fm reefs in n. #Ontario - this week we see the same unit in very different context. On Akimiski Is. in #HudsonBay the reef structures have been glacially scoured leaving only remnants - but incredibly #fossiliferous! #Nunavut 🇨🇦

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@lindamaryolivine.bsky.social

10 months ago

Photo of a coastal wave cut platform and cliffs on a sunny day. The platform is grey rock with bands of red knobbly rock and beige boulders. The lower part of the cliff is green from algae then red, brown and orange, the upper part is yellow brown. The ironstone shake was deposited on a storm dominated marine shelf during a lowering of local sea levels. The Staithes sandstone was deposited in a lower shore face marine setting during a fall, then subsequent rise of local sea levels. Both are highly fossiliferous.

#Strataday The early #Jurassic Ironstone Shales member of the Redcar Mudstone Formation (platform and lower half of cliff) and Staithes Sandstone Formation (upper half of cliff) exposed at #Saltburn , Redcar & Cleveland, UK, more deets in the alt text #geology

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Lindamary Fowler

10 months ago

Cleavage / bedding relationships. #OUGS Severnside trip to Llyn du Bach manganese mines, North Wales with Tom Cotterell, then at the National Museum of Wales. #Strataday

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10 months ago

#Strataday some urban stratigraphy

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10 months ago

#Strataday some cheeky outcrop sneaking on at the side. I wonder what the lithology is. I'm guessing sandstone.

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10 months ago

Another one for #strataday

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10 months ago

A nice addition for #strataday

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@clarkeocrinus.bsky.social

10 months ago

Small cliff of red brown sandstone in undulose layers with abundant angular pebbles of white and grey rock. The outcrop is surrounded by green temperate forest plants and there is abundant leaf litter on the floor.

Belated #Strataday one of the few #Permian outcrops in Belgium. Fluvial conglomerate red beds. Clasts are vein quartz, schist, and underlying devonian limestones. Outcrop is ~ 3 m high #Geology

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David Clark

10 months ago

A Devonian bioherm from Alpena, Michigan. Most of the layers are flat, but the middle is bulged where a Devonian coral reef flourished. Lots of nice crinoids come from this layer also.

#Strataday

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10 months ago

Aerial view from helicopter showing a large river channel (flowing left to right) excised in tundra lowlands. Spruce trees line the banks, with patches of muskeg in the background. A large island, and several smaller islets composed of pale grey rock, extend across the dark water of the channel in the middle of the image. Another patch of pale rock is exposed on the far shore behind the main island. Each of the roughly dome-shaped islets and the isolated shoreline outcrop is a single Silurian fossil reef, exhumed in full relief.

A person stands on an exposed rocky outcrop on the shore of a large river. The grey rocks rise about 4 metres above water level and curve gently inland forming a half-dome shape. The rough rocky surface shows the effects of erosion by ice and water. In the background, clear blue sky frames the standing figure.

A closer view of the buff-grey reef-associated limestone with an abundance of fossils exposed within a small open catchment area. Visible at the centre and right-centre are two phragmoceratid cephalopod shells; other fragmentary orthoconic cephalopods are scattered throughout the same pocket. A mapping compass sits on the surface for scale and orientation.

$Another close-up of a fractured area of reef surface showing an assortment of fragmentary favositid tabulate corals and cephalopod shells. A small scale gives an indication of size.$

Another close-up of a fractured area of reef surface showing an assortment of fragmentary favositid tabulate corals and cephalopod shells. A small scale gives an indication of size.

Another #Strataday look-back: slide scans from 1995 fieldwork on the early #Silurian (~435 MYA) Attawapiskat Fm. 3-D exhumed #reefs exposed along the Attawapiskat R, #HudsonBayLowlands, #Ontario w amazing #fossil preservation, esp. within reef crevices & cavities, incl. corals & cephalopod molluscs

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10 months ago

#Strataday

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@rubencomitini.bsky.social

10 months ago

Excellent. #Strataday on Sunday.

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Ruben Comitini

10 months ago

Marine sediments with strata of different colors (from almost white to brown-reddish and blue-grey). The strata on the bottom are fine-grained (probably the top of a turbidite sequence), while above them there are conglomerates (probably the base of deposits formed by another successive turbidity flow - other finer-grained strata above these are not visible in the picture).

For #StrataDay here are marine sediments from the Miocene of La Morra (Cuneo Province, Italy).

These are turbidites that include some fossiliferous lenses (not visible here) with mainly fossil plants and molluscs.

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