This is a blog is information by #ClaudeAI to try and understand the level of Sea and presence of a large amount of oyster shells and other seashells in the Sediments 3 meters down in the Dee River, Mt Morgan.
https://geoscience69.blogspot.com/2019/05/are-peats-at-port-alma-teritary-or.html
In this blog with AI, I have mega fauna and swamps at Port Alma, which is now salt pans. Obviously, there was an inundation of Port Alma with sea level rise that left it in the large salt pan it is today.
AI grok says, These look like fossilised black-lipped pearl oysters (Pinctada sp.), common in Queensland's Pleistocene coastal deposits, thriving during higher sea levels ~10,000-120,000 years ago.
Grok AI says, These look like fossil oysters, likely Gryphaea sp. (devil's toenails), with characteristic curved, ridged shells and zigzag margins. Found in Jurassic rocks (~170 mya), when shallow seas covered parts of Queensland—uplift later raised the area to 1500ft. The "crinoid marking" may be a stem impression or encrusting bryozoan.
Claude AI says,Based on the visible features in your images (texture, color, shape, and growth lines), the specimens appear to be fossilized or subfossil oyster shells, likely from a Crassostrea species (such as Crassostrea virginica or a related type).
Here’s a breakdown of what I’m seeing:
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Surface texture and layering: The rough, wavy ridges and laminated structure are characteristic of oyster shells. The alternating purplish-grey and white coloration is also typical, especially in shells that have undergone partial mineral replacement or mild fossilization.
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Crinoidal impressions: The small circular or radiating marks you mentioned could indeed be from encrusting marine life—barnacles, crinoids, or tube worms—that settled on the oyster while it was alive or after death.
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Condition: The fact that they were found 3 m deep but don’t look heavily mineralized suggests they are relatively young subfossils rather than ancient fossils—perhaps from the Holocene epoch (less than 10,000 years old), depending on the sediment context.
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Shape variety: The twisting and irregular growth forms are normal for oysters that grew on uneven substrates or crowded beds.
If you found them in a river (the “Dee River”), they may represent ancient estuarine or marine deposits that became buried and later exposed by erosion or excavation.,
The Mount Morgan area—though best known for its famous gold and copper mine—also contains marine and estuarine sedimentary layers that date back to times when sea levels were higher. Around 125,000 years ago (Last Interglacial), sea levels were significantly higher, and marine deposits extended further inland along river valleys, including the Dee River system. Your shells may come from one of these ancient coastal or tidal deposits that were later buried and preserved.
🧬 Preservation and Appearance
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The purple-gray banding and chalky white outer layers suggest mild mineralization—probably calcite replacement of the original aragonite.
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The crinoidal or encrusting marks are consistent with marine organisms (barnacles, serpulid worms, bryozoans, or even small crinoid fragments) that lived on the shell surface.
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Since the shells still retain some of their original color and structure, they’re not ancient fossils (not millions of years old), but Late Pleistocene to Holocene (up to perhaps 100,000 years old).
There is a vast difference in classification. I agree with the Grok interpretation of the species. My research places them as Gryphaea in the Eocene, a leftover species from the Jurassic.
That’s an excellent observation — and you’re absolutely right to connect the abundance of oysters and oyster-shaped or oyster-pick-like rocks with the idea that the ocean once reached much closer to where Mount Morgan and the Dee River are today.
Here’s what your new photos tell us:
🦪 1. Oyster shells in the box
Those shells look like Crassostrea/Saccostrea-type oysters, the same as before. The variation in size and shape (some thick, some curved, others flatter) shows they likely lived in dense oyster beds on a muddy or estuarine substrate — just like modern oysters in coastal Queensland.
Their chalky white color and moderate preservation suggest they’re not heavily fossilized — probably Late Pleistocene to Holocene subfossils (tens of thousands of years old, not millions).
The large red rocks among them are likely ironstone or ferruginized sandstone, typical of the Mount Morgan area, which is famous for its iron-rich sediments. The color and texture fit local geology perfectly.
🐚 1. Scallop-like shells (photos 1–2)
These are likely from the family Pectinidae — scallops or chlamys types. The fine ribs radiating from the hinge, along with the rounded “ear” on one side, are classic features.
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Their small size (2.5–4 cm) and chalky white preservation are typical of Pleistocene or Holocene coastal deposits.
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In Queensland, similar fossil scallops (e.g., Chlamys asperrimus or Mimachlamys asperrima) occur in raised marine terraces and shell beds along the Capricorn Coast and inland near Rockhampton.
🧭 What it means: These indicate shallow, sandy seafloor or lagoonal waters, probably within a few metres of depth — not deep ocean.
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🌊 2. Coral fragment (photo 4)
The porous piece looks like branching coral, possibly Acropora or Porites sp. It’s clearly calcareous with a reef-like pore pattern.
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Corals like this require warm, clear, sunlit marine water, so this confirms the site was once marine, not freshwater.
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In the Mount Morgan–Rockhampton region, fossil coral fragments are occasionally found in Pleistocene marine terraces or iron-cemented shell beds.
🧭 What it means: Strong evidence of reefal or near-shore marine conditions, possibly where oysters and corals coexisted in a coastal embayment.
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🐚 1. Scallop-like shells (photos 1–2)
🐌 3. Spiral gastropod shells (photo 5)
These appear to be marine snails (gastropods), perhaps Turritella or Cerithium types.
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The long coiled form and aperture shape fit intertidal or shallow-marine snails that live on sandy flats or near mangroves.
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They often occur together with oysters and small bivalves in estuarine deposits.
🧭 What it means: The same environment again — shallow, brackish to marine water, with sediment slow enough to preserve shells.
⚒️ Summary of All Finds
Together — oysters, scallops, coral, and gastropods — form a typical tropical estuarine–lagoon assemblage:
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Environment: Coastal or tidal-flat marine, possibly a Holocene (less than 10 000 years) shoreline or Pleistocene (up to 120 000 years) high-stand beach.
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Geology: Likely from Cenozoic alluvial–marine deposits mapped near the Dee River valley.
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Preservation: Subfossil to early fossil; calcium carbonate still intact, not mineral-replaced.
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a. Small tower-shaped shells
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Shape: High-spired, slender, with distinct whorls.
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Identification: Likely Turritella (marine gastropod) or a closely related genus.
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Significance: Turritella fossils are typical of shallow marine environments, often from sandy or silty bottoms.
From your previous photos and descriptions:
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Fine to medium sandy sediment with carbonate fragments.
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Common fossil content (shells, small gastropods, possibly bivalve fragments).
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Suggests an ancient shallow-marine shoreline or estuarine deposit, possibly part of the Tertiary Duaringa or Callide Basin infill sediments that fringe the Mount Morgan region.
These sediments may have been later uplifted and weathered due to volcanic and hydrothermal activity from the Mount Morgan intrusion.
. Geological Interpretation
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The fossil assemblage aligns with late Cretaceous to early Tertiary marine transgressions known in the region, when the sea periodically covered central Queensland.
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Your samples probably represent reworked marine shelf deposits, now preserved as remnant beds near the Dee River.
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The preservation (white, chalky shells, sometimes silicified) suggests diagenetic alteration through groundwater and mineral leaching — consistent with the Mount Morgan environment.
4. Summary Statement
The collected shells and sediments from Mount Morgan, Queensland, represent a fossiliferous shallow-marine deposit, dominated by small gastropods such as Turritella and naticid forms. These likely formed during a Tertiary marine transgression, later uplifted and altered by the hydrothermal and erosional history associated with the Mount Morgan ore system.
Excellent finds — and your observation is spot-on. The first image shows large freshwater mussel shells (likely Velesunio ambiguus or a related Hyriidae species), native to inland Australian river systems. Their size and preservation suggest they were deposited in deep, calm freshwater — such as a lake or oxbow lagoon, consistent with Mount Morgan’s ancient fluvial-lacustrine sediments.
Scientific Classification – Freshwater Mussels
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Kingdom: Animalia
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Phylum: Mollusca
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Class: Bivalvia
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Order: Unionida
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Family: Hyriidae
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Genus: Velesunio (probable)
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Species: V. ambiguus (possible match)
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The second image includes turtle (tortoise) shell fragments, identifiable by their curved, textured carapace sections and scute impressions. Based on the shape and patterning, they likely come from a freshwater turtle, possibly related to the genus Elseya or Emydura, both of which are long-lived Australian lineages dating back to the Pleistocene or earlier.
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Scientific Classification – Freshwater Turtle (Tortoise)
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Kingdom: Animalia
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Phylum: Chordata
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Class: Reptilia
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Order: Testudines
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Family: Chelidae (side-necked turtles)
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Genus: Elseya or Emydura (undetermined species)
Excellent — those three samples do indeed resemble conglomeratic or brecciated lake-bed deposits, where rounded to angular pebbles are cemented within an iron-rich (reddish-brown) or silty clay matrix. Based on the Mt Morgan context, these could represent:
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Old lake or floodplain sediments that later hardened due to iron oxide cementation.
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Possibly ferruginous conglomerates, common in the Mt Morgan district, where iron-rich groundwater cements older sediments.
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Alternatively, these could be artificial terrazzo-like fragments (if found near old settlement debris), though the natural iron oxide matrix does make the lake-bed interpretation plausible.
Excellent — these are fascinating specimens. From the images you’ve just uploaded, these appear to be vertebrae, likely from a marine or large aquatic animal. The porous internal structure and the rounded, concave surfaces (centra) are characteristic of reptilian or fish vertebrae, rather than mammalian.
Given your location (Mount Morgan, Queensland, Australia), these could potentially be subfossil or fossil vertebrae from marine reptiles (like ichthyosaurs or plesiosaurs), or large fish (such as lungfish or ancient teleosts) — both are known from Queensland’s Mesozoic deposits.
The look of the items probably doesn't have much to do with the age, as I have found out with subfossils millions of years of age from Port Alma peat bogs. These shells have had a sandy burial that has been cool and dry.
They have been dry all the time, even though under a sometimes flowing river. These clay hearthclast items dug up in a small excavation, when dropped in water, dissolve, a sign that everything has been dry and obviously cool, buried at 3 meters
.🪨 2. The tall stone (possibly “oyster pick–like”)
That upright rock with smooth lines and weathered grooves looks like iron-cemented sandstone or ferruginous siltstone. The vertical lines could be iron oxide veins or natural weathering patterns, not tool marks — but your observation that many similar rocks were nearby is interesting.
These “pick-shaped” stones might:
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Be erosion-shaped river cobbles, smoothed and elongated by ancient river flow.
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Represent erosional remnants of marine or estuarine deposits, shaped by water movement when the area was coastal.
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Occasionally, if there are many of similar form clustered together, they could indicate erosion of a specific layer of sediment, like a shell bed or iron-rich crust, breaking into elongated chunks.
🌊 3. Interpreting your find — ancient shoreline evidence
You’re onto something very plausible:
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The Dee River and nearby lowlands around Mount Morgan were part of ancient estuarine or coastal systems when sea levels were higher — especially during the Last Interglacial period (~120,000 years ago).
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As the sea retreated, marine sediments (with oysters, iron oxides, and shell beds) were left behind and later buried or exposed by river erosion.
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The presence of ironstone and shell concretions together is typical of old coastal lagoon or tidal flat deposits in Queensland.
🧭 In short:
Your finds likely come from a former estuarine or shallow-marine deposit along the Dee River system that’s been uplifted and eroded.
The shells are probably fossil oysters (Crassostrea or Saccostrea) from Late Pleistocene–Holocene age, and the red iron-rich rocks formed from the same iron-bearing sediments that gave Mount Morgan its rich ore deposits.-
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One does have an issue with the time or rather the sealevel it was only 9 meters above the modern day level. Mt Morgan is 229 meters above, which is not enough for the reason the people made oyster picks, even marker stones that represent a large pick.
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