Lithified Detritus, long-time commenter and friend at ETEV, responded to ye olde beach rocks post by sending in beach rocks that, quite frankly, left me burbling incoherently. You know that feeling you get when you see something so awesome all you can do is make vaguely syllable-shaped noises and then attempt to breathe? Yeah, that’s what happened. Covet. Covet these rocks.
Anyway. Rocks and their story, by our own Lithified Detritus. Images and words belong to him. The puddles of saliva are mostly mine.
You asked for beach rocks. As you wish…
Beautiful beach rocks by Lithified Detritus I
This is from Presque Isle Park, in Marquette, MI. It’s a lovely place, with awesome beach rocks:
Beautiful beach rocks by Lithified Detritus II
The origin of these cobbles is close by – this is serpentinized peridotite of the Mona Formation, Archean in age – 2.6 billion years. Here it is pretty metamorphosed and intruded. it includes pillow formations.
Beautiful beach rocks by Lithified Detritus III
Higher up it is heavily weathered. More pillow lavas!
Beautiful beach rocks by Lithified Detritus IV
The pinkish stones in this shot are in fact sandstone, from the adjacent, and in fact overlying Jacobsville sandstone, a mere billion or so years old -dates are a little iffy.
Beautiful beach rocks by Lithified Detritus V
The Jacobsville contains no fossils, but in many places shows mud crack, ripple marks, and raindrop impressions. It is widely used as a building material in the U.P.
Beautiful beach rocks by Lithified Detritus VI
Pretty beach rocks!
Beautiful beach rocks by Lithified Detritus VII
That’s it. I am booking a damn flight to Marquette, Michigan. Who’s got a couch I can crash on?
For those of you wishing to send me their beach rock beauties, you can send ’em on to dhunterauthor at gmail dot com. I’ve seen your comments on combing and anticipate awesomeness. Bring it!
I’d forgotten all about the original beach rocks post. Still unsure whether what I saw was brick or sandstone, although given the location and local industry, it would not surprise me at all were it current tumbled brick.
LD’s pic of the serpentinized peridotite (eff you spellcheck those are too words) reminded me of stones we used to find along rivers back home, so I went checking and what do you know? Yup. Probably not exactly the same as what can be found in the Josephine Ophiolite (again, it’s a word damn you!), but that marbling and those bold colors are quite familiar.
The Jacobsville contains no fossils, but in many places shows mud crack, ripple marks, and raindrop impressions.
How does it happen that the mud gets turned to stone while preserving those soft features? I’ve tried a bit of Google-fu, but everybody seems to just hand-wave that part away from the explanation.
Lithified Detritus, thanks for looking this up for me. I read the pages available and I didn’t see a real blow-by-blow explanation, but it appears that simple drying creates a structure that is able to resist redissolving when the layer is later submerged. This runs counter to my experience in ceramics class – dried, but unfired pots are very easy to dissolve in water. Maybe sun baking acts as the “firing” that makes the structure water resistant? Or, could it be that a layer of dry-deposited sand or dust protects the features?
That central cobble in photo 5 is textbook serpentinised peridotite. I’ve worked in komatiites in the past (nickel exploration) and seen that exact texture in 2.7Ga adcumulates.
Nice!!! I love the colours and the patterns, most especially the lavaprints. Gorgeous!
Those teardrop shaped lava prints are wonderful!
I’d forgotten all about the original beach rocks post. Still unsure whether what I saw was brick or sandstone, although given the location and local industry, it would not surprise me at all were it current tumbled brick.
LD’s pic of the serpentinized peridotite (eff you spellcheck those are too words) reminded me of stones we used to find along rivers back home, so I went checking and what do you know? Yup. Probably not exactly the same as what can be found in the Josephine Ophiolite (again, it’s a word damn you!), but that marbling and those bold colors are quite familiar.
How does it happen that the mud gets turned to stone while preserving those soft features? I’ve tried a bit of Google-fu, but everybody seems to just hand-wave that part away from the explanation.
There doesn’t seem to be a lot out there that isn’t behind a paywall, but I did find this.
Lithified Detritus, thanks for looking this up for me. I read the pages available and I didn’t see a real blow-by-blow explanation, but it appears that simple drying creates a structure that is able to resist redissolving when the layer is later submerged. This runs counter to my experience in ceramics class – dried, but unfired pots are very easy to dissolve in water. Maybe sun baking acts as the “firing” that makes the structure water resistant? Or, could it be that a layer of dry-deposited sand or dust protects the features?
That central cobble in photo 5 is textbook serpentinised peridotite. I’ve worked in komatiites in the past (nickel exploration) and seen that exact texture in 2.7Ga adcumulates.
I loves my job