Tag: Riversediment

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You Have to be Swift

You Have to be Swift
You Have to be Swift

You Have to be Swift

Well a “White Throated Swift” if I read my audubon ID correctly. They are silly fast birds. Getting one launching from it’s home…. lol. My reaction time isn’t as fast as in my youth. As a geologists I’m less interested in the bird instead of the WONDERFUL geology behind it. I’m always thinking about Cretaceous river systems operating up here in the rock record. Geologists read rocks like a book. The local rocks make for a great story ! ..

Transition to geology:

Indeed this Swift is a cliff dweller exiting that dark subsoil homestead built out of the Cretaceous Hell Creek/Lance formation Cretaceous River bottom sediment exposed here. Those various “rocks” are all different kinds of mudstone “pebbles”. These were rolled down a very large paleo-river. Each rock torn up from the clay river bottom up stream then rounded along the way. There is a nice mix of clast sizes represented in the wall. The current velocity in that paleo-river obviously carried these pebbles to cobble sizes down river only to dump them here at this spot. That river lost it’s ability to carry this material leaving it behind for me to observe 66 million years later. No fossils in this debris which represents the source’s likely-hood of having bones in the clay. (way long discussion ommitted).

Somewhat more recently, rain water has very carefully washed the sand away from the pebbles showing this well exposed “cobblestone surface that is resultant from that pre-historic river depositional event. Notice I didn’t say “flood”. Floods wash sediment down stream as well as scouring clay chunks out of the floor of the stream. It’s the cessation of that flood that leaves this kind of debris as these transported mud clasts behind. Slower velocity drops the suspended and saltated load instantly. This pile of river gravel was eventually covered by another river cycle of deposition. The next depositional event overlapping rinse and repeat millions of times. The same river swept back and forth across the Cretaceous piedmont filling the epi-continenal sea at the time. Dinosaurs skinny dipped in these rivers sands/cobbles.

Location: Bliss Dinosaur Ranch, Wyoming/Montana borderlands (Wyotana)

Title: You Have to be Swift

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Triceratops Dinosaur Rib Excavation

Triceratops Dinosaur Rib Excavation
Triceratops Dinosaur Rib Excavation

Triceratops Dinosaur Rib Excavation (Tough Long Read)

There might be a few words to google here. My apologies ⚒⚒⚒. Geology has it’s nomenclatural requirements. To put all this in the big picture is the tough part.

Our Ranch by coincidence 🤔 is located upon a 700 feet thickness of Sandstone. It has exposures of the famous Hell Creek/Lance Formation (Cretaceous Period) The Uppermost Cretaceous was a period of life on a coastal plain similar topographically to the piedmont of North Carolina. Locally the climate was pretty lush, warm and wet. Meandering Huge Rivers choked with Sand / silt worn off the rapidly eroding mountains to the (current) west. The land lay of different orientation that currently.

North America appears to have been rotated 90 degrees west of how it’s positioned currently. Located around the equator with plate tectonics moving/rotating the continent to it’s current position over the intervening 66 million years. T-rex, Triceratops, Duckbills, ankylosaurs, all those dinosaurs kids know the names of lived here. Here one died…

This is higher up rock section toward the top of the Hell Creek formation not long before the massive “Bolide” (google this) struck the earth. Chicxulub Mexico sits on that big impact area. punctuated the extinction process already underway at the end of the Cretaceous. Big 80 percent of all species Extinction events. Extinction ultimately is initiated by a populations inability to reproduce .

There was a pizza oven effect from the radiant heat from all that Bolide ejecta re-entering the atmosphere. That effect didn’t help anything that wasn’t underground or in the water (mammals) as 20 percent of species survived this age. There is a discussion that dinosaur and other groups were waining in density/diversity near the actual time of the Bolide ended the age of Dinosaurs. Dinosaurs as a group died off but avian dinosaurs did not. (Birds are dinosaurs more or less just short tail and teeth). Eventually the environmental effects killed off the food web in the ocean too. Bad time on the planet for most.

SO:

This sediment is called Bentonite. Wyoming sells LOTS of Bentonite. Cooking it turns it white. Lots of industrial uses. Dave Love (a famous Wyoming Geologist) famously wrote/said: “Wyoming is a wonderful State, we can sell our dirt”. 🤘👀⚒ Bentonite is a clay rich volcanic ash as this is a lake deposit. This rib belonged to an animal that floated into a body of water. Spreading of this carcass did occur and one rib bone excavated was vertical as someone stepped on it and pushed it into the mud on edge. I found a raptor tooth mixed in the mud with this 20 percent Triceratops carcass. (It was Dromeosaur richardoestesia )

Above the Triceratops rib is it’s upside down fragment of pelvis. Another rib hides in the upper right corner of the frame. This was one of the smaller ribs collected on a smaller Tric. The little bottles are full of thin superglue which we consume by the pint. We have the tip off the end of it …. A rib like this will come out in 30 pieces and reassembled back at the ranch headquarters.

Location: Bliss Dinosaur Ranch, Wyoming/Montana borderlands.

Title: Triceratops Dinosaur Rib Excavation

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Triceratops Toe “Phalanx” Fossil

Triceratops Toe "Phalanx" Fossil

Triceratops Toe “Phalanx” Fossil sees the first light of day in “Some Time” 😜

The latest Cretaceous Age here on the Bliss Dinosaur Ranch was a time of fine grained sediment accumulation deposited from huge rivers. These rivers were sweeping back and forth across the landscape choked by the sand and finer grained sediment load they carried. Sand sized material was the rule for these rivers ability/capacity to carry things down river. This Triceratops Toe “Phalanx” Fossil survived it’s transport from the distant past to the present under my gentle brush.

With the exception of isolated small scale deposits like this, the Hell Creek/Lance Formation is largely barren of fossils. In 5.5 square miles of HellCreek/Lance formation on my ranch, only about an acre can be called ‘fossilferous”. That acre is the total of 25 smaller locations (microsites) and a bone bed Triceratops Toe “Phalanx” Fossil sits here “In situ”. (In place in the undesturbed bedrock).

This fossil is positioned in the outcrop deeper than you might suspect. Your looking at a toe bone physiologically behind a claw/nail. it is 4 more inches deeper into the outcrop so this is the top 2 inches of the bone exposed. Triceratops had big toes lolol. It’s deeper than it is long. I like to take photos of fossils in the outcrop as it’s sort of the “Eureka”/adrenaline rush moment.

Geologic Musings on this ranches “Dirt”:

Geologists consider the Cretaceous to have ended 66 million years ago. This toe bone has literally not seen the light of day in that unfathomable period of time. The sediment it is in, is a mix of sand, clay with chunky chunks (up to 2 feet) of torn up river bottom clays. The ripped up chunks of clay were rounded by bounding down a river/transport. There is a 2 foot thick or so blue clay pure of any fossil or other detritus directly under this 3 foot thick channel. That above that clay is a channel packed with chunks of clay/mud from upstream. . A mix of at least 3 different mud chunks from various sources nearby. I’ve seen chunks of mud angular like they got torn up 50 feet up stream. So this is a “channel” I’ve been following that tapers on either side that filled up with ripped up chunks of upstream river bottom mixed with a variety of bones from who ever was walking around at the time.

The bones were dropped here for me to find because the river waters slowed enough in this location to drop them out of suspension here mixed in among chunks of mud. The spaces between the “Cobbles of mud” are filled with sandy material that “Sifted in” from the flowing water. This is classic river sedimentation/deposit stuff. That is where you find the little fossils too. Sands mixed with smaller rounded pebbles of river bottom clay. It’s all part of the “Bed load” of a river and what is in it depends on river current velocity… (followed by a really long discussion lolol). IF the river is fast enough to move

Location: Bliss Dinoaur Ranch, Wyoming/Montana.