Questions about archaic marine reptile and ammonite fossils from Paleocene sections of the Hornerstown Formation, U.S., and Takatika Grits, New Zealand

[Joseph Fossil]

To pass some time I've been recently researching early Paleocene life and I keep coming back to researching (in my view) the two strangest and controversial Late Cretaceous-Early Paleocene Formations I know of. These are the Hornerstown Formation dating 66.5-65.5 Million Years ago in what is now New Jersey, U.S. And the Takatika Grit Formation dating 66.5-60.0 Million Years ago in what is now the Chatham Islands, New Zealand. 

https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=0b3baee9ab1afc7973337f5047495b723fcfa4f2

https://www.researchgate.net/publication/315461615_The_age_of_the_Takatika_Grit_Chatham_Islands_New_Zealand

https://www.sciencedirect.com/science/article/abs/pii/S0195667109000184?via%3Dihub

 

 

I've read many reports about these formations and the pretty controversial stuff that's been found in both these areas (Paleocene ammonites and reports of archaic marine reptiles like Paleocene Mosasaurs). I'm really not 100% sure what to make of this as I've heard conflicting hypotheses on whether these more archaic marine reptile fossils were reworked from older formations while others say it's not too too likely? 

https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/maastrichtian-ammonites-from-the-hornerstown-formation-in-new-jersey/4F051D07668B7B893EEFECF0506E2F1B

https://bioone.org/journals/acta-palaeontologica-polonica/volume-57/issue-4/app.2011.0068/Short-Term-Survival-of-Ammonites-in-New-Jersey-After-the/10.4202/app.2011.0068.full

 

 

For most of these "controversial" specimens, I would say reworking is likely while some I'll admit I'm not sure? For the Mosasaurs, it's clear that the astroid impact 66 Million Years ago caused their total extinction, but I'm still not 100% convinced that none emerged from the event alive (at least barely) and swam the seas in the very first days of the Danian Paleocene but not too long after. Unlike the mostly terrestrial Non-Avian Dinosaurs, which could only hide in so many places and it's very unlike more than a tiny amount of individuals (not enough to support a population) made it into the Paleocene, the Oceans have slightly more areas to hide and more  even for endothermic air breathing animals like Mosasaurs (though as an endotherm, food does become a major issue especially when the ocean food chain nearly collapsed completely).

 

 

What I'm wondering is how valid are at least "some" of these supposed archaic marine reptile and ammonite fossils from the earliest Paleocene sections of the Hornerstown Formation and the Takatika Grit?

 

Also, of all the Maastrichtian Mosasaurs known so far, which ones would have been the mostly likely to have (at least briefly) survived the Cretaceous-Paleocene Extinction Event of 66 Million Years ago (would it have been generalist feeders, ones that specialized in deep sea hunting, ones with cosmopolitan distributions, ones small by mosasaur standards but still around the same size of the few confirmed large reptiles that survived the event like the 8 meter (26 feet) in length Thoracosaurus, or ones with all these traits and advantages)? 

[Al Dente]

2 minutes ago, Joseph Fossil said:

What I'm wondering is how valid are at least "some" of these supposed archaic marine reptile and ammonite fossils from the earliest Paleocene sections of the Hornerstown Formation and the Takatika Grit?

 

The Cretaceous/Paleocene boundary is now defined by the iridium layer. The problem with this is iridium may migrate up or down the sediments over time. An ammonite that was deposited beneath the iridium layer in the Cretaceous may now be considered Paleocene because the iridium at that particular site has migrated downward, therefore the Cretaceous/Paleocene boundary has migrated downward at that site.

[FossilDAWG]

There is good evidence that a few ammonites survived briefly (on the order of hundreds of thousand years at most) into the Danian, the earliest stage of the Paleocene.  For example, rare ammonites are found in the Danian (earliest Paleocene) at Stevns Klint, Denmark.  Other reports of Danian ammonites are more controversial.  Many lines of evidence indicate a rapid change in marine food webs following the terminal Cretaceous event.  It seems not improbable to me that a few ammonites might have initially survived the end of the Cretaceous, but were unable to adapt rapidly enough to long term changes in food availability and other ecosystem changes in the reconfigured post-Cretaceous marine environment.

 

I am not aware of compelling evidence for survival of large marine reptilian predators beyond the end of the Cretaceous.  They would likely have been even more sensitive than ammonites to changes in food availability.

 

Don

[Tidgy's Dad]

2 hours ago, FossilDAWG said:

There is good evidence that a few ammonites survived briefly (on the order of hundreds of thousand years at most) into the Danian, the earliest stage of the Paleocene.  For example, rare ammonites are found in the Danian (earliest Paleocene) at Stevns Klint, Denmark.  Other reports of Danian ammonites are more controversial.  Many lines of evidence indicate a rapid change in marine food webs following the terminal Cretaceous event.  It seems not improbable to me that a few ammonites might have initially survived the end of the Cretaceous, but were unable to adapt rapidly enough to long term changes in food availability and other ecosystem changes in the reconfigured post-Cretaceous marine environment.

Yes, a good example of a Dead Clade Walking. or extinction debt.

[Joseph Fossil]

5 hours ago, Al Dente said:

 

The Cretaceous/Paleocene boundary is now defined by the iridium layer. The problem with this is iridium may migrate up or down the sediments over time. An ammonite that was deposited beneath the iridium layer in the Cretaceous may now be considered Paleocene because the iridium at that particular site has migrated downward, therefore the Cretaceous/Paleocene boundary has migrated downward at that site.

 

@Al Dente Thanks bro! I actually never knew that Iridium migrates a little in sediment before!!

[Joseph Fossil]

5 hours ago, FossilDAWG said:

There is good evidence that a few ammonites survived briefly (on the order of hundreds of thousand years at most) into the Danian, the earliest stage of the Paleocene.  For example, rare ammonites are found in the Danian (earliest Paleocene) at Stevns Klint, Denmark.  Other reports of Danian ammonites are more controversial.  Many lines of evidence indicate a rapid change in marine food webs following the terminal Cretaceous event.  It seems not improbable to me that a few ammonites might have initially survived the end of the Cretaceous, but were unable to adapt rapidly enough to long term changes in food availability and other ecosystem changes in the reconfigured post-Cretaceous marine environment.

 

I am not aware of compelling evidence for survival of large marine reptilian predators beyond the end of the Cretaceous.  They would likely have been even more sensitive than ammonites to changes in food availability.

 

Don

 

@FossilDAWG Good points dude. I was wondering where in Denmark those Paleocene Ammonites (I think members of Baculites and Hoploscaphites) were found, so thanks bro. As for the Mosausaurs, the only ones I believe had a slight chance of being a Dead Clade Walking during the earliest days of the Paleocene are Halisaurus, Plioplatecarpus (which was medium sized and had large eyes which would have been useful for deep sea hunting), and the Takatika Grit Mosasaurid (and maybe even the pretty small Xenodens from the Maastrichtian of Morocco).

[Joseph Fossil]

5 hours ago, FossilDAWG said:

There is good evidence that a few ammonites survived briefly (on the order of hundreds of thousand years at most) into the Danian, the earliest stage of the Paleocene.  For example, rare ammonites are found in the Danian (earliest Paleocene) at Stevns Klint, Denmark.  Other reports of Danian ammonites are more controversial.  Many lines of evidence indicate a rapid change in marine food webs following the terminal Cretaceous event.  It seems not improbable to me that a few ammonites might have initially survived the end of the Cretaceous, but were unable to adapt rapidly enough to long term changes in food availability and other ecosystem changes in the reconfigured post-Cretaceous marine environment.

 

I am not aware of compelling evidence for survival of large marine reptilian predators beyond the end of the Cretaceous.  They would likely have been even more sensitive than ammonites to changes in food availability.

 

Don

 

@FossilDAWG Also, I heard that Piloplatecarpus fossils have been found at Stevns Klint, Denmark. Do you know by chance the age of those Piloplatecarpus remains?

[Joseph Fossil]

6 hours ago, Al Dente said:

 

The Cretaceous/Paleocene boundary is now defined by the iridium layer. The problem with this is iridium may migrate up or down the sediments over time. An ammonite that was deposited beneath the iridium layer in the Cretaceous may now be considered Paleocene because the iridium at that particular site has migrated downward, therefore the Cretaceous/Paleocene boundary has migrated downward at that site.

 

@Al Dente Also, do you know anyone on the fourm that has gone fossil hunting at the Hornerstown Formation?

[Doctor Mud]

12 hours ago, Al Dente said:

 

The Cretaceous/Paleocene boundary is now defined by the iridium layer. The problem with this is iridium may migrate up or down the sediments over time. An ammonite that was deposited beneath the iridium layer in the Cretaceous may now be considered Paleocene because the iridium at that particular site has migrated downward, therefore the Cretaceous/Paleocene boundary has migrated downward at that site.

That makes sense. I suppose the key is “sediment” before it turned to rock.

I know that this is true for plutonium in lake sediments over decades. Plutonium has been considered as a chrono marker for the Anthropocene, but could have the same problem. Migrating down into older sediments.

There are small but detectable amounts of plutonium from nuclear testing everywhere, even in pristine New Zealand lakes.  
I had never thought of iridium doing this though. Thanks @Al Dente

Edited October 18, 2023 by Doctor Mud

[Praefectus]

The North American Atlantic Costal Plain has gone through several stages of transgression and regression. With so many layers in close proximity, it is most likely that any mosasaur specimens found in post-Maastrichtian rocks are reworked. This is especially true when dealing with fossils found in creek and river beds (which most coastal mosasaur remains are) where the specimens are usually disarticulate and found out of context. 

 

"Danian mosasaur" fossils have also been found in Poland. The interpretation of the fossils is that they were reworked there too. 

[pachy-pleuro-whatnot-odon]

On 10/17/2023 at 9:29 PM, FossilDAWG said:

There is good evidence that a few ammonites survived briefly (on the order of hundreds of thousand years at most) into the Danian, the earliest stage of the Paleocene.  For example, rare ammonites are found in the Danian (earliest Paleocene) at Stevns Klint, Denmark.  Other reports of Danian ammonites are more controversial.  Many lines of evidence indicate a rapid change in marine food webs following the terminal Cretaceous event.  It seems not improbable to me that a few ammonites might have initially survived the end of the Cretaceous, but were unable to adapt rapidly enough to long term changes in food availability and other ecosystem changes in the reconfigured post-Cretaceous marine environment.

 

Yeah, we get these Danian survivor ammonites as well, over in the Low Countries - meaning the Netherlands and Belgium. Here are a couple on display at the Maastricht Natural History Museum:

 

 

In a sense, it's easier to believe, I guess, that ammonites would have survived the end-Cretaceous extinction event, because we still have live nautilids with us today. At the same time, as many of the ammonites species were adapted to certain ecological niches and habitats, they would've been more vulnerable to the environmental changes and ecological collapse triggered by the asteroid impact - including changes to the chemistry of the sea water they lived in, probably primarily acidification caused by carbon-dioxide run-off. As has been postulated for the extinction of ichthyosaurs at the end of the Cenomanian, being too highly specialised was probably a major disadvantage to survival.

 

On 10/17/2023 at 9:29 PM, FossilDAWG said:

I am not aware of compelling evidence for survival of large marine reptilian predators beyond the end of the Cretaceous.  They would likely have been even more sensitive than ammonites to changes in food availability.

 

In addition to the above, we should certainly not forget that the higher the trophic level of a species, the more it is at risk when the food web collapses. So, in a sense, if anything, one would expect the more generalist species to survive, as well as those of smaller body size, as this would require less energy in a world of nutrient scarcity.

 

As @Mart1980 will be able to tell you, mosasaur remains are also found in the Middle Danian deposits at Ciply in Belgium (see here), which, however, are also interpreted as being reworked material. I'm not aware of any Mesozoic marine reptile remains having had their primary disposition in Paleocene strata.

[Joseph Fossil]

22 hours ago, pachy-pleuro-whatnot-odon said:

 

Yeah, we get these Danian survivor ammonites as well, over in the Low Countries - meaning the Netherlands and Belgium. Here are a couple on display at the Maastricht Natural History Museum:

 

 

In a sense, it's easier to believe, I guess, that ammonites would have survived the end-Cretaceous extinction event, because we still have live nautilids with us today. At the same time, as many of the ammonites species were adapted to certain ecological niches and habitats, they would've been more vulnerable to the environmental changes and ecological collapse triggered by the asteroid impact - including changes to the chemistry of the sea water they lived in, probably primarily acidification caused by carbon-dioxide run-off. As has been postulated for the extinction of ichthyosaurs at the end of the Cenomanian, being too highly specialised was probably a major disadvantage to survival.

 

 

In addition to the above, we should certainly not forget that the higher the trophic level of a species, the more it is at risk when the food web collapses. So, in a sense, if anything, one would expect the more generalist species to survive, as well as those of smaller body size, as this would require less energy in a world of nutrient scarcity.

 

As @Mart1980 will be able to tell you, mosasaur remains are also found in the Middle Danian deposits at Ciply in Belgium (see here), which, however, are also interpreted as being reworked material. I'm not aware of any Mesozoic marine reptile remains having had their primary disposition in Paleocene strata.

 

@pachy-pleuro-whatnot-odon You made some pretty awesome points dude! I wasn't aware before of the Mosasaur fossils from Ciply, Belgium. I do still have questions about the age of the Piloplatecarpus fossils from Stevn's Klint, Denmark (I'm wondering if they came from below or above the same strata and the Paleocene ammonite there)?

 

@Praefectus @Doctor Mud What do you guys too think? 

[Joseph Fossil]

On 10/19/2023 at 1:49 PM, Praefectus said:

The North American Atlantic Costal Plain has gone through several stages of transgression and regression. With so many layers in close proximity, it is most likely that any mosasaur specimens found in post-Maastrichtian rocks are reworked. This is especially true when dealing with fossils found in creek and river beds (which most coastal mosasaur remains are) where the specimens are usually disarticulate and found out of context. 

 

"Danian mosasaur" fossils have also been found in Poland. The interpretation of the fossils is that they were reworked there too. 

 

@Praefectus @pachy-pleuro-whatnot-odon Thanks for letting me know. I've heard about the Danian Mosasaur fossils from the Wisła valley area of Central Poland too and I agree with you those seem very likely reworked.

 

I'm wondering what you think of the age of Takatika Grit specimens and if much smaller than usual Maastrichtian mosasur species (like those of the genera Halisaurus and Plioplatecarpus) that were on a much lower trophic level than their larger relatives like Mosasaurus are more likely candidates for dead clade walking during the Danian, Paleocene?

[pachy-pleuro-whatnot-odon]

On 10/21/2023 at 1:48 AM, Joseph Fossil said:

I do still have questions about the age of the Piloplatecarpus fossils from Stevn's Klint, Denmark (I'm wondering if they came from below or above the same strata and the Paleocene ammonite there)?

 

Unfortunately, I'm not familiar with these Danish specimens, so am unable to help you resolve this question. However, maybe @The Amateur Paleontologist knows...

 

On 10/21/2023 at 1:58 AM, Joseph Fossil said:

I'm wondering what you think of the age of Takatika Grit specimens and if much smaller than usual Maastrichtian mosasur species (like those of the genera Halisaurus and Plioplatecarpus) that were on a much lower trophic level than their larger relatives like Mosasaurus are more likely candidates for dead clade walking during the Danian, Paleocene?

 

As I mentioned above, smaller, more generalist species on a lower trophic would stand a better chance to get through the K/Pg-extinction event. This is not to say they did, though, and I'm unaware of any mosasaur finds having been described from firmly established Danian contexts. As to Takatika Grit: unfortunately, this thread is the first time I'm hearing of it, so I can't really help you out with that either. Sorry!

[Joseph Fossil]

2 minutes ago, pachy-pleuro-whatnot-odon said:

 

Unfortunately, I'm not familiar with these Danish specimens, so am unable to help you resolve this question. However, maybe @The Amateur Paleontologist knows...

 

 

As I mentioned above, smaller, more generalist species on a lower trophic would stand a better chance to get through the K/Pg-extinction event. This is not to say they did, though, and I'm unaware of any mosasaur finds having been described from firmly established Danian contexts. As to Takatika Grit: unfortunately, this thread is the first time I'm hearing of it, so I can't really help you out with that either. Sorry!

 

@pachy-pleuro-whatnot-odon Thanks for the input bro! I really do appreciate it!!

[Psittacosaur9]

On 10/18/2023 at 5:48 AM, Al Dente said:

 

The Cretaceous/Paleocene boundary is now defined by the iridium layer. The problem with this is iridium may migrate up or down the sediments over time. An ammonite that was deposited beneath the iridium layer in the Cretaceous may now be considered Paleocene because the iridium at that particular site has migrated downward, therefore the Cretaceous/Paleocene boundary has migrated downward at that site.

Just out of interest, how would iridium migrate through sedimentary rock?

[Lone Hunter]

Think it has something to do with iridium being attracted to iron and attaches to it, it will move towards iron deposits the main one being the core of the earth where most of the iridium ended up. How it physically moves on a molecular level have no idea but would think tectonic shifting of land has something to do with it. Betting someone can explain it better than that.

Edited October 27, 2023 by Lone Hunter

[Doctor Mud]

1 hour ago, Psittacosaur9 said:

Just out of interest, how would iridium migrate through sedimentary rock?

I wondered that at first, but remember these rocks could have been soft sediment for thousands of years before they were lithified. I think about the ocean drilling program where they drill through soft sediments that are hundreds of thousands of years old. 
 

Heavier elements can migrate downwards in sediment, just due to gravity I think? I’ll look at the paper again. There was a peak in plutonium deposition from nuclear tests around the world in 1963. It has already migrated downwards cm in some lakes, possibly more in the ocean. Imagine how far it could migrate in thousands of years! 

Edited October 27, 2023 by Doctor Mud

[Psittacosaur9]

1 hour ago, Lone Hunter said:

Think it has something to do with iridium being attracted to iron and attaches to it, it will move towards iron deposits the main one being the core of the earth where most of the iridium ended up. How it physically moves on a molecular level have no idea but would think tectonic shifting of land has something to do with it. Betting someone can explain it better than that.

 

7 minutes ago, Doctor Mud said:

I wondered that at first, but remember these rocks could have been soft sediment for thousands of years before they were lithified. I think about the ocean drilling program where they drill through soft sediments that are hundreds of thousands of years old. 
 

Heavier elements can migrate downwards in sediment, just due to gravity I think? I’ll look at the paper again. There was a peak in plutonium deposition from nuclear tests around the world in 1963. It has already migrated downwards cm in some lakes, possibly more in the ocean. Imagine how far it could migrate in thousands of years! 

Oh wow, thanks for the explanation! I never realised that could happen, but it makes sense.

[Al Dente]

1 hour ago, Psittacosaur9 said:

Just out of interest, how would iridium migrate through sedimentary rock?

 

Fluids in the sediment under reducing conditions.

[Psittacosaur9]

2 minutes ago, Al Dente said:

 

Fluids in the sediment under reducing conditions.

Thanks for sending this to me; it looks interesting! I'll read the paper tomorrow, as I'm about to go to bed.

[hemipristis]

On 10/18/2023 at 11:25 AM, Joseph Fossil said:

 

@Al Dente Also, do you know anyone on the fourm that has gone fossil hunting at the Hornerstown Formation?

I have, in Sewell, NJ. It is exposed in both the marl pit (now a fossil park) and Mantua Creek

[hemipristis]

On 10/27/2023 at 8:26 PM, Doctor Mud said:

I wondered that at first, but remember these rocks could have been soft sediment for thousands of years before they were lithified. I think about the ocean drilling program where they drill through soft sediments that are hundreds of thousands of years old. 
 

Heavier elements can migrate downwards in sediment, just due to gravity I think? I’ll look at the paper again. There was a peak in plutonium deposition from nuclear tests around the world in 1963. It has already migrated downwards cm in some lakes, possibly more in the ocean. Imagine how far it could migrate in thousands of years! 

There are unconsolidated sediments in the millions of years.

 

The migration I believe is geochemical, based upon electrostatic forces