Introducing European Aalenian Ammonites

[Ludwigia]

Good morning.

I already mentioned a few days ago in my member's introduction that I'm interested in Jurassic Fauna, and particularly those Ammonites which range up from the Upper Toarcian through the Aalenian and up into the Lower Bajocian.

I'm also very much interested in the palaeogeographic situation of that era as well as Ammonite migrations and radiations and have studied quite a bit about the European side of things. What I'd like to find out some more about, if any one over there can help me, is what Ammonite families predominated in North America during the period of the Aalenian?

I've googled some helpful literature lately, and have searched this Forum for clues, but there's hardly anything directly to be found about the Aalenian, although there's quite a bit about the Toarcian and the Bajocian in America.

One of the predominant western Tethyan Ammonite families is that of the Graphoceratidae, which probably derived from the Super Family Hildoceratidae and appeared beginning with the species Ludwigia at the bottom of the Murchisonae-Zone. This distinct lineage developed on with the species Brasilia in the Bradfordensis-Zone and Graphoceras in the Concavum-Zone. The family then apparently died out in the lower Bajocian, with the species Hyperlioceras. The Graphoceratidae seemingly originated in the Mediterranian province of the Tethys and radiated from there to many parts of the middle Jurassic world, but I'm still wondering if they made it to America.

Here are some photos of my finds of the major species of this family in the south of Germany in their chronological order of appearance: Ludwigia murchisonae, Brasilia bradfordensis, Graphoceras concavum and Hyperlioceras desori.

[Ludwigia]

Another closely related family is that of the Leioceratinae, beginning with Leioceras opalinum in the upper Toarcian and ending with the species Staufenia in the upper Aalenian. Here's a link to Leioceras opalinum in our German Forum, since I don't have one in my collection.

http://www.steinkern.de/index.php?option=com_zoom&Itemid=41&page=view&catid=96&PageNo=3&key=27&hit=1

And here's a photo of Staufenia staufensis from the Wutach area on the edge of the Black Forest.

[Ludwigia]

The last family I'd like to mention is that of the Hammatoceratidae. This lineage began much earlier than the others back in the early Toarcian and it is generally accepted that they gave birth to the 3 Super Families which dominated up to the end of the Jurassic: Stephanocerataceae, Perisphinctaceae and Haplocerataceae. This Family(or Super Family?) has been a bone of contention amongst the experts ever since Arkell first put the Treatise together. A friend of mine who specializes in identifying Ammonites told me recently: "Ask 2 experts about a Hammatoceras and you'll get 3 different answers"

One thing's for certain anyway, and that is that the family made it to America. I'd love to see some pictures of some of them. Here's one of mine. Up until recently it was called Hammatoceras diadematoides, now it's Breydia with a crown Who knows what I'll have to call it next week

Edited June 9, 2010 by Ludwigia

[Terry Dactyll]

Ludwigia.... Very nice specimens you have found.... I hope someone can help with your request for information....

[Ludwigia]

To finish off my part here, I'd just like to mention a bit about the palaeogeographical situation in those times.

The Supercontinent Pangaea was just breaking up into Gondwana and Laurasia and all the land masses were still pretty close together. The Tethys ocean was however first quite separated from its Pacific counterpart on the west side of North America. First of all a northern passage to the Boreal ocean began to open up which eventually developed into the North Atlantic, and an "Hispanic Corridor", "Caribbean Tethys" or "Atlantic Seaway" has been postulated which opened up somewhat later, running across from Iberia to Mexico.

These widening and deepening corridors, and also the route around South America, allowed for a Faunal radiation from the European Tethys to all parts of the world at that time. The Tethyan Ammonites seem to have used mostly the first two above mentioned routes in order to reach the west coast of North America, leaving some clues of their existence along the way.

Is there anybody here who can show me some of these Aalenian clues which they might have discovered, say in Connecticut, Texas, Oregon, B.C. or the Yukon? Or anywhere else for that matter....

Best wishes, Roger

[Ludwigia]

Oh! Hi Steve! See you've just slipped in between the lines. Nice to see you here. Europe never sleeps, at least at this time of day. I'm going to bed now though. Just got off the night shift.

Best wishes, Roger.

[Shamalama]

Hi Lugwigia,

I belatedly welcome you to the forum and am enjoying this thread that you started. Sadly, I don't find many ammonites near me as I'm in Paleozoic rock. Keep up the good work!

[Fossildude19]

Ludwiga,

Thanks for the interesting and informative post.

You have some great specimens there.

Thanks for sharing your knowledge and fossils with us.

Regards,

[fossil fury]

You're very knowledgeable. Beautiful specimens there too...

[Ludwigia]

Thanks for your nice comments everyone.

I'm still hoping for some knowledgeable Americans to tell me about their finds. Just keeping

[Ludwigia]

Well, it was worth a try....

Just to let you know that if anyone does respond, I'm away for a week now, so don't despair if I don't get back right away

Best wishes, Roger.

[Uncle Siphuncle]

I wish we had some Jurassic to hunt here in TX...as far as I know only the Malone Mountains east of El Paso hold marine exposures of that age. I've seen images of the ammonoids found there and preservation was not very impressive. The Cretaceous however is another story. I wonder how many thousands or more ammonites are taken every year by Texas collectors, everything from pyritized micromorphs up to 300-400 LB steinkerns...

[Plantguy]

Hi Roger,

I personally havent ever run into this age material in my travels...Closest I ever got was years ago I was collecting L.Jurassic Buchiid Pelcypods in California. Before and during that time Ralph Imlay was one individual who was doing research/collecting/publishing professional papers with the USGS that I am aware of--he was one of the ammonite experts. I'm sure you've probably run across his name in your research/readings.

Anyways, here's just a quick list of those papers. I'm not sure if Aalenian ammonites/environments might be mentioned in any of these but I'll list them anyway. I'm sure he probably published in other venues but this is a US Geological Survey Professional Paper listing. Maybe there is a clue to the detail you are looking in one of these docs if you havent already investigated these...some are available for download/viewing.

The publications warehouse at the USGS is at http://pubs.er.usgs.gov/

Good luck in your pursuit/endeavor to learn more about this topic...sounds like you've already done a wealth of research.

Regards, Chris

1984 PP 1322

Early and middle Bajocian (Middle Jurassic) ammonites from southern Alaska

Imlay, R. W.

More Info... Purchase Now 1982 PP 1232

Jurassic (Oxfordian and late Callovian) ammonites from the Western Interior region of the United States

Imlay, R. W.

More Info... Purchase Now 1981 PP 1190

Late Jurassic ammonites from Alaska

Imlay, Ralph William

More Info... Purchase Now 1981 PP 1148

Early Jurassic ammonites from Alaska

Imlay, Ralph Willard

More Info... Purchase Now 1981 PP 1142

Jurassic (Bathonian and Callovian) ammonites in eastern Oregon and western Idaho

Imlay, Ralph Willard

More Info... Purchase Now 1980 PP 1091

Middle Jurassic (Bathonian) ammonites from southern Alaska

Imlay, Ralph Willard

More Info... Purchase Now 1976 PP 854

Middle Jurassic (Bajocian and Bathonian) ammonites from northern Alaska

Imlay, Ralph Willard

More Info... Purchase Now 1975 PP 836

Stratigraphic distribution and zonation of Jurassic (Callovian) ammonites in southern Alaska

Imlay, Ralph Willard

More Info... Purchase Now 1973 PP 756

Middle Jurassic (Bajocian) ammonites from eastern Oregon

Imlay, Ralph Willard

More Info... Purchase Now 1970 PP 643-D

Some Jurassic ammonites from central Saudi Arabia

Imlay, R. W.

More Info... Purchase Now 1968 PP 593-C

Lower Jurassic (Pliensbachian and Toarcian) ammonites from eastern Oregon and California

Imlay, R. W.

More Info... Purchase Now 1972 PP 418

Jurassic ammonites from southern Alaska

Imlay, Ralph W.

More Info... 1961 PP 374-D

Late Jurassic ammonites from the western Sierra Nevada, California

Imlay, Ralph Willard

More Info... Purchase Now 1962 PP 374-C

Jurassic (Bathonian or early Callovian) ammonites from Alaska and Montana

Imlay, Ralph Willard

More Info... Purchase Now 1953 PP 249-B

Callovian (Jurassic) ammonites from the United States and Alaska; Part 2, Alaska Peninsula and Cook Inlet regions

Imlay, R. W.

More Info... 1953 PP 249-A

Callovian (Jurassic) ammonites from the United States and Alaska; Part 1, Western interior United States

Imlay, R. W.

More Info... Purchase Now 1919 PP 118

Some American Jurassic ammonites of the general Quenstedticeras, Cardioceras, and Amoeboceras, family Cardioceratida

[siteseer]

Thanks for your nice comments everyone.

I'm still hoping for some knowledgeable Americans to tell me about their finds. Just keeping

Ludwigia,

I'm a little late on this. There aren't a lot of Jurassic marine exposures in the US because much of it was above sea level during much of the period. I have seen American Jurassic ammonites only from Alaska and those sites are quite remote (accessible only by helicopter). Many other sites that do yield them are not very productive. Two friends and I have been talking about prospecting ammonite sites in California this year. However, many are on private land and are Cretaceous with the owners preferring that strangers stay away. I'm away from home now but I believe an arm of the Pacific reached into Wyoming during the Mid-Late Jurassic (the Sundance Sea). I think mostly vertebrates have been found in the formation.

Plantguy's list is very helpful. I have at least one of Imlay's publications. A few years ago, the USGS had some copies on its "free to a good home" cart.

[Ludwigia]

Well, I've just arrived back from Yorkshire and will tell something about it in another posting later on, but I just wanted to say thanks to Dan and Chris for your helpful and encourageing replies. Particular thanks to Chris for the great list of literature. I've heard of Ralph Imlay, but was not aware of many of the publications which you have mentioned. It seems to be turning out as I suspected, that those particular layers of the upper Aalenian are hardly or not at all accessible over there, but I'll carry on my research. Maybe something will turn up.

Best wishes, Roger.

[insectboy]

Some very nice specimens you have there!

[Plantguy]

Hey Ludwigia,

Was out on the web again...Here's more that maybe you havent already found........

An article from 1988 in Oregon Geology. Middle Jurassic (late Aalenian and early Bajocian)

ammonite biochronology of the Snowshoe Formation, Oregon by David G. Taylor. It had a zonal chart in Figure 3 Correlation of late Aalenian-early Bajocian zonations from the conterminous United States, South Alaska, South America, and Europe. Not sure how current this is but it may help. You can get a pdf copy at their site.

http://www.oregongeology.org/pubs/og/OGv50n11-12.pdf

And here's one other possible source for info....also mentioned in the references cited section of Taylor's article above:

Westermann, G.E.G., 1964, The ammonite fauna of the Kialagvik Formation

at Wide Bay, Alaska Peninsula, Part I, Lower Bajocian (Aalenian):

Bulletins of American Paleontology, v. 47, no. 216, p. 3Z7-503.

Good luck, Regards, Chris

[Ludwigia]

Thanks ever so much, Chris! That's exactly the sort of thing I'm looking for: a comparison of Zones and their Faunal content.

Best wishes, Roger