Happy Valentine Formation Day!

With Valentine's Day having come on Friday, I thought it would be fun to show some love to the Valentine Formation. This geologic unit, from the Middle Miocene of Nebraska, is a great fossil producer but not especially famous, so let's give it a moment in the spotlight.

The Valentine Formation comes by its name from Valentine, Nebraska, which in turn was named for post-Civil War Nebraska politician Edward K. Valentine. From there I don't know how many steps it might be to a connection to Saint Valentine, but that's all trivia between friends. If you were reading this a hundred years ago, in 1925, the Valentine Formation would be a newfangled name introduced by Barbour and Cook in 1917. (Barbour and Cook 1917a is usually credited, perhaps because it spends slightly more time on the topic, but the first time "Valentine" was used actually occurred a couple of pages prior in Barbour and Cook 1917b. Neither would be considered formal descriptions today, as you might have gathered from the tone of my description.) Before that, the trail gets tangled quickly. Early fossil descriptions used nothing at all (Leidy 1858) or attributed the strata to the "Loup Fork beds", a name that today produces only blank looks or, if you have some interest in the ever-popular field of historical nomenclature of geologic formations, an image of a time when successful politicians could have facial hair like Edward K. Valentine's. Around the turn of the 20th century the Ogallala Formation came into use (Darton 1898). It had better luck than the Loup Fork beds, indeed persisting to this day as both a formation and a group, but there were improvements to be made. Specifically, people began applying it so broadly that it was in danger of becoming meaningless. Then came the Valentine Formation, which somehow made things worse in the short term. When you start seeing papers with titles like "The Nebraska Geological Survey and the 'Valentine Problem'" (Lugn 1938), something has gone wrong somewhere. Fortunately, Lugn's paper went a long way toward sorting things out. If you're interested in the whole gory history, Skinner and Johnson (1984) is invaluable.

Lower jaw of Pseudaelurus intrepidus, a Valentine Formation cat. Plate I, Figure 8 from Leidy (1869).

With that awkward introduction out of the way, what is the Valentine Formation? Geographically, it is centered on the Niobrara River valley of northern Nebraska. It was deposited during a geologically narrow sliver of time in the Middle Miocene; the Hurburt Ash, erupted about 13.55 million years ago, is found low in the formation just above the Norden Bridge local fauna, and the Swallow Ash from about 12.18 million years ago is found low in the overlying Ash Hollow Formation (Tedford et al. 2004). For those of you who know about North American Land Mammal Ages, it slots into the later Barstovian (Ba2) and the early Clarendonian (Cl1) (Tedford et al. 2004). It is overall a fluvial/floodplain formation, with permanent streams, forests, and savanna woodlands (Diffendal and Voorhies 1994), deposited under a nearly frostless warm temperate to subtropical seasonal climate (MacGinitie 1962).

The Valentine Formation is divided into several members, but don't be necessarily looking for layer cakes. As a fluvial/floodplain setting, cutting and filling was an important process. The members in ascending stratigraphic order (oldest to youngest) are the Cornell Dam, Crookston Bridge, Devil's Gulch, and Burge Members (Skinner and Johnson 1984). The differences can be subtle. The Cornell Dam Member is composed primarily of gray to white sandstone, sand, siltstone, and clay, and is unique among the members for including significant volcanic ash. The Crookston Bridge Member differs mainly in its lack of ash, less clay, and slightly different color (can be buff or yellowish) (Skinner and Johnson 1984). The Devil's Gulch Member is the most distinctive, being composed mainly of yellowish fine sand in a clay matrix, with no bedding features (Skinner et al. 1968). It may have been deposited under a dried climate, with more contribution by wind (Skinner and Johnson 1984). The Burge Member at the top is mostly unconsolidated gray sand with some gravel and clay lenses (Skinner et al. 1968; Skinner and Johnson 1984). Above is the Ash Hollow Formation. The two formations are both part of the Ogallala Group. The Ash Hollow Formation also has a strong fossil record (e.g., Ashfall Fossil Beds), but we're talking about Valentine's Day and not Ash Hollow Day, so it'll have to wait.

Horn of Merycodus warreni, a Valentine Formation pronghorn. Plate XXVII, Figure 12 in Leidy (1869) (as Cervus warreni).

And what kinds of fossils can be found in the Valentine Formation? Pretty much anything that existed in the middle of North America during the Middle Miocene. Leidy (1858) was the first paleontologist to sink his teeth into describing the fossils of the Niobrara River valley, but unfortunately he was working second-hand, with fossils supplied by Ferdinand Vandeveer Hayden, and stratigraphic and location information is pretty minimal. (The Hayden material has mixed stratigraphy, with Leidy describing Pleistocene horses and the "imperial mammoth" as well as various Miocene species. This is hardly unusual, as the Miocene strata in the valley are overlain by Quaternary sediments that also have fossils. Nebraska is a great place to find mammoths, as any visitor to the University of Nebraska's "Elephant Hall" knows.) Inevitably Cope and Marsh took their shots as well, even if there weren't dinosaurs (Marsh 1870, 1874; Cope 1890a, 1890b). They have been followed by many others since then.

One of the greatest fossil sites that seemingly almost no one has heard of is the Norden Bridge Quarry. As noted by Voorhies and Corner (1993), this site has yielded more species of fossil mammals (89 at that time) than any other individual quarry anywhere in the world. It also does not stint on fish, amphibians, or reptiles, bringing it up to more than 140 vertebrate taxa (Voorhies 1990). If you're wondering how, it's a phenomenal microvertebrate site. (So no, it's not exactly the Carnegie Quarry wall.) The most thorough description of the site can be found in Voorhies (1990), which lavishes it with nearly 240 pages of text and illustrations. Regrettably, finding a copy of Voorhies (1990) itself is not the easiest task. Skinner and Johnson (1984) can help with the stratigraphy, and the Paleobiology Database can get you a taxonomic list. When you end up with 140+ taxa, even a summary makes a (very dry) paragraph, so to spare those of you who may not want an otherwise pleasant article spoiled by a roll call of about three dozen mammal families and nearly that many families of other vertebrates, plus explanatory glosses, I will omit it and recommend the link to the rest of you. As the name suggests, it is located near the Norden Bridge over the Niobrara River. It is near the base of the formation, in the Cornell Dam Member, and represents part of an ancient valley. Most bones are disarticulated, broken, and abraded from transportation by rivers (Voorhies 1990). The site was discovered in 1929 and has been worked by several museums, including among others the American Museum of Natural History, the Michigan Museum of Paleontology, the Nebraska State Museum, and the Smithsonian (Skinner and Johnson 1984). More than a dozen fossil species have been named from the site.

Lower jaw of Leptocyon vafer, a Valentine Formation dog. Plate I, Figure 11 in Leidy (1869) (as Canis vafer).

If small vertebrates aren't your thing, maybe you'd prefer large mammals. The Valentine Railway Quarries have more species of large mammals than any other in the Miocene of North America (Voorhies and Corner 1993). With all of the qualifications, this is perhaps not quite as impressive as Norden Bridge, but it's still nothing to sneeze at; North America was not exactly lacking for large mammals during the Miocene. These sites are south of Valentine and adjacent to rail lines (hence the name), and have been worked since the 1910s (Skinner and Johnson 1984). Stratigraphically they are slightly higher, being in the Crookston Bridge Member (Skinner and Johnson 1984). A particular specialty is horses, with 11 or 12 identified at the genus or species level.

Teeth of Parahippus cognitus, a Valentine Formation horse. Plate XXI, Figure 7 in Leidy (1869).

Perhaps your Valentine would not be complete with some flowers? There are certainly plant fossils in the Valentine Formations, including leaves of flowering plants, although not quite the flowers themselves. The most notable plant site in the Valentine Formation is the Kilgore flora, described in MacGinitie (1962). It is also in the Crookston Bridge Member (Skinner and Johnson 1984). The macrofossils of this site include deciduous hardwoods from floodplains and pine-oak woodlands on the highlands between river valleys (MacGinitie 1962), but the pollen indicate non-woody plants were more diverse and the setting was more like the modern East African savanna, or comparable in some ways to the modern Niobrara River valley (Gabel et al. 1998).

If you're interested in getting a look at the Valentine Formation, the Niobrara River within Niobrara National Scenic River cuts through the formation, offering plenty of opportunities to imagine a time when northern Nebraska was populated by gomphotheres, camels, alligators, oreodonts, beardogs, rhinos, and others. Remember to leave any fossils you may come across where you found them!

Lower jaw of Aepycamelus robustus, a Valentine Formation camel. Plate XV, Figure 1 in Leidy (1869) (as Procamelus robustus).

References

Barbour, E. H., and H. J. Cook. 1917a. Skull of Aelurodon platyrhinus, sp. nov. Nebraska Geological Survey 7(19): 173–180.

Barbour, E. H., and H. J. Cook. 1917b. Notes on the skull of Metoreodon. Nebraska Geological Survey 7(18): 165–172.

Cope, E. D. 1890a. On two new species of Mustelidae from the Loup Fork Miocene of Nebraska. American Naturalist 24(2): 950–952.

Cope, E. D. 1890b. On a new dog from the Loup Fork Miocene. American Naturalist 24(2): 1067–1068.

Darton, N. H. 1898. Preliminary report on the geology and water resources of Nebraska west of the one hundred and third meridian. Pages 719–785 in C. D. Walcott. Nineteenth annual report of the United States Geological Survey to the Secretary of the Interior, 1897-1898: Part IV, Hydrography. U.S. Geological Survey Annual Report 19(4).

Diffendal, R. F., Jr., and M. R. Voorhies. 1994. Geologic framework of the Niobrara River drainage basin and adjacent areas in South Dakota generally east of the 100th meridian west longitude and west of the Missouri River. Nebraska Geological Survey, Lincoln, Nebraska. Report of Investigations 9.

Gabel, M. L., D. C. Backlund, and J. Haffner. 1982. The Miocene macroflora of the northern Ogallala Group: northern Nebraska and southern South Dakota. Journal of Paleontology 72(2): 388–397.

Leidy, J. 1858. Notice of remains of extinct Vertebrata, from the valley of the Niobrara River, collected during the exploring expedition of 1857, in Nebraska. Proceedings of the Academy of Natural Sciences of Philadelphia 10:20–29.

Leidy, J. 1869. The extinct mammalian fauna of Dakota and Nebraska: including an account of some allied forms from other localities, together with a synopsis of the mammalian remains of North America. Journal of the Academy of Natural Science of Philadelphia 7: 1–472. (see also here for better plates)

Lugn, A. L. 1938. The Nebraska State Geological Survey and the "Valentine Problem". American Journal of Science (5th series) 36(213): 220–227.

MacGinitie, H. D. 1962. The Kilgore flora: a late Miocene flora from northern Nebraska. University of California Publications in Geological Sciences 35(2): 67–158.

Marsh, O. C. 1870. Notice of some fossil birds from the Cretaceous and Tertiary formations of the United States. American Journal of Science and Arts (2nd series) 49: 205–217.

Marsh, O. C. 1874. Notice of new equine mammals from the Tertiary formation. American Journal of Science (3rd series) 7: 247–258.

Skinner, M. F., and F. W. Johnson. 1984. Tertiary stratigraphy and the Frick Collection of fossil vertebrates from north-central Nebraska. American Museum of Natural History Bulletin 178: 215–368.

Skinner, M. F., S. M. Skinner, and R. J. Gooris. 1968. Cenozoic rocks and faunas of Turtle Butte, south-central South Dakota. American Museum of Natural History Bulletin 138: 379–436.

Tedford, R. H., L. B. Albright III, A. D. Barnosky, I. Ferrusquia-Villafranca, R. M. Hunt Jr., J. E. Storer, C. C. Swisher III, M. R. Voorhies, S. D. Webb, and D. P. Whistler. 2004. Mammalian biochronology of the Arikareean through Hemphillian interval. Pages 169–231 in M. O. Woodburne, editor. Late Cretaceous and Cenozoic mammals of North America. Columbia University Press, New York, New York.

Voorhies, M. R. 1990. Vertebrate paleontology of the proposed Norden Reservoir Area, Brown, Cherry, and Keya Paha Counties, Nebraska. Division of Archeological Research, University of Nebraska, Lincoln, Nebraska. Technical Report 82-09.

Voorhies, M. R., and R. G. Corner. 1993. An inventory and evaluation of vertebrate paleontological sites along the Niobrara/Missouri scenic riverways project corridors. Internal National Park Service report.