Huffington Department of Earth Sciences

Both body fossil and ichnofossil evidence for gregarious behavior in sauropod dinosaurs is examined. Some localities suggest that herds were partitioned on the basis of age, whereas other sites reveal groups consisting of both adult and juvenile/subadult individuals. Two skeletal accumulations showing evidence of age segregation are examined in detail. The Mother's Day Quarry in the Upper Jurassic Morrison Formation of Montana contains the remains of several immature diplodocoid sauropods. An assemblage in the Upper Cretaceous Javelina Formation of Big Bend National Park in Texas consists entirely of juvenile Alamosaurus. Both the Mother's Day and Big Bend assemblages are interpreted here as remnants of age-segregated herds. The differences between skeletal accumulations composed entirely of immature animals and mixed-age ichnological assemblages imply that herd composition was variable. When age segregation is recognized, in both fossil and modern taxa, it is thought to minimize the fitness costs related to behavioral synchronization within social groups. Age segregation of herds also contraindicates extended parental care as typical of at least some sauropod taxa.

A new formation, the Ketavik Formation, is proposed for Paleogene rocks of Katmai National Park near Brooks Camp. The type section is in an area previously mapped as the Jurassic Talkeetna Formation. The proposed formation was deposited in a fluvial environment. It is distinct from the coeval Copper Lake Formation on the southeast side of the Alaska Peninsula volcanic arc

Two partial theropod braincases recovered from the Upper Cretaceous Prince Creek Formation confirm the presence of Troodon formosus in Alaska. Characters that distinguish one specimen as Troodon formosus include; a very strongly developed sagittal crest on fused parietals, ...

Recent biomechanical evidence has fuelled debate surrounding the winter habits of the hadrosaurian dinosaur Edmontosaurus (ca. 70 Ma). Using histological characteristics recorded in bone, we show that polar Edmontosaurus endured the long winter night. In contrast, the bone microstructure of temperate Edmontosaurus is inconsistent with a perennially harsh environment. Differences in the bone microstructure of polar and temperate Edmontosaurus consequently dispute the hypothesis that polar populations were migratory. The overwintering signal preserved in the microstructure of polar Edmontosaurus bone offers significant insight into the life history of dinosaurs within the Late Cretaceous Arctic.

The Late Cretaceous (Campanian-Maastrichtian) Prince Creek Formation is the most dinosaur-rich high latitude formation in the world, but there is little detailed work that integrates paleontological sites with sedimentology, paleopedology and palynology. Facies ...

FLAIG, Peter P. 1, HASIOTIS, ST 2, VAN DER KOLK, Dolores A. 1, and FIORILLO, Anthony 3,(1) Bureau of Economic Geology, University of Texas at Austin, Jackson School of Geosciences, 10100 Burnet Rd, Austin, TX 78758, peter. flaig@ beg. utexas. edu,(2) ...

ABSTRACT The Cretaceous (Early Maastrichtian), dinosaur-bearing Prince Creek Formation (Fm.) exposed along the Colville River in northern Alaska records high-latitude, alluvial sedimentation and soil formation on a low-gradient, muddy coastal plain during a greenhouse phase in Earth history. We combine sedimentology, paleopedology, palynology, and paleontology in order to reconstruct detailed local paleoenvironments of an ancient Arctic coastal plain. The Prince Creek Fm. contains quartz-and chert-rich sandstone and mudstone-filled trunk and distributary channels and floodplains composed of organic-rich siltstone and mudstone, carbonaceous shale, coal, and ash-fall deposits. Compound and cumulative, weakly developed soils formed on levees, point bars, crevasse splays, and along the margins of floodplain lakes, ponds, and swamps. Abundant organic matter, carbonaceous root traces, Fe-oxide depletion coatings, and zoned peds (soil aggregates with an outermost Fe-depleted zone, darker-colored Fe-rich matrix, and lighter-colored Fe-poor center) indicate periodic waterlogging, anoxia, and gleying, consistent with a high water table. In contrast, Fe-oxide mottles, ferruginous and manganiferous segregations, bioturbation, and rare illuvial clay coatings indicate recurring oxidation and periodic drying of some soils. Trampling of sediments by dinosaurs is common. A marine influence on pedogenesis in distal coastal plain settings is indicated by jarosite mottles and halos surrounding rhizoliths and the presence of pyrite and secondary gypsum. Floodplains were dynamic, and soil-forming processes were repeatedly interrupted by alluviation, resulting in weakly developed soils similar to modern aquic subgroups of Entisols and Inceptisols and, in more distal locations, potential acid sulfate soils. Biota, including peridinioid dinocysts, brackish and freshwater algae, fungal hyphae, fern and moss spores, projectates, age-diagnostic Wodehouseia edmontonicola, hinterland bisaccate pollen, and pollen from lowland trees, shrubs, and herbs record a diverse flora and indicate an Early Maastrichtian age for all sediments in the study area. The assemblage also demonstrates that although all sediments are Early Maastrichtian, strata become progressively younger from south to north. A paleoenvironmental reconstruction integrating pedogenic processes and biota indicates that polar woodlands with an angiosperm understory and dinosaurs flourished on this ancient Arctic coastal plain that was influenced by seasonally(?) fluctuating water table levels and floods. In contrast to modern polar environments, there is no evidence for periglacial conditions on the Cretaceous Arctic coastal plain, and both higher temperatures and an intensified hydrological cycle existed, although the polar light regime was similar to that of the present. In the absence of evidence of cryogenic processes in paleosols, it would be very difficult to determine a high-latitude setting for paleosol formation without independent evidence for paleolatitude. Consequently, paleosols formed at high latitudes under greenhouse conditions, in the absence of ground ice, are not likely to have unique pedogenic signatures.