Fossil faeces (coprolites) provide unique trophic perspectives on ancient ecosystems. Yet, although thousands of coprolites have been discovered, specimens that can be unequivocally attributed to carnivorous dinosaurs are almost unknown. A few fossil faeces have been ascribed to herbivorous dinosaurs 1-3 , but it is more difficult to identify coprolites produced by theropods because other carnivorous taxa coexisted with dinosaurs and most faeces are taxonomically ambiguous. Thus sizeable (up to 20 cm long and 10 cm wide) phosphatic coprolites from Belgium 4 and India 5,6 that have been attributed to dinosaurs might have been produced by contemporaneous crocodylians 7 or fish. But there is no ambiguity about the theropod origin of the Cretaceous coprolite we report here. This specimen is more than twice as large as any previously reported carnivore coprolite, and its great size and temporal and geographic context indicate that it was produced by a tyrannosaur, most likely Tyrannosaurus rex. The specimen contains a high proportion (30-50%) of bone fragments, and is rare tangible evidence of theropod diet and digestive processes.The specimen (SMNH P2609.1) was discovered as an elongate mass weathering out of the fluvial Maastrichtian Frenchman Formation in Southwestern Saskatchewan, roughly 35 km southeast of the town of Eastend. The fractured mass was distinguished by its indurated nature and numerous inclusions of comminuted bone. The main portion of the mass was found in situ in a bentonitic mudstone, though numerous fragments had eroded downslope. No fossil bones were found in association with the coprolite, but fossils of a number of large vertebrates have been recovered from the Frenchman Formation 8 .The main body of the specimen is roughly 44 cm long, 13 cm high and 16 cm wide (Fig. 1). The density of the material (approximately 2.94 g ml −1 ) and the weight of all portions (over 7.1 kg) indicate that the present volume of the mass is ϳ2.4 litres, though it is likely that the original faecal mass was larger before it was subjected to compaction, attrition, and/or desiccation. Broken surfaces of the specimen expose numerous dark brown macroscopic bone fragments ranging from 2 to 34 mm in length. These pieces are suspended in a microcrystalline ground mass and are generally aligned in a consistent direction. The ground mass also contains sand-sized bone clasts (Fig. 2). Most of the included bone appears to be similar in type, with highly vascularized cortical bone tissue up to 14-mm thick in a fibrolamellar pattern. All of the observed bone is primary, and no lines of arrested growth were detected.Bulk chemical analyses using X-ray fluorescence (Table 1) reveal marked differences between the specimen and the Frenchman Formation mudstone. The bone-bearing specimen contains high concentrations of phosphorus and calcium, and lower concentrations of aluminium and silicon, relative to the host sediment. Microprobe analyses of specific areas of the specimen indicate that the bone fragments and coprolitic ground mass...
Ash Mountain, South Tuya, and Tuya Butte are three small basaltic volcanoes in the Stikine volcanic belt of northern British Columbia. The volcanoes rise 700, 500, and 400 m above their bases and are about 3.2, 1.6, and 2.6 km3 in volume, respectively. They began eruptive activity under several hundred meters of overlying glacial ice, or water in an ice‐impounded lake, and undegassed pillow lava was erupted and forms the bases of all three. Later, as the vents grew into shallow water, explosive phreatomagmatic activity erupted partly degassed glassy tuffs. Finally, when the volcano emerged through the surface of the ice or water (or the water was drained), degassed subaerial lava flows were erupted and were converted to assemblages of foreset‐bedded pillow breccia and pillow lava when subaerial flows crossed a shoreline and flowed into meltwater lakes. The undegassed subglacial pillow base of Ash Mountain is overlain by partly degassed pillows and hyaloclastite tuff cut by dikes; at South Tuya the pillow base is overlain by hyaloclastite tuffs and lenses of pillow lava; at Tuya Butte the pillow base is overlain by foreset‐bedded pillow lava, pillow breccias, and hyaloclastite tuffs, which in turn are overlain by subaerial lava flows composing a small shield volcano. The undegassed basal subglacial pillow lava of the three volcanoes contain 0.10 ± 0.01 wt % sulfur and ∼0.5 wt % H2O. The overlying partly degassed assemblages contain 0.06 ± 0.02% sulfur and ∼0.2% H2O at Ash Mountain, 0.07±0.01% sulfur at South Tuya, and 0.03±0.01% sulfur at Tuya Butte. The differences in the degree of degassing can be related to the nature of eruption and quenching and the distance of flow of the subaerial lava. When the volcanoes switched from subglacial to shallow water or subaerial eruptions, as shown by change to more explosive activity and then to subaerial lava flows (and by a marked reduction of sulfur in volcanic glass), the magma shifted from tholeiitic to alkalic composition. This transition occurs at each of the three volcanoes. The tholeiitic and alkalic magmas cannot be related by shallow crystal fractionation and apparently originated by differing degrees of deep melting at a mantle source. Prior to eruption the tholeiitic melts overlay alkalic melts in shallow chambers underlying each of the volcanoes because of their lower density and were, therefore, the first to erupt under subglacial conditions. As the volcano grew through the ice (or ice‐impounded water), the volcanic conduit vented to the atmosphere, producing a partial depressurization of the conduit and the subsurface chamber. This sudden reduction in confining pressure caused enhanced vesiculation of volatile saturated melts, particularly of the more volatile‐rich alkalic melts, causing them to rise to the top of the chamber and erupt.
Within the neovolcanic zones of Iceland many volcanoes grew upward through icecaps that have subsequently melted. These steep-walled and flat-topped basaltic subglacial volcanoes, called tuyas, are composed of a lower sequence of subaqueously erupted, pillowed lavas overlain by breccias and hyaloclastites produced by phreatomagmatic explosions in shallow water, capped by a subaerially erupted lava plateau. Glass and whole-rock analyses of samples collected from six tuyas indicate systematic variations in major elements showing that the individual volcanoes are monogenetic, and that commonly the tholeiitic magmas differentiated and became more evolved through the course of the eruption that built the tuya. At Herdubreid, the most extensively studies tuya, the upward change in composition indicates that more than 50 wt.% of the first erupted lavas need crystallize over a range of 60°C to produce the last erupted lavas. The S content of glass commonly decreases upward in the tuyas from an average of about 0.08 wt.% at the base to < 0.02 wt.% in the subaerially erupted lava at the top, and is a measure of the depth of water (or ice) above the eruptive vent. The extensive subsurface crystallization that generates the more evolved, lower-temperature melts during the growth of the tuyas, apparently results from cooling and degassing of magma contained in shallow magma chambers and feeders beneath the volcanoes. Cooling may result from percolation of meltwater down cracks, vaporization, and cycling in a hydrothermal circulation. Degassing occurs when progressively lower pressure eruption (as the volcanic vent grows above the ice/water surface) lowers the volatile vapour pressure of subsurface melt, thus elevating the temperature of the liquidus and hastening liquid-crystal differentiation.
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