New U-Pb ages for detrital and igneous zircons constrain the depositional age and sedimentary provenance of the Beardmore Group, a siliciclastic succession that records transformation of the East Antarctic margin during Rodinia breakup and subsequent Gondwana amalgamation. We divide rocks previously mapped as the Beardmore Group into (1) an inboard late Neoproterozoic assemblage (probably ≤670 ...

A rich body of empirically grounded theory has developed about food webs--the networks of feeding relationships among species within habitats. However, detailed food-web data and analyses are lacking for ancient ecosystems, largely because of the low resolution of taxa coupled with uncertain and incomplete information about feeding interactions. These impediments appear insurmountable for most ...

Preservation of soft-bodied organisms is exceedingly rare in the fossil record. One way that such fossils are preserved is as carbonaceous compressions in fined-grained marine sedimentary rocks. These deposits of exceptional preservation are known as Burgess Shale-type (BST) deposits. During the Cambrian Period, BST deposits are more common and provide a crucial view of early animal evolution. ...

Abstract New occurrences of flask-shaped and envelope-bearing microfossils, including the predominantly Cambrian taxon Granomarginata , are reported from new localities, as well earlier in time (Ediacaran) than previously known. The stratigraphic range extends into System, where it had a cosmopolitan distribution. This newly Ediacaran record includes areas Norway (Baltica), Newfoundland (Avalon...

The Great Basin of the western United States has proven important for studies of Proterozoic and Paleozoic geology [2500 to 245 million years ago (Ma)] and has been central to the development of ideas about the mechanics of crustal shortening and extension. An understanding of the deformational history of this region during Mesozoic and Cenozoic time (245 Ma to the present) is required for pali...

The recent proliferation of stratigraphic studies of delta 13C variation in carbonates and organic C in later Neoproterozoic and basal Cambrian successions (approximately 850-530 Ma) indicates a strong oscillating trend in the C-isotopic composition of surface seawater. Alone, this trend does not adequately characterize discrete intervals in Neoproterozoic time. However, integrated with the vec...

For an arbitrary finite Coxeter group W , we define the family of Cambrian lattices for W as quotients of the weak order on W with respect to certain lattice congruences. We associate to each Cambrian lattice a complete fan, which we conjecture is the normal fan of a polytope combinatorially isomorphic to the generalized associahedron for W . In types A and B, we obtain, by means of a fiber-pol...