ALBERT

Description: 〈span〉Evidence from the fossil coral record has shown that coral assemblages were able to extend their geographical range to higher latitudes during past global warming events. In the face of future global warming scenarios, we investigate the potential for China’s subtropical coral communities to act as a refuge for corals as ocean temperatures continue to warm. Using uranium-thorium dating to chronologically constrain the age of dead corals, we reveal two distinct periods of coral growth between 6.85 and 5.51 ka B.P. and 0.11 to –0.05 ka B.P. (relative to A.D. 1950). The former coincides with the mid–Holocene Warm Period when temperatures in South China were ~1–2 °C warmer than present. Very few ages (13%) were obtained for the ~5.6 k.y. that followed. An increased frequency of corals with 〈sup〉230〈/sup〉Th ages dated to the past century suggests an increase in abundance coinciding with rising global temperatures. Nevertheless, modern monitoring programs have reported a recent dramatic decline in coral cover over the past 34 yr attributable to human influences. Our results suggest that although coral communities existed around the subtropical islands of Daya Bay (southeast China) in the past, their continued presence in the region largely depends on appropriate management of the adjacent coastline and coupled ocean-atmosphere conditions similar to those experienced in the mid-Holocene.〈/span〉

Description: 〈span〉Hillslopes constitute the majority of Earth’s land surface area and dominate the supply of sediment to rivers. Hillslope sediment transport is commonly modeled with a rate law that depends on slope and a rate coefficient, 〈span〉D〈/span〉, that is understood to represent the intensity of transport mechanisms. Although many transport mechanisms are related to water and biota, it is unclear whether 〈span〉D〈/span〉 varies predictably with climate and life. We compiled previous estimates of 〈span〉D〈/span〉 from around the world and also made new estimates for additional sites. The compilation reveals an overall trend in which 〈span〉D〈/span〉 increases strongly with increasing moisture among relatively dry sites and less strongly with increasing moisture among relatively wet sites. Vegetation type has a secondary effect on 〈span〉D〈/span〉 among drier sites, with 〈span〉D〈/span〉 increasing from deserts to grasslands to forests, but not among wetter sites. These trends suggest that the establishment of life in a landscape substantially accelerates soil creep, whereas differences in biological communities among sites with abundant moisture have a relatively small effect on creep.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉Hillslopes constitute the majority of Earth’s land surface area and dominate the supply of sediment to rivers. Hillslope sediment transport is commonly modeled with a rate law that depends on slope and a rate coefficient, 〈span〉D〈/span〉, that is understood to represent the intensity of transport mechanisms. Although many transport mechanisms are related to water and biota, it is unclear whether 〈span〉D〈/span〉 varies predictably with climate and life. We compiled previous estimates of 〈span〉D〈/span〉 from around the world and also made new estimates for additional sites. The compilation reveals an overall trend in which 〈span〉D〈/span〉 increases strongly with increasing moisture among relatively dry sites and less strongly with increasing moisture among relatively wet sites. Vegetation type has a secondary effect on 〈span〉D〈/span〉 among drier sites, with 〈span〉D〈/span〉 increasing from deserts to grasslands to forests, but not among wetter sites. These trends suggest that the establishment of life in a landscape substantially accelerates soil creep, whereas differences in biological communities among sites with abundant moisture have a relatively small effect on creep.〈/span〉

Description: 〈span〉The Paleozoic construction of Pangea advanced southwestward from the Appalachian system to the Marathon fold-and-thrust belt in west Texas and progressively closed a remnant ocean basin between Laurentia and Gondwana. The resulting collisional orogen was a potential driver of Ancestral Rocky Mountain tectonism and impacted continental-scale sediment routing. New detrital zircon U-Pb geochronologic and heavy mineral provenance data from Ordovician−Pennsylvanian strata in the Marathon fold-and-thrust belt, and Permian strata in the Guadalupe Mountains of west Texas record changes in sediment provenance during the tectonic development of southwestern Laurentia and the Delaware Basin. In the Marathon fold-and-thrust belt, Ordovician rocks (Woods Hollow and Marathon Formations) record peri-Gondwanan sediment sources prior to continent collision. Syncollisional Mississippian and Pennsylvanian rocks (Tesnus, Haymond, Gaptank Formations) record contributions from distal Appalachian sources, recycled material from the active continental suture, and volcanic arc material from Gondwana. Near the Guadalupe Mountains, postcollisional Permian strata (Delaware Mountain Group) from the northern Delaware Basin margin suggest a dominantly southern catchment that was sourced from the deforming suture and Gondwanan arc. The results demonstrate that both plates and the active suture zone were sources for the siliciclastic wedge, but their proportions differed through time. These results also suggest that the delay between initial late Mississippian suturing in the Marathon region and increased mid-Permian siliciclastic deposition into the northern Delaware Basin may have been linked to a southward catchment expansion that integrated the collisional belt and southern volcanic arc into a broadly north-directed sediment dispersal system.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉Evidence from the fossil coral record has shown that coral assemblages were able to extend their geographical range to higher latitudes during past global warming events. In the face of future global warming scenarios, we investigate the potential for China’s subtropical coral communities to act as a refuge for corals as ocean temperatures continue to warm. Using uranium-thorium dating to chronologically constrain the age of dead corals, we reveal two distinct periods of coral growth between 6.85 and 5.51 ka B.P. and 0.11 to −0.05 ka B.P. (relative to A.D. 1950). The former coincides with the mid–Holocene Warm Period when temperatures in South China were ∼1–2 °C warmer than present. Very few ages (13%) were obtained for the ∼5.6 k.y. that followed. An increased frequency of corals with 〈sup〉230〈/sup〉Th ages dated to the past century suggests an increase in abundance coinciding with rising global temperatures. Nevertheless, modern monitoring programs have reported a recent dramatic decline in coral cover over the past 34 yr attributable to human influences. Our results suggest that although coral communities existed around the subtropical islands of Daya Bay (southeast China) in the past, their continued presence in the region largely depends on appropriate management of the adjacent coastline and coupled ocean-atmosphere conditions similar to those experienced in the mid-Holocene.〈/span〉