Floristics of Difficult Creek Natural Area Preserve: a Piedmont mafic woodland complex in Halifax County, Virginia, U.S.A.

The 331-hectare (819-acre) Difficult Creek Natural Area Preserve (DCNAP) was established in Halifax County, Virginia to protect and manage habitat for rare vascu-lar plant species and animals, and to restore plant communities. Mafic metavolcanic rocks of the Virgilina Formation and felsic metavolcanic and metasedimentary rocks of the Aaron Formation comprise the geologic units on the preserve. The Virgilina-derived soils have high shrink-swell potential, a dense hardpan layer, relatively high base status, and a significant gravelly or stony component; these soil conditions support the highest density of rare plant species known on the preserve. The first noteworthy vascular plant species were documented from the property in 1972 by botanist Alton Harvill of Longwood University, but detailed investigations of the flora did not begin until the site was revisited by the second author in 1993. Rare plant inventory has been the primary focus of botanists since that time. In 2001, the property was acquired by the Virginia Department of Conservation and Recreation, Division of Natural Heritage (DCR) and dedicated as a state Natural Area Preserve, at which point active management for natural communities and associated rare species was initiated. Since the rare plants on site thrive in open woodland or savanna-like conditions, prescribed burns and timber harvests have been used by DCR stewards to restore habitat after decades of fire suppression and conversion of hardwood stands to loblolly pine plantations. In 2018, a thorough floristic study was initiated to highlight the significance of this flora beyond the documentation of rare plants. The two-year inventory documented 653 plant taxa, comprising 326 genera in 106 families. Fourteen of these species are of conservation concern at the global or state level; an additional 12 taxa are considered uncommon and of potential conservation concern (Townsend 2019). These rare or uncommon species are components of two globally rare plant communities. In addition, the globally rare lepidopteran, Erynnis martialis (Mottled Duskywing), occurs on the preserve, the only extant population known in Virginia. Due to agricultural impacts and widespread fire exclusion, few analogs to this flora exist within the southern Piedmont of Virginia.

A high-resolution multi-proxy record of late Cenozoic environment change from central Taklimakan Desert, China

The Taklimakan Desert in the Tarim Basin is the largest desert in Central Asia, and is regarded as one of the main dust sources to the Northern Hemisphere. Late Cenozoic sedimentary sequences with intercalated in-situ aeolian dune sands in this area preserve direct evidence for the Asian desertification. Herein, we report a high-resolution multi-proxy climatic record from the precise magnetostratigraphic dated Hongbaishan section in the central Taklimakan Desert. Our results show that a fundamental climate change, characterised by significant cooling, enhanced aridity, and intensified atmospheric circulation, occurred at 2.8 Ma. Good correlations between paleo-environmental records in the dust sources and downwind areas suggest a broadly consistent climate evolution of northwestern China during the late Cenozoic, which is probably driven by the uplift of the Tibet Plateau and the Northern Hemisphere glaciation.

A high-resolution multi-proxy record of late Cenozoic environment change from central Taklimakan Desert, China

The Taklimakan Desert in the Tarim Basin is the largest desert in Central Asia, and is regarded as one of the main dust sources to the Northern Hemisphere. Late Cenozoic sedimentary sequences with intercalated in-situ aeolian dune sands in this area preserve direct evidence for the Asian desertification. Herein, we report a high-resolution multi-proxy climatic record from the precise magnetostratigraphic dated Hongbaishan section in the central Taklimakan Desert. Our results show that a fundamental climate change, characterized by significant cooling, enhanced aridity, and intensified atmospheric circulation, occurred at 2.8 Ma. Good correlations between climate records in the dust sources and downwind areas suggest a broadly consistent climate evolution of northwestern China during the late Cenozoic, which is probably driven by the uplift of the Tibet Plateau and the Northern Hemisphere glaciation.

Evidence for seamount accretion to a peri-Laurentian arc during closure of Iapetus 1This article is one of a series of papers published in CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology.2 Geological Survey of Canada Contribution 20100465.

The Red Indian Line is the fundamental Iapetus suture zone in the Newfoundland Appalchians along which the main tract of the Iapetus Ocean was consumed. Despite being the site of the closure of a wide ocean, few vestiges of the Iapetus plate have been accreted along Red Indian Line. Ordovician rocks in the Notre Dame Bay area preserve the only evidence for accretion of a seamount in Newfoundland. The seamount is characterized by alkali basalt and hypabyssal rocks that are juxtaposed with Darriwilian peri-Laurentian volcanic arc rocks (466 ± 4 and 467 ± 4 Ma) along a major mylonite zone. The mylonite zone lacks sedimentary rocks suggesting that the seamount was accreted to the arc along a sediment-starved interface and that significant subduction erosion took place along the Laurentian margin. Identification of subduction erosion indicates that an accretionary prism did not exist outboard of Laurentia in Newfoundland, in contrast to the well developed accretionary prisms of the Caledonides.