The White Stone Band of the Kimmeridge Clay Formation, an integrated high resolution approach to understanding environmental change

The Kimmeridge Clay is a Jurassic mudrock succession that shows Milankovitch Band climatic cyclicity. A key issue is to determine how the subtle changes that define this cyclicity result from climatic change. Using material from the Natural Environment Research Council Rapid Global Geological Events (RGGE) Kimmeridge Drilling Project boreholes, the White Stone Band was investigated at the lamination scale using backscattered electron imagery and quantitative palynofacies. Fabric analysis shows the lamination to represent successive deposition of coccolith-rich and organic-matter-rich layers. Individual laminae contain unsorted palynological debris with a consistent ratio of marine and terrestrial components. Such mixed organic matter input is interpreted as the result of storm transport. Linking water column processes to laminae deposition suggests seasonal input with a coccolith bloom followed by a more diverse assemblage including dinoflagellates and photosynthetic chlorobiacean bacteria. As the photic zone extended into the euxinic water column organic matter export to the sea bed underwent minimal cycling through oxidation and subsequently became preserved through sulphurization with greatly increased sequestration of carbon. This was significantlyincreased by late season storm-driven mixing of euxinic water into the photic zone. Increased frequency ofstorm systems would therefore dilute the coccolith input to give an oil shale. Hence climatically induced changes in storm frequency would progressively vary the organic content of the sediment and generate the climate cycle signal. Keywords: Milankovitch theory, Kimmeridge Clay, organic matter, high-resolution methods, climate change

Effects of shoot tipping on development and yield of the tuber crop Plectranthus edulis

Plectranthus edulis (Vatke) Agnew is one of the tuber crops of the genus Plectranthus that is widely cultivated in Africa and Asia. P. edulis produces below-ground tubers on stolons originating from the stems, comparable to the potato (Solanum tuberosum L.). Farmers apply several laborious cultural practices to enhance shoot growth and yield, among which shoot tipping is very common. Tipping (pinching) is the removal of the shoot apex with one or two pairs of leaves from the main stems and branches. The rationale of this practice, especially when repeated more than once during one cropping season, is not fully understood. One similar experiment with two cultivars was carried out at two locations (Awassa and Wondogenet) in Ethiopia to assess and analyse the effects of shoot tipping and its frequency on crop development and tuber production. Tipping treatments included zero tipping, tipping once, tipping twice and tipping thrice, with the first tipping taking place 68 days after planting (DAP), a stage at which most of the stems reached a height of about 0·15 m, and the remainder following at intervals of 44–46 days. Tipping stimulated stem branching; it significantly increased the number of primary, secondary and tertiary stems in both experiments. Soil cover increased with an increase in the frequency of the tipping in Awassa, because of the tipping effects on the different canopy development variables. Tipping also enhanced the soil cover in Wondogenet, but the crop did not gain any extra benefit from a third tipping. Tipping enhanced early stolon formation, but did not consistently affect the number of stolons per hole later in the growing season. The number of tubers increased with an increase in the frequency of tipping in both cultivars in Wondogenet and in one cultivar in Awassa. Tuber dry matter yield increased with an increase in the frequency of tipping at both sites. Fresh tuber yield in the final harvest at 208 DAP was c. 1·9 kg/m2. Tipping on average increased fresh tuber yield by 17% in Wondogenet, whereas the difference was not detectable in Awassa. Because senescence was delayed slightly by tipping, yield effects of tipping might be larger when harvesting later. In general, there was a positive effect of tipping on canopy development and tuber yield

Mid-Devonian Archaeopteris roots signal revolutionary change in earliest fossil forests

The origin of trees and forests in the Mid Devonian (393–383 Ma) was a turning point in Earth history, marking permanent changes to terrestrial ecology, geochemical cycles, atmospheric CO2 levels, and climate. However, how all these factors interrelate remains largely unknown. From a fossil soil (palaeosol) in the Catskill region near Cairo NY, USA, we report evidence of the oldest forest (mid Givetian) yet identified worldwide. Similar to the famous site at Gilboa, NY, we find treefern-like Eospermatopteris (Cladoxylopsida). However, the environment at Cairo appears to have been periodically drier. Along with a single enigmatic root system potentially belonging to a very early rhizomorphic lycopsid, we see spectacularly extensive root systems here assigned to the lignophyte group containing the genus Archaeopteris. This group appears pivotal to the subsequent evolutionary history of forests due to possession of multiple advanced features and likely relationship to subsequently dominant seed plants. Here we show that Archaeopteris had a highly advanced root system essentially comparable to modern seed plants. This suggests a unique ecological role for the group involving greatly expanded energy and resource utilization, with consequent influence on global processes much greater than expected from tree size or rooting depth alone

Rebuilding terrestrial ecosystems after the end-Devonian mass extinction: insights from the TW:eed Project

The TW:eed (Tetrapod World: early evolution and diversification) project is a major research initiative that will generate a coherent picture of the biotic, environmental and geological conditions of the 15-20 million years recovery period following the major extinction event at the end-Devonian that was a major turning point in terrestrial evolution. A paucity of terrestrial invertebrates and few fossils of early tetrapods have been found in post-Devonian successions from the immediate aftermath (Romer’s Gap) and yet, during a relatively brief time period in the Early Carboniferous, fully terrestrial vertebrates evolved, terrestrial arthropods radiated, ray-finned fishes took over from lobe-finned forms and plant groups diversified. Several new localities in Carboniferous successions in southern Scotland and northern England are providing completely new insights into this pivotal period for the evolution of life on land. Significant new tetrapod material is helping to populate Romer’s Gap. Localities are also yielding a diverse fauna of fish (gyracanthids, lungfish, rhizodonts and actinopterygians), invertebrates (malacostracans, eurypterids, ostracods, scorpions and myriapods) and plants. The fossil localities are within the Ballagan Formation, a distinctive unit comprising mudstones with interbedded sandstones, palaeosols and thin beds of dolomitic “cementstone”. The sediments were deposited on an extensive low relief, muddy, vegetated floodplain that was traversed by numerous river systems. Periodically the river-derived floods submerged the floodplains generating extensive shallow freshwater lakes. The presence of gypsum and anhydrite indicates that there were occasional marine transgressions across a marginal coastal plain. So far, most of the fossils have been found towards the top of the Ballagan Formation, but a coastal exposure of the entire formation provides a unique opportunity to search for fossils across a time interval of about 15 million years at the base of the Carboniferous. In addition to the detailed analysis of key outcrops, a drilling program in the Tweed Basin is in the process of acquiring 500 m of continuous core through these earliest Carboniferous successions. A tight stratigraphic framework for tetrapod localities across the region will be generated by integrating the sedimentological (lithostratigraphy), micropalaeontological (biostratigraphy), chemostratigraphical (carbon and oxygen stable isotopes) and petrophysical data from the core and outcrops. The borehole will provide the high-resolution datasets required to investigate the local, and potentially, global palaeoclimate and its evolution through this time interval. This multifaceted project is a unique opportunity to examine the progression, causes and context of the rebuilding of an ecosystem following a major extinction

Lycopsid forests in the early Late Devonian paleoequatorial zone of Svalbard

The Middle to early Late Devonian transition from diminutive plants to the first forests is a key episode in terrestrialization. The two major plant groups currently recognized in such “transitional forests” are pseudosporochnaleans (small to medium trees showing some morphological similarity to living tree ferns and palms) and archaeopteridaleans (trees with woody trunks and leafy branches probably related to living conifers). Here we report a new type of “transitional” in-situ Devonian forest based on lycopsid fossils from the Plantekløfta Formation, Munindalen, Svalbard. Previously regarded as very latest Devonian (latest Famennian, 360 Ma), their age, based on palynology, is early Frasnian (ca. 380 Ma). In-situ trees are represented by internal casts of arborescent lycopsids with cormose bases and small ribbon-like roots occurring in dense stands spaced ?15–20 cm apart, here identified as Protolepidodendropsis pulchra Høeg. This plant also occurs as compression fossils throughout most of the late Givetian–early Frasnian Mimerdalen Subgroup. The lycopsids grew in wet soils in a localized, rapidly subsiding, short-lived basin. Importantly, this new type of Middle to early Late Devonian forest is paleoequatorial and hence tropical. This high-tree-density tropical vegetation may have promoted rapid weathering of soils, and hence enhanced carbon dioxide drawdown, when compared with other contemporary and more high-latitude forests

Palynological calibration of Devonian events at near-polar palaeolatitudes in the Falkland Islands, South Atlantic

In the Devonian, the Falkland Islands were part of the high-latitude Cape Basin. West Falkland palynological assemblages are at a low thermal maturity level but also very low in diversity and dominated by simple spores with rare chitinozoans and acritarchs. The South Harbour Member contains rare verrucate and sculptured trilete spores, and is early Lochkovian. The Fish Creek Member palynofloras are late Lochkovian. The best correlative datum is the transgressive Fox Bay Formation where the palynological assemblage includes Ramochitina magnifica and is equivalent to the Sequence B transgression in Brazil (dated as late Pragian–earliest Emsian). The early Eifelian upper Fox Bay Formation spore assemblage is comparable to the Sequence C transgression in Brazil and the ?Chote? Event. The facies and position of the base Port Philomel Formation prasinophyte-rich black shale suggests the late Eifelian transgression (Ka?ák Event). Above this level is the inception of Geminospora lemurata (base Givetian). The upper Port Stanley Formation contains a late (but not latest) Famennian assemblage. Comparisons with both South Africa and South America indicate a number of correlative transgressive and regressive events that match to Euramerica. These correlations are at a continental scale and confirm eustatic control of these Devonian events

Tentaculitids in palynological preparations: New evidence from the Famennian (Late Devonian) of Southern Timan

This is the first report of organic tentaculitid remains (zoomorphs) in palynological preparations of Famennian Age (Southern Timan, borehole Sosnovka-1). Earlier two similar finds have been described from the Frasnian of Poland as similar to embryonic and juvenile forms of dacryoconarids belonging to the orders Nowakiida and Stylionida