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"Ward, Peter D"
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Mercury evidence from southern Pangea terrestrial sections for end-Permian global volcanic effects
The latest Permian mass extinction (LPME) was triggered by magmatism of the Siberian Traps Large Igneous Province (STLIP), which left an extensive record of sedimentary Hg anomalies at Northern Hemisphere and tropical sites. Here, we present Hg records from terrestrial sites in southern Pangea, nearly antipodal to contemporaneous STLIP activity, providing insights into the global distribution of volcanogenic Hg during this event and its environmental processing. These profiles (two from Karoo Basin, South Africa; two from Sydney Basin, Australia) exhibit significant Hg enrichments within the uppermost Permian extinction interval as well as positive Δ
199
Hg excursions (to ~0.3‰), providing evidence of long-distance atmospheric transfer of volcanogenic Hg. These results demonstrate the far-reaching effects of the Siberian Traps as well as refine stratigraphic placement of the LPME interval in the Karoo Basin at a temporal resolution of ~10
5
years based on global isochronism of volcanogenic Hg anomalies.
Mercury (Hg) concentrations and isotopes from terrestrial sections of southern Pangea provide evidence of the global volcanic effects of the Siberian Traps during the Permian-Triassic transition
Journal Article
A new history of life : the radical new discoveries about the origins and evolution of life on earth
\"The history of life on Earth is, in some form or another, known to us all--or so we think. [This book] offers a provocative new account, based on the latest scientific research, of how modern lifeforms evolved\"--Amazon.com.
Book
Increased Growth and Germination Success in Plants following Hydrogen Sulfide Administration
This study presents a novel way of enhancing plant growth through the use of a non-petroleum based product. We report here that exposing either roots or seeds of multicellular plants to extremely low concentrations of dissolved hydrogen sulfide at any stage of life causes statistically significant increases in biomass including higher fruit yield. Individual cells in treated plants were smaller (~13%) than those of controls. Germination success and seedling size increased in, bean, corn, wheat, and pea seeds while time to germination decreases. These findings indicated an important role of H2S as a signaling molecule that can increase the growth rate of all species yet tested. The increased crop yields reported here has the potential to effect the world's agricultural output.
Journal Article
تاريخ جديد للحياة : الاكتشافات الجديدة الجذرية حول أصول الحياة على الأرض وتطورها
ما زالت نظريات تشارلز داروين، المنشورة أول مرة قبل أكثر من قرن ونصف، تمثل النموذج الإرشادي لكيفية فهم تطور الحياة-لكن التطورات العلمية الأخيرة غيرت ذلك. ينطلق اليوم عالمان بارزان من حصيلة سنوات من البحث في البيولوجيا والكيمياء وعلم الفلك البيولوجي وعلم المستحاثات لتقديم حكاية فيها تبصرة مقتبسة من أفكار ونتائج بحثية جديدة. كل ذلك كتب بأسلوب مرح ومفعم بالحوية والوضوح، مبينا بأن الكثير من اعتقاداتنا الراسخة عن تاريخ الحياة خاطئة.
BOOK
Cephalopod body size and macroecology through deep time
As actively swimming predators, cephalopods have played a key role regulating and engineering marine ecosystems for more than 500 million years and continue to do so. For the first time, we portray fluctuations of cephalopod body size including species from the Cambrian to today. For comparability, we determined the maximum body volumes of each species using various proxies, because classical measures like mantle length cannot be applied homologously to all groups. We separately examined Cephalopoda with orthoconic conchs (without ammonoids and coleoids), Nautilida, Ammonoida (without heteromorphs), and Neocoleoida (squids, octopuses and their ancestors). The long-term trajectories of these groups differ in their overall trends. Each of these groups reacted in other ways to the mass extinctions. All groups except the nautilids evolved species exceeding one meter in size, which belong to the marine megafauna. Nautilids and orthocones share a threshold volume of about 100 litres, while in ammonoids and neocoleoids, the limit lies closer to 500 litres.
Journal Article
Completing the loop of the Late Jurassic–Early Cretaceous true polar wander event
The reorientation of Earth through rotation of its solid shell relative to its spin axis is known as True polar wander (TPW). It is well-documented at present, but the occurrence of TPW in the geologic past remains controversial. This is especially so for Late Jurassic TPW, where the veracity and dynamics of a particularly large shift remain debated. Here, we report three palaeomagnetic poles at 153, 147, and 141 million years (Myr) ago from the North China craton that document an ~ 12° southward shift in palaeolatitude from 155–147 Myr ago (~1.5° Myr
−1
), immediately followed by an ~ 10° northward displacement between 147–141 Myr ago (~1.6° Myr
−1
). Our data support a large round-trip TPW oscillation in the past 200 Myr and we suggest that the shifting back-and-forth of the continents may contribute to the biota evolution in East Asia and the global Jurassic–Cretaceous extinction and endemism.
The authors report three palaeomagnetic poles from the North China craton and document a large round-trip true polar wander oscillation during 155−141 Ma that may have affected biotic evolution in East Asia and global extinction and endemism.
Journal Article
Comparative habits and habitat in extant and extinct nautiloid cephalopods from acoustic telemetry and stable oxygen isotope analyses
Information about behavior and habitat depths of
Nautilus
and
Allonautilus
species, the last remaining nautiloid cephalopod genera, is relevant both to paleobiologists trying to interpret the lives of extinct chambered cephalopods as well as to ecologists seeking to better understand the food webs of the Mesophotic Zone (200–800 m), fore-reef slope communities of the tropical Indopacific where these archaic animals live. One long-standing question is whether the extant nautiloid species live in deeper water than the many extinct species; a second is whether there are habitation depth differences of adult nautiloids compared to juveniles - either now or in the past. Using shell-mounted acoustic transmitters on seven different species in the two extant genera, and oxygen isotope shell thermometry on these same species as well as from fossils of 18 extinct fossil nautiloid species, we found regular, diurnal migration in only one species of each extant genus. Mature individuals in all tracked species of both genera were found to inhabit significantly shallower (and warmer) depths (~ 200 m) than the immature nautiluses and allonautiluses of the same populations (~ 350–400 m). Extinct nautiloid genera showed significantly warmer shell growth temperatures, with the single exception of Eocene through Miocene-aged species of the ammonoid-like genus
Aturia
, although diagenesis from not only ancient, but modern carbonates cannot be ruled out.
Journal Article
Vertical Distribution and Migration Patterns of Nautilus pompilius
Vertical depth migrations into shallower waters at night by the chambered cephalopod Nautilus were first hypothesized early in the early 20(th) Century. Subsequent studies have supported the hypothesis that Nautilus spend daytime hours at depth and only ascend to around 200 m at night. Here we challenge this idea of a universal Nautilus behavior. Ultrasonic telemetry techniques were employed to track eleven specimens of Nautilus pompilius for variable times ranging from one to 78 days at Osprey Reef, Coral Sea, Australia. To supplement these observations, six remotely operated vehicle (ROV) dives were conducted at the same location to provide 29 hours of observations from 100 to 800 meter depths which sighted an additional 48 individuals, including five juveniles, all deeper than 489 m. The resulting data suggest virtually continuous, nightly movement between depths of 130 to 700 m, with daytime behavior split between either virtual stasis in the relatively shallow 160-225 m depths or active foraging in depths between 489 to 700 m. The findings also extend the known habitable depth range of Nautilus to 700 m, demonstrate juvenile distribution within the same habitat as adults and document daytime feeding behavior. These data support a hypothesis that, contrary to previously observed diurnal patterns of shallower at night than day, more complex vertical movement patterns may exist in at least this, and perhaps all other Nautilus populations. These are most likely dictated by optimal feeding substrate, avoidance of daytime visual predators, requirements for resting periods at 200 m to regain neutral buoyancy, upper temperature limits of around 25°C and implosion depths of 800 m. The slope, terrain and biological community of the various geographically separated Nautilus populations may provide different permutations and combinations of the above factors resulting in preferred vertical movement strategies most suited for each population.
Journal Article
Hypoxia, Global Warming, and Terrestrial Late Permian Extinctions
A catastrophic extinction occurred at the end of the Permian Period. However, baseline extinction rates appear to have been elevated even before the final catastrophe, suggesting sustained environmental degradation. For terrestrial vertebrates during the Late Permian, the combination of a drop in atmospheric oxygen plus climate warming would have induced hypoxic stress and consequently compressed altitudinal ranges to near sea level. Our simulations suggest that the magnitude of altitudinal compression would have forced extinctions by reducing habitat diversity, fragmenting and isolating populations, and inducing a species-area effect. It also might have delayed ecosystem recovery after the mass extinction.
Journal Article