The oxidative weathering of organic matter and its carbon dioxide emissions: Insight from the trace elements rhenium and molybdenum

Throughout geological history, the exposure of sedimentary rocks to chemical weathering at Earth’s surface has profoundly affected the geochemistry of the atmosphere, rivers and oceans. Oxidative weathering reactions can release redox-sensitive trace elements, and the concentration and isotope composition of these elements in geological materials may provide an insight into the environmental conditions and processes occurring both today and over Earth’s history. To constrain how Earth’s geological carbon cycle operates, and the influence it has on global climate change, a better understanding of the controls on oxidative weathering is required. The oxidation of organic carbon in sedimentary rocks (petrogenic organic carbon, OCpetro) releases carbon dioxide (CO2) from long-term storage in the lithosphere, and consumes atmospheric O2. Alongside volcanism, the oxidative weathering of OCpetro is the main source of CO2 to the atmosphere over millions of years. However, OCpetro oxidation is poorly understood, both in terms of the rate at which it releases CO2 and the factors that interact to drive the reaction. Trace metals associated with organic matter in rocks, such as rhenium (Re) and molybdenum (Mo), can be released to the dissolved load of rivers during oxidative weathering. Quantifying these element fluxes has the potential, therefore, to provide insight into the oxidative weathering processes involved. Here, rates of OCpetro oxidation rates are quantified in rapidly eroding mountain river catchments in the western Southern Alps, New Zealand, and the Mackenzie River Basin, north west Canada. Physical erosion is found to be a first order control on the oxidative weathering fluxes, but catchments dominated by valley glaciers and exposed to frost-shattering processes experience a further two to three times elevation in CO2 emissions relative to catchments with less glacial cover. The oxidative weathering processes are also found to fractionate metal isotopes (e.g. Mo) in the Critical Zone, which places an important control on the Mo isotope composition of both continental runoff and the World’s oceans

Sedimentary record of Early Permian deglaciation in southern Gondwana from the Falkland Islands

The deglaciation of southern Gondwana during the Early Permian was preceded by waxing and waning of the south polar ice sheet. The fluctuations in ice extent are recorded in the sedimentary record by strata separating thick deposits of glacial diamictite from post-glacial mudrock. These deposits span across all of the major Gondwana fragments, now recognized as South Africa, South America, India, Antarctica and Australia, and also occur on the Falklands and Ellsworth Mountains microplates created during break-up of the supercontinent in the Mesozoic. We present sedimentary evidence for the progression of deglaciation from the Falkland Islands microplate using a series of borehole core runs acquired during onshore mineral exploration. Glacial advance and retreat phases are inferred from the Hells Kitchen Member of the Port Sussex Formation; the rock succession that conformably overlies the main body of glacial diamictite known locally as the Fitzroy Tillite Formation. The pulsated nature of the transition to fully post-glacial conditions was accompanied by an intricate interplay of sedimentary processes, including soft sediment deformation, meltwater pulses and turbidity currents. The Falkland Islands core data lend insight into the evolving Early Permian environment and offer an unusually complete view of continental margin deglaciation preserved in the ancient sedimentary record. Supplementary material: Borehole core photographs from the Fitzroy Tillite Formation, Hells Kitchen Member and Black Rock Member for cores DD029 and DD090 are available at https://doi.org/10.6084/m9.figshare.c.4031119.v

Early Permian climate change in the Falkland Islands

An Early Permian glacial diamictite forms a distinctive unit within the Falkland Islands sedimentary succession and two aspects of its significance have recently been serendipitously enhanced. Fossil discoveries in exotic limestone clasts bear on palaeogeography, whilst a series of mineral-exploration borehole cores have allowed a detailed study of the sedimentary record of deglaciation that followed deposition of the diamictite. Statistical analysis of reflectance and XRF core-scanning data has identified likely Milankovitch periodicities and enabled tentative time-scale modelling. The ‘icehouse to greenhouse’ transition appears to have spanned approximately 1.2 million years, with waning cycles of re-advance superimposed on overall glacial retreat. The new results play into a long-debated geological paradox: although the Falkland Islands are now proximal to the South Atlantic coastline of South America, their geology bears an uncanny resemblance to that of the Cape Fold Belt and Karoo Basin in South Africa. This puzzled the geological pioneers, but became readily explicable when first continental drift and then plate tectonics were invoked to reconstruct the break-up of the Gondwana supercontinent—although the details remain controversial. One of the key stratigraphical correlation levels throughout the major fragments of southern Gondwana—South Africa, South America, Antarctica and Australia—is the glacigenic deposit left behind by the extensive, Late Carboniferous to Early Permian regional glaciation; in the Falkland Islands it is designated the Fitzroy Tillite Formation

The Grizzly, October 6, 2022

Remembering Adam Walton \u2725 • Fall 2022 Editorial Staff • Meet Dr. Rebecca Lyczak and Her Research Team • Get Your Life in Shape With Laura Cunningham • Opinions: First-Year Athlete Check-in • Men\u27s and Women\u27s Tennis Back on Their Home Courts! • Mary Lauren Franz Scores Two Goals Against WAC! • New Health Hub Coming Soon! • Upcoming Gameshttps://digitalcommons.ursinus.edu/grizzlynews/1996/thumbnail.jp

The Grizzly, October 13, 2022

Meet Arthur Artene, Student Government President • Petite Filet in my Wismer? More Likely Than You Think • A Note From the Editor • Dr. Len Lawson, Award-Winning Poet and Scholar • Alex Peay \u2709 and Rising Up • Opinions: Plans for Fall Break Fun • Understanding Stress and Preventing Burnouthttps://digitalcommons.ursinus.edu/grizzlynews/1997/thumbnail.jp

The Grizzly, November 3, 2022

Nuclear Research Gets New Funding • Celebration of Lights • A November Note From the Editor • Calling the Audience to the Stand • Media on Main Markets for Local Businesses • Opinions: I am a Privileged Gay Man, and Yes, I Want You to Care About Abortion Rights! • What do the Phillies Mean to Ursinus? • New Women\u27s Soccer Coach: Killin\u27 It!https://digitalcommons.ursinus.edu/grizzlynews/1999/thumbnail.jp

The Grizzly, February 16, 2023

Spring Rush \u2723 • Ursinus Reacts to an Eagles Loss • The Hunt for a New English Professor • Dominating Diabetes • Meet Amanda Laucks \u2723 • Opinions: What are the Lovers of Ursinus Doing This Valentine\u27s Day? • Spring Sports are Back • Super Bowl Recaphttps://digitalcommons.ursinus.edu/grizzlynews/2005/thumbnail.jp

The Grizzly, April 6, 2023

The Super Bowl of Admissions • Loose Change Takes Center Stage in Lower Wismer • An April Note From the Editor • Following the Trail to Oregon • Humor Writing: Not Just Something to Laugh at • Opinions: What is That Building Called?; What Will You Miss About Ursinus? • 46 Deep: Ursinus Men\u27s LAX Story From a Player\u27s Perspectivehttps://digitalcommons.ursinus.edu/grizzlynews/2011/thumbnail.jp

The Grizzly, October 10, 2024

My Big Fat Greek Cleanup • Bear Necessities Draws Big Brother Concern • Free Speech Lecture by Samantha Harris • A Bit About the B\u27Naturals • IIE Launches Hispanic Heritage Month Celebration • Opinions: How I Learned to Stop Worrying and Love Clamer Hall • Men\u27s Soccer Out to Triumphant Start • Cross Country Gears Up for Strong Finish!https://digitalcommons.ursinus.edu/grizzlynews/2039/thumbnail.jp

The Grizzly, October 26, 2023

A Conversation With Dr. Gundolf Graml • Thinking Locally With UC Votes • Future Developments on Main • A Look Inside Art Club • Film Club Documentary • Opinions: A Divided Ursinus • Ursinus Women\u27s Rugby Team Prepares to Tackle the Season Ahead • UC Field Hockey Doesn\u27t Cut Corners in Victory Over Ranked Swarthmorehttps://digitalcommons.ursinus.edu/grizzlynews/2019/thumbnail.jp