Phanerozoic Paleotemperatures: The Earth’s Changing Climate during the Last 540 million years

The lower plate is the dominant agent in modern convergent margins characterized by active subduction, as negatively buoyant oceanic lithosphere sinks into the asthenosphere under its own weight. This is a strong plate-driving force because the slab-pull force is transmitted through the stiff sub-oceanic lithospheric mantle. As geological and geochemical data seem inconsistent with the existence of modern-style ridges and arcs in the Archaean, a periodically-destabilized stagnant-lid crust system is proposed instead. Stagnant-lid intervals may correspond to periods of layered mantle convection where efficient cooling was restricted to the upper mantle, perturbing Earth's heat generation/loss balance, eventually triggering mantle overturns. Archaean basalts were derived from fertile mantle in overturn upwelling zones (OUZOs), which were larger and longer-lived than post-Archaean plumes. Early cratons/continents probably formed above OUZOs as large volumes of basalt and komatiite were delivered for protracted periods, allowing basal crustal cannibalism, garnetiferous crustal restite delamination, and coupled development of continental crust and sub-continental lithospheric mantle. Periodic mixing and rehomogenization during overturns retarded development of isotopically depleted MORB (mid-ocean ridge basalt) mantle. Only after the start of true subduction did sequestration of subducted slabs at the core-mantle boundary lead to the development of the depleted MORB mantle source. During Archaean mantle overturns, pre-existing continents located above OUZOs would be strongly reworked; whereas OUZO-distal continents would drift in response to mantle currents. The leading edge of drifting Archaean continents would be convergent margins characterized by terrane accretion, imbrication, subcretion and anatexis of unsubductable oceanic lithosphere. As Earth cooled and the background oceanic lithosphere became denser and stiffer, there would be an increasing probability that oceanic crustal segments could founder in an organized way, producing a gradual evolution of pre-subduction convergent margins into modern-style active subduction systems around 2.5 Ga. Plate tectonics today is constituted of: (1) a continental drift system that started in the Early Archaean, driven by deep mantle currents pressing against the Archaean-age sub-continental lithospheric mantle keels that underlie Archaean cratons; (2) a subduction-driven system that started near the end of the Archaean.

Stagnant lids and mantle overturns: Implications for Archaean tectonics, magmagenesis, crustal growth, mantle evolution, and the start of plate tectonics

Triassic climates — State of the art and perspectives

Long-term cycles of Triassic climate change: a new δ18O record from conodont apatite

Major climate changes and mass extinctions are associated with carbon isotope anomalies in the atmosphere-ocean system and have been shown to coincide with the onset of large igneous provinces (LIPs) and, by association, their emissions of greenhouse gases and aerosols. However, climatic and biological consequences of some known LIP eruptions have not yet been explored. During the Carnian (Late Triassic) large volumes of flood basalts were erupted to form the so-called Wrangellia LIP (western North America). This huge volcanic province is similar in age to a major climatic and biotic change, the Carnian Pluvial Event (CPE), but no evidence of a causal relationship exists other than timing. Here we report a sharp negative δ 13 C excursion at the onset of the CPE recorded in organic matter. An abrupt carbon isotope excursion of ∼−4‰ occurs in terrestrial and marine fossil molecules, whereas total organic carbon records an ∼−2‰ shift. We propose that this carbon isotope negative shift was caused by an injection of light carbon into the atmosphere-ocean system linked to the eruption of Wrangellia flood basalts. This carbon-cycle perturbation occurs slightly before two major evolutionary innovations: the origin of dinosaurs and calcareous nannoplankton.

Discovery of a major negative δ13C spike in the Carnian (Late Triassic) linked to the eruption of Wrangellia flood basalts

The accreted Wrangellia flood basalts and associated sedimentary rocks that compose the prevolcanic and postvolcanic stratigraphy provide an unparalleled view of the architecture, eruptive environment, and accumulation and subsidence history of an oceanic plateau. This Triassic large igneous province extends for ∼2300 km in the Pacific Northwest of North America, from central Alaska and western Yukon (Nikolai Formation) to Vancouver Island (Karmutsen Formation), and contains exposures of submarine and subaerial volcanic rocks representing composite stratigraphic thicknesses of 3.5–6 km. Here we provide a model for the construction of the Wrangellia oceanic plateau using the following information and visualization tools: (1) stratigraphic summaries for different areas of Wrangellia; (2) new 40Ar/39Ar geochronology results; (3) compilation and assessment of geochronology and biostratigraphy for Wrangellia; (4) compiled digital geologic maps; (5) an online photographic archive of field relationships; and (6) a Google Earth file showing the mapped extent of Wrangellia flood basalts and linked field photographs.

Based on combined radiometric (U-Pb, 40Ar/39Ar, K-Ar), paleontological, and magnetostratigraphic age constraints, the Wrangellia flood basalts were emplaced during a single phase of tholeiitic volcanism ca. 230–225 Ma, and possibly within as few as 2 Myr, onto preexisting submerged arc crust. There are distinct differences in volcanic stratigraphy and basement composition between Northern and Southern Wrangellia. On Vancouver Island, ∼6 km of high-Ti basalts, with minor amounts of picrites, record an emergent sequence of pillow basalt, pillow breccia and hyaloclastite, and subaerial flows that overlie Devonian–Mississippian (ca. 380–355 Ma) island arc rocks and Mississippian–Permian marine sedimentary strata. In contrast, Alaska and Yukon contain 1–3.5-km-thick sequences of mostly subaerial high-Ti basalt flows, with low-Ti basalt and submarine pillow basalts in the lowest parts of the stratigraphy, that overlie Pennsylvanian–Permian (312–280 Ma) volcanic and sedimentary rocks. Subsidence of the entire plateau occurred during and after volcanism, based on late-stage interflow sedimentary lenses in the upper stratigraphic levels and the presence of hundreds of meters to >1000 m of overlying marine sedimentary rocks, predominantly limestone. The main factors that controlled the resulting volcanic architecture of the Wrangellia oceanic plateau include high effusion rates and the formation of extensive compound flow fields from low-viscosity, high-temperature tholeiitic basalts, sill-dominated feeder systems, limited repose time between flows (absence of weathering, erosion, sedimentation), submarine versus subaerial emplacement, and relative water depth (e.g., pillow basalt–volcaniclastic transition).

/pdf/the-architecture-of-oceanic-plateaus-revealed-by-the-2zuflinv76.pdf

The architecture of oceanic plateaus revealed by the volcanic stratigraphy of the accreted Wrangellia oceanic plateau

Geochemistry of Triassic flood basalts from the Yukon (Canada) segment of the accreted Wrangellia oceanic plateau

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Steve Israel

Author Tools

Chat about Author

Papers

The architecture of oceanic plateaus revealed by the volcanic stratigraphy of the accreted Wrangellia oceanic plateau

Geochemistry of Triassic flood basalts from the Yukon (Canada) segment of the accreted Wrangellia oceanic plateau