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Paleozoic echinoderm hangovers: Waking up in the Triassic

Echinoderms are among the marine invertebrates that underwent the most severe losses at the end-Permian extinction. The prevailing paradigm claims an extreme bottleneck with only very few, if not single, holdovers ("hangovers" herein) sparking the post-Paleozoic radiation. Show More Summary

Microfossil measures of rapid sea-level rise: Timing of response of two microfossil groups to a sudden tidal-flooding experiment in Cascadia

Comparisons of pre-earthquake and post-earthquake microfossils in tidal sequences are accurate means to measure coastal subsidence during past subduction earthquakes, but the amount of subsidence is uncertain, because the response times of fossil taxa to coseismic relative sea-level (RSL) rise are unknown. Show More Summary

Subtropical climate conditions and mangrove growth in Arctic Siberia during the early Eocene

The early Eocene (ca. 56–47.8 Ma) was an interval of exceptional warmth with reduced pole-to-equator temperature gradients. Climate proxies indicate mean annual air temperatures (MATs) and sea-surface temperatures (SSTs) exceeding 8–18...Show More Summary

New age constraints on Aptian evaporites and carbonates from the South Atlantic: Implications for Oceanic Anoxic Event 1a

High-resolution carbon isotope ( 13 C) profiles from shallow- and deep-water carbonates in the South Atlantic (Campos and Santos Basins) are here correlated to stratigraphically well calibrated Tethyan sections, constraining the end of major evaporite deposition in the South Atlantic to the early Aptian Oceanic Anoxic Event (OAE) 1a interval. Show More Summary

Recent retreat of Columbia Glacier, Alaska: Millennial context

Columbia Glacier in Prince William Sound, Alaska, has retreated ~20 km in the past three decades. We use marine sediment records to document the Columbia Glacier advance and retreat history over the past 1.6 k.y. in an effort to place its recent retreat in the context of the Common Era (C.E.). Show More Summary

Paleofluvial and subglacial channel networks beneath Humboldt Glacier, Greenland

The identification of subglacial drainage systems can inform our understanding of past and present hydrological processes, landscape evolution, and ice dynamics. Here, we present evidence from satellite imagery, digital elevation models,...Show More Summary

Shear wave splitting across the Mid-Atlantic region of North America: A fossil anisotropy interpretation

New shear wave splitting measurements (n = 76) from the Mid-Atlantic section of North America, when combined with previously reported measurements, provide improved clarity to patterns of seismic anisotropy across the region, including a rotation of fast polarization directions () from east-west to northeast-southwest in Pennsylvania (USA). Show More Summary

Defining the mechanism for compaction of the CV chondrite parent body

The Allende meteorite, a relatively unaltered member of the CV carbonaceous chondrite group, contains primitive crystallographic textures that can inform our understanding of early Solar System planetary compaction. To test between models...Show More Summary

Recycling of metal-fertilized lower continental crust: Origin of non-arc Au-rich porphyry deposits at cratonic edges

Recent studies argue that subduction-modified, Cu-fertilized lithosphere controls the formation of porphyry Cu deposits in orogenic belts. However, it is unclear if and how this fertilization process operates at cratonic edges, where numerous large non-arc Au-rich deposits form. Show More Summary

Rock magnetic chronostratigraphy of the Shuram carbon isotope excursion: Wonoka Formation, Australia

The Shuram carbon isotope excursion represents a late Precambrian perturbation to Earth’s carbon cycle. Several mechanisms have been proposed, including global ocean oxygenation, methane hydrate release, and diagenesis. The plurality...Show More Summary

Evidence for hydrothermal alteration and source regions for the Kiruna iron oxide-apatite ore (northern Sweden) from zircon Hf and O isotopes

Zircon grains from the Kiruna iron oxide–apatite (IOA) ore bodies in northern Sweden are distinct in their hafnium and oxygen isotopic ratios compared to zircon grains from adjacent metavolcanic host rocks and related intrusions. Here,...Show More Summary

A Micro-Bloom

I pulled off for a pit stop at Bob Scott Summit and started seeing little tiny wildflowers everywhere. I looked around, hoping to see a superbloom, like so many were reporting this year, but the flowers were either somewhat far between, or—where covering the ground—were itsy bitsy. Show More Summary

Pine Valley and Carlin Canyon Squiggles

What is this?!!1?1!? It all started when I was trying to find out what rock formations and rock types I was seeing while making the long trip to work and back out near Elko. Looking around, I found this geologic map (Smith and Ketner,...Show More Summary

Liveblogging the Deluge: The Other Shoe Drops!

2 months agoAcademics / Geology : Geotripper hasn't rained in weeks. Why am I still talking about "liveblogging the deluge"? This is the case of the other shoe dropping. For months we have had storm after storm, adding up to a record year of precipitation in Northern California, and nearly a record in the central state. Show More Summary

Stonehurst Creek

Stonehurst Creek isn’t really a creek, just a stormwater channel. But there it is on the watershed map, with a name and everything. Of the 13 named tributaries that feed San Leandro Creek, it’s the last one before the Bay. And it’s got potential. I only discovered Stonehurst Creek because one day last June I […]

AZGS Stakeholders: Arizona Geological Survey state-allocated funding of $941,000 reinstated

6 May 2017Dear Supporters and Colleagues: On 5 May, 2017, Gov. Ducey signed the FY 2018 budget bill passed the previous day by the Senate and the House. This bill includes funding of $941,000 for AZGS, so as of 1 July we will once again receive state-allocated funds to perform our duties as detailed in state statute. Show More Summary

The Hawai'i That Was: A Geological and Anthropological Exploration of the Islands

2 months agoAcademics / Geology : Geotripper

Since last summer I've been working on a blog series based on the geology, natural history, and anthropology of the Hawaiian Islands, loosely based on our field studies class last summer. There are a lot of stories told by these isolated islands in the middle of the Pacific Ocean. Show More Summary

The Hawai'i That Was: The Final Refuge

3 months agoAcademics / Geology : Geotripper

Kaua'i broke, if not in half, then certainly something close to it. The entire summit of the Kaua'i volcano slipped downward along a fault four million years ago, causing streams to change their direction and causing the erosion of the spectacular gorge of Waimea Canyon. Show More Summary

Mountain View Cemetery: The Bay area’s best landscape

Although I’m tempted just to let the photos in this post stand on their own, let me make a case that Mountain View Cemetery offers the best landscape in the Bay area. First there’s the cemetery itself. The managers have been putting a lot of effort into improving the ground — see the excellent new […]

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