A late Mesoproterozoic detrital zircon (DZ) age population, which was previously considered diagnostic of a link between the Lhasa terrane and northwest Australia, occurs in other Gondwanan components, thus obscuring paleogeographic position Gondwana. Here we compiled large-n (n ≥ 300) DZ U-Pb data from potential source regions various proposed reconstructions, attempted to synthesize spectra t...

Continental siltstones of the Mesoproterozoic Copper Harbor Formation, Michigan contain macroscopic structures of a size and morphological complexity commonly associated with fossils of eukaryotic macroorganisms. A biogenic origin for these structures would significantly augment the Proterozoic continental fossil record, which is currently poor, and also add to a growing body of sedimentologica...

U–Pb zircon geochronology is hampered by problems acquiring meaningful geologic ages on zoned grains that retain isotope signatures from multiple growth or thermal events. We present a new method using laser ablation-multicollector-inductively coupled plasma-mass spectrometry to overcome complications asso­ ciated with intricately zoned zircon crystals through in situ sampling of zircon volumes...

Paleovalleys are components of regional unconformities that provide important constraints on the tectonic evolution of orogenic systems. Some paleovalleys represent canyons cut through deformed strata. Others comprise linear rift-valleys filled with lakes, streams, or alluvium. Locally preserved fluvial and alluvial gravel may directly link source regions to depositional basins, providing timel...