Preprints
Search for Brennan (9 results)
Pleistocene shifts in Great Basin hydroclimate seasonality govern the formation of lithium-rich paleolake deposits
Published: 2024-04-10
Subjects: Earth Sciences, Hydrology, Oceanography and Atmospheric Sciences and Meteorology, Paleobiology, Sedimentology
Southwestern North America is currently experiencing a multidecadal megadrought, with severe consequences for water resources. However, significant uncertainty remains about how precipitation will change in the 21st century in this semi-arid region. Paleoclimatic records are essential for both contextualizing current change, and for helping constrain the sensitivity of regional hydroclimate to [...]
California margin temperatures modulate regional circulation and extreme summer precipitation in the desert Southwest
Published: 2023-06-01
Subjects: Earth Sciences, Environmental Sciences, Oceanography and Atmospheric Sciences and Meteorology
In August 2022, Death Valley, the driest place in North America, experienced record flooding from summertime rainfall associated with the North American monsoon (NAM). Given the socioeconomic cost of these type of events, there is a dire need to understand their drivers and future statistics. Existing theory predicts that increases in the intensity of precipitation is a robust response to [...]
Broadband Ocean Bottom Seismometer Noise Properties
Published: 2022-05-13
Subjects: Geophysics and Seismology
We present a new compilation and analysis of broadband ocean bottom seismometer noise properties from 15 years of seismic deployments. We compile a comprehensive dataset of representative four-component (seismometer and pressure gauge) noise spectra and cross-spectral properties (coherence, phase, and admittance) for 551 unique stations spanning 18 US-led experiments. This is matched with a [...]
Early Pliocene Marine Transgression into the Lower Colorado River Valley, Southwestern USA, by Re-Flooding of a Former Tidal Strait
Published: 2021-09-29
Subjects: Earth Sciences, Physical Sciences and Mathematics, Sedimentology, Stratigraphy, Tectonics and Structure
Marine straits and seaways are known to host a wide range of sedimentary processes and products, but the role of marine connections in the development of large river systems remains little studied. This study explores a hypothesis that shallow marine waters flooded the lower Colorado River valley at ~ 5 Ma along a fault-controlled former tidal straight, soon after the river was first integrated [...]
Timing of Martian Core Formation from Models of Hf–W Evolution Coupled with N-body Simulations
Published: 2021-06-04
Subjects: Geochemistry, Mineral Physics, Planetary Sciences
Determining how and when Mars formed has been a long-standing challenge for planetary scientists. The size and orbit of Mars are difficult to reproduce in classical simulations of planetary accretion, and this has inspired models of inner solar system evolution that are tuned to produce Mars-like planets. However, such models are not always coupled to geochemical constraints. Analyses of Martian [...]
Mixed carbonate-siliciclastic tidal sedimentation in the Miocene to Pliocene Bouse Formation, palaeo-Gulf of California
Published: 2020-12-09
Subjects: Earth Sciences
Mixed carbonate-siliciclastic deposits provide unique insights into hydrodynamic processes that control sedimentation in tidal systems. This study presents sedimentologic an¬¬d ichnologic data from the upper Miocene¬ to lower Pliocene Bouse Formation, which accumulated during regional transgression at the margin of a tidal strait near the north end of the ancestral Gulf of California. The basal [...]
High-Pressure Deformation of Iron–Nickel–Silicon Alloys and Implications for Earth’s Inner Core
Published: 2020-10-21
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics
Earth’s inner core exhibits strong seismic anisotropy, often attributed to the alignment of hexagonal close-packed iron (hcp-Fe) alloy crystallites with the Earth’s poles. How this alignment developed depends on material properties of the alloy and is important to our understanding of the core’s crystallization history and active geodynamical forcing. Previous studies suggested that hcp-Fe is [...]
Core Formation and Geophysical Properties of Mars
Published: 2019-02-25
Subjects: Earth Sciences, Geochemistry, Mineral Physics, Physical Sciences and Mathematics, Planetary Geophysics and Seismology, Planetary Sciences
The chemical and physical properties of the interiors of terrestrial planets are largely determined during their formation and differentiation. Modeling a planet’s formation provides important insights into the properties of its core and mantle, and conversely, knowledge of those properties may constrain formational narratives. Here, we present a multi-stage model of Martian core formation in [...]
Punctuated Sediment Discharge During Early Pliocene Birth of the Colorado River: Evidence from Regional Stratigraphy, Sedimentology, and Paleontology
Published: 2017-11-14
Subjects: Earth Sciences, Physical Sciences and Mathematics, Stratigraphy
The Colorado River in the southwestern U.S. provides an excellent natural laboratory for studying the origins of a continent-scale river system, because deposits that formed prior to and during river initiation are well exposed in the lower river valley and nearby basinal sink. This paper presents a synthesis of regional stratigraphy, sedimentology, and micropaleontology from the southern Bouse [...]