Physical Sciences and Mathematics Commons^™

Climate Change And Late Pliocene Acceleration Of Erosion In The Himalaya, Katharine Huntington, Ann Blythe, Kip Hodges

Ann Blythe

Studies of active mountain ranges suggest that atmospheric and geodynamic processes may be strongly coupled through erosion — a hypothesis that has led to a debate over the relative importance of climate and far-field tectonic forcing in influencing erosion. We addressed this debate by developing the detailed long-term erosional history of a transect in the central Annapurna Range of Nepal for comparison with the climate and tectonic forcing histories of the region. Patterns of apatite fission-track and muscovite 40Ar/39Ar apparent ages with elevation indicate a five-fold increase in apparent erosion rate between 2.5 and 0.9 Ma ago. The time frame …

The Karst Of West-Central Florida, Lee J. Florea

Lee J Florea, PhD, P.G.

Caves, the cornerstone feature of karst aquifers, are little understood in Florida. This dissertation, which analyzes the morphology, elevation, lithologic setting, and hydrology of caves in west-central Florida, demonstrates that the karst of the unconfined Floridan aquifer differs from the paradigm view of karst presented in modern geology textbooks. The differences reflect setting: eogenetic (west-central Florida) vs. telogenetic (conventional).

Architecture Of Air-Filled Caves Within The Karst Of The Brooksville Ridge, West-Central Florida, Lee J. Florea

Lee J Florea, PhD, P.G.

Air-filled caves surveyed in the Brooksville Ridge of west-central Florida provide insight into the organization of karstic permeability within the unconfined portions of the Upper Floridan Aquifer. The morphology of the passages that compose these caves in geologically young, high-permeability limestones is strikingly different from caves found in ancient carbonates far from the influence of the coast. Cave passages in west-central Florida are laterally extensive and tiered. Principal horizons of cave development occur between +3 m and +5 m, +12 m and +15 m, and +20 m and +22 m above modern sea level. The primary guide of cave passage …

Morphologic Features Of Conduits And Aquifer Response In The Unconfined Floridan Aquifer System, West Central Florida, Lee J. Florea, H L. Vacher

Lee J Florea, PhD, P.G.

Conduits within the unconfined Floridan Aquifer of west-central Florida include both horizontal and vertical components. In this paper, we investigate each and propose theories based upon cave survey data and a collection of over 300 Florida cave maps. First, we find that vertical portions of conduits visually correlate to fractures, and these fractures tend to be the dominant control of conduit directionality. Length-weighted rose diagrams of passage directions reveal a NW-SE and NE-SW pattern of conduit directions statistically similar to results found in remote sensing studies of photolinears. Secondly we note that horizontal elements of conduits occur at consistent horizons …

Le Voragini Catastrofiche Della Florida, Lee J. Florea, Robert Brooks, Tom Turner, Mario Parise

Lee J Florea, PhD, P.G.

The West-Central Florida landscape is worlds away from white-sand beaches and palm trees: gentle rolling hills, dense jungle-like forests, pine tree and palmetto scrub lands, impenetrable cypress swamps, and alligator-laden rivers. Numerous crystal-clear springs offer a glimpse of the hidden world below these wildly-diverse ecosystems. Internationally recognized in the cave diving community, Florida harbors some of the longest and most spectacular underwater cave systems. Lesser known are Florida’s “dry” caves, that rarely have large natural openings and, though often smaller than their aquatic counterparts, the beauty found within can rival the world’s best show-caves. Little was known about caves and …

Community Education In Karst At The Geological Alumni Society Geopark, University Of South Florida, Beth Fratesi, Lee J. Florea

Lee J Florea, PhD, P.G.

No abstract provided.

Cave Levels, Marine Terraces, Paleoshorelines, And The Water Table In Peninsular Florida, Lee J. Florea, H L. Vacher

Lee J Florea, PhD, P.G.

Levels of passages are a common feature of many cave systems around the world. Likewise, coastal and marine terraces are common in coastal plain settings. This paper extends the discussion of cave levels from traditional research sites in the interior lowlands of the United States to the Atlantic Coastal Plains, namely peninsular Florida. Are there levels in Florida caves, and is there a link between the elevation of cave levels, marine terraces, paleoshorelines, and thus the water table, above and below present sea level in peninsular Florida?

Refine Slip Rates And Segmentation Of The Northern Sangre De Cristo Fault, Colorado’S Largest Active Fault, James P. Mccalpin

James P. McCalpin

We excavated a 25 m-long trench on the northern part of the Crestone section of the Northern Sangre de Cristo fault zone, to see whether the Crestone section might be composed of more than one (independent) rupture segments. The Carr Gulch trench exposed evidence for 3 paleoearthquake displacements in the past 27.4 ka. The existence of 3 colluvial deposits (units 2, 3, 4) indicates that the ca. 4.5 m of surface offset was formed during 3 surface-faulting events with an average displacement of about 1.5 m each. The events occurred at about 8 ka, 20 ka, and between 22.5 and …

Climatic Forcing Of Erosion, Landscape, And Tectonics In The Bhutan Himalayas, Djordje Grujic, Isabelle Coutand, Bodo Bookhagen, Stéphane Bonnet, Ann Blythe, Chris Duncan

Ann Blythe

A fundamental objective in studies of climate-erosion-tectonics coupling is to document convincing correlation between observable indicators of these processes on the scale of a mountain range. The eastern Himalayas are a unique range to quantify the contribution of tectonics and climate to long-term erosion rates, because uniform and steady tectonics have persisted for several million years, while monsoonal precipitation patterns have varied in space and time. Specifically, the rise of the Shillong plateau, the only orographic barrier in the Himalayan foreland, has reduced the mean annual precipitation downwind in the eastern Bhutan Himalaya at the Miocene-Pliocene transition. Apatite fission-track (AFT) …

Evidence For Monazite Growth At ~1.6 Ga And ~1.4 Ga In Proterozoic Migmatites Of The Santa Fe Range, North-Central New Mexico, Dan Heuer, Christopher Daniel

Dan Heuer

Supracrustal Proterozoic migmatites exposed in the Aspen Basin area of the Santa Fe Range represent the northernmost exposure of the Mazatzal (~1.65 Ga) crustal province. Two migmatite samples (plag-bt-ms-qtz-hem±grt) yield preliminary in-situ electron microprobe U-Th-total Pb ages from monazite that are ~1.4 Ga; however, 1 grain yields a core age of ~1.6 Ga.

Monazite are generally aligned subparallel to a regional moderately, south-dipping foliation (S1), indicating monazite growth was pre- or synkinematic. X-ray mapping of monazite shows variable U, Th, Pb, Y, and Ce zoning, interpreted to reflect three periods of monazite growth. Xenotime are relatively unzoned in most elements, …

Monazite Thermochronometry In Migmatites From North-Central New Mexico: Contact Metamorphism Or A Regional Mid-Crustal Melt-Rich Layer?, Dan Heuer, Christopher Daniel, Joseph Pyle

Dan Heuer

Monazite thermochronometry demonstrates that Proterozoic migmatites exposed in the central Santa Fe range and the Rincon range of north-central New Mexico preserve high-temperature monazite that crystallized near 1.4 Ga. No 1.4 Ga plutons are exposed in the Rincon range; however, undated plutons are present in the Santa Fe Range and a contact metamorphic setting is possible. Alternatively, partial melting in these two areas may represent a regional, mid-crustal, melt-rich layer.

Subhedral monazite in both areas are commonly aligned subparallel with the dominant regional foliation. Monazite from the central Santa Fe range show three distinct compositional domains. Relatively high-Y cores yield …

Evidence For A Normal P-T Gradient And Top-North Displacement In The Central Bhutan Himalaya: Shear Sense And P-T Estimates From The Chekha Fm. And The Greater Himalayan Sequence, Dan Heuer, John Witmer, Adam Kahler, M. Ryan Delaney, Adam Dennis, Djordje Grugic, Christopher Daniel

Dan Heuer

Upper amphibolite facies metasedimentary rocks at the base of the Chekha Fm overlie the partially melted Greater Himalaya Sequence (GHS) and likely correlate with the Everest Series in the Mt. Everest massif. From the base of the Chekha Fm, metamorphic grade decreases to slates and unmetamorphosed rocks of the Tethyan sedimentary series (TSS) with increasing elevation. The Chekha Fm is separated from both the GHS and the overlying TSS by normal-sense shear zones related to the south Tibetan Detachment zone (STDZ).

Five samples from near the base of the Chekha Fm are characterized by the mineral assemblage Grt-Bt-St. Garnet crystals …

Formation And Maintenance Of Shear Zones, Caleb Holyoke, Jan Tullis

Caleb Holyoke

No abstract provided.

Mechanisms Of Weak Phase Interconnection And The Effects Of Phase Strength Contrast On Fabric Development, Caleb Holyoke, Jan Tullis

Caleb Holyoke

No abstract provided.

The Interaction Between Reaction And Deformation: An Experimental Study Using A Biotite + Plagioclase + Quartz Gneiss, Caleb Holyoke, Jan Tullis

Caleb Holyoke

No abstract provided.