This guidebook provides detailed itineraries of three of the geological field trips related to the 2017 joint meeting of the GSA Northeastern and North-Central Sections in Pittsburgh. The first chapter outlines a walking trip of downtown Pittsburgh and the escarpment to its south, consisting of seven “Pitt stops” investigating geological, archaeological, and historical aspects of the Gateway to the West. Venturing further afield, the second chapter describes a trip that explores periglacial features as far as the Upper Youghiogheny River basin in Maryland and the Laurel Highlands of Pennsylvania. The third chapter investigates hydrologic aspects of the 1889 Johnstown, Pennsylvania, flood, largely following the progress of the flood from its point of origin to the city of Johnstown.
This volume includes seven field guides that explore the diverse geology of Virginia from its Appalachian highlands to the Atlantic shore. The guides cover an array of topics ranging from cave and karst development in the Valley and Ridge to the exceptional fossil localities at the Carmel Church Quarry and the cliffs near Stratford Hall to Precambrian rocks in the Blue Ridge Mountains. Three guides focus on the Paleozoic to Proterozoic tectonic history of the Blue Ridge and Piedmont provinces, two guides discuss the stratigraphy and fossil assemblages preserved in Cenozoic deposits on the Atlantic Coastal Plain, one guide examines Paleozoic stratigraphy and cave formation in western Virginia, and the final guide explores the relationship between the geology of the Fall Zone and the Civil War during the Petersburg Campaign in 1864–1865.
Johnstown, Pennsylvania, has long been associated with flooding due to major floods in 1889, 1936, and 1977. The most famous of these floods, the Johnstown Flood of 1889, led to more than 2200 deaths and was the result of the catastrophic collapse of the South Fork Dam. This privately owned dam was located on the South Fork of the Little Conemaugh River, ~14 mi (23 km) upstream of Johnstown. The dam changed ownership multiple times since its initial construction and had been improperly rebuilt and maintained after partial breaches. It was the final failure after a wet spring and heavy rainfall that resulted in death and devastation along the Little Conemaugh River valley from South Fork to Johnstown. This field guide presents the history of the South Fork Dam and incorporates recent studies that examined the timing of the flood and failure of the dam itself. The field trip begins at the origin of the flood at the South Fork Dam and largely follows the path of the flood down the valley to Johnstown with stops at sites impacted by the flood wave, as well as sites that demonstrate a response to the flood.
This volume includes seven field guides that explore the diverse geology of Virginia from its Appalachian highlands to the Atlantic shore. The guides cover an array of topics ranging from cave and karst development in the Valley and Ridge to the exceptional fossil localities at the Carmel Church Quarry and the cliffs near Stratford Hall to Precambrian rocks in the Blue Ridge Mountains. Three guides focus on the Paleozoic to Proterozoic tectonic history of the Blue Ridge and Piedmont provinces, two guides discuss the stratigraphy and fossil assemblages preserved in Cenozoic deposits on the Atlantic Coastal Plain, one guide examines Paleozoic stratigraphy and cave formation in western Virginia, and the final guide explores the relationship between the geology of the Fall Zone and the Civil War during the Petersburg Campaign in 1864–1865.
This volume includes seven field guides that explore the diverse geology of Virginia from its Appalachian highlands to the Atlantic shore. The guides cover an array of topics ranging from cave and karst development in the Valley and Ridge to the exceptional fossil localities at the Carmel Church Quarry and the cliffs near Stratford Hall to Precambrian rocks in the Blue Ridge Mountains. Three guides focus on the Paleozoic to Proterozoic tectonic history of the Blue Ridge and Piedmont provinces, two guides discuss the stratigraphy and fossil assemblages preserved in Cenozoic deposits on the Atlantic Coastal Plain, one guide examines Paleozoic stratigraphy and cave formation in western Virginia, and the final guide explores the relationship between the geology of the Fall Zone and the Civil War during the Petersburg Campaign in 1864–1865.
This volume includes seven field guides that explore the diverse geology of Virginia from its Appalachian highlands to the Atlantic shore. The guides cover an array of topics ranging from cave and karst development in the Valley and Ridge to the exceptional fossil localities at the Carmel Church Quarry and the cliffs near Stratford Hall to Precambrian rocks in the Blue Ridge Mountains. Three guides focus on the Paleozoic to Proterozoic tectonic history of the Blue Ridge and Piedmont provinces, two guides discuss the stratigraphy and fossil assemblages preserved in Cenozoic deposits on the Atlantic Coastal Plain, one guide examines Paleozoic stratigraphy and cave formation in western Virginia, and the final guide explores the relationship between the geology of the Fall Zone and the Civil War during the Petersburg Campaign in 1864–1865.
Prepared in conjunction with the 2015 GSA Annual Meeting in Baltimore, Maryland, this volume contains guides to field trips in this historic region. Emanating from the Fall Line city of Baltimore, these trips reflect the diversity of geological features in the mid-Atlantic region including the Piedmont, Appalachian Mountains, and Coastal Plain, and the importance of geology on the development and construction of the Baltimore-Washington, D.C., metropolitan area. Trips to the core of the Appalachian orogen concern themselves with the tectonic and metamorphic history, early Paleozoic carbonate platform development, Devonian paleoclimate, and coal-mine fire hazards. Excursions to the Coastal Plain examine various aspects of Cenozoic stratigraphy, structure, barrier island formation, and wetland and ecosystem development. A variety of trips also explore urban geology, including building and monument stones of Baltimore and Washington, D.C., urban hydrogeology, and Civil War battlefield geology.
The Middle Fork Nooksack River drains the southwestern slopes of the active Mount Baker stratovolcano in northwest Washington State. The river enters Bellingham Bay at a growing delta 98 km to the west. Various types of debris flows have descended the river, generated by volcano collapse or eruption (lahars), glacial outburst floods, and moraine landslides. Initial deposition of sediment during debris flows occurs on the order of minutes to a few hours. Long-lasting, down-valley transport of sediment, all the way to the delta, occurs over a period of decades, and affects fish habitat, flood risk, gravel mining, and drinking water.Holocene lahars and large debris flows (>10(6) m(3)) have left recognizable deposits in the Middle Fork Nooksack valley. A debris flow in 2013 resulting from a landslide in a Little Ice Age moraine had an estimated volume of 100,000 m(3), yet affected turbidity for the entire length of the river, and produced a slug of sediment that is currently being reworked and remobilized in the river system. Deposits of smaller-volume debris flows, deposited as terraces in the upper valley, may be entirely eroded within a few years. Consequently, the geologic record of small debris flows such as those that occurred in 2013 is probably very fragmentary. Small debris flows may still have significant impacts on hydrology, biology, and human uses of rivers downstream. Impacts include the addition of waves of fine sediment to stream loads, scouring or burying salmon-spawning gravels, forcing unplanned and sudden closure of municipal water intakes, damaging or destroying trail crossings, extending river deltas into estuaries, and adding to silting of harbors near river mouths.
The Anaconda and Bitterroot metamorphic core complexes are located in western Montana, along the eastern edge of the Cordilleran hinterland. This multi-tiered extensional terrain contains exceptional exposures that collectively exhibit a crustal cross section through orogenic continental crust (i.e., middle through upper crust). The core complex footwall rocks consist of Late Cretaceous arc-related plutons and Eocene granitic plutons intruded into deformed and metamorphosed Midproterozoic Belt Supergroup and Paleozoic to Cretaceous shelf-platform strata. Late Cretaceous shear zones and folds dominate footwall structure, representing significant thinning of the stratigraphic section. Eocene detachments, mylonites, and plutonic suites distinctly overprint the Late Cretaceous structures. A stark example of this Eocene overprint is the Anaconda detachment, which resulted in eastward translation of the Late Cretaceous, arc-related Boulder batholith. This field trip will cover a transect through the Anaconda core complex from the Philipsburg valley to Butte, Montana. Field trip participants will examine key locations that clarify the distinction between the timing and structural style of Late Cretaceous crustal thickening and/or collapse features versus those related to Eocene core complex development.
This field guide describes a three-day trip from Vancouver, British Columbia, to the Wells Gray-Clearwater volcanic field (WGCVF) in east-central British Columbia. The WGCVF is the site of transitional to alkali olivine basaltic volcanism erupted over the last three million years. The small volume magmas (< 1 km(3)) erupted along preexisting normal faults related to the late stages of Cordilleran terrane amalgamation, along the boundary between the miogeoclinal and pericratonic rocks of the Kootenay terrane and the allochthonous Slide Mountain and Quesnellia terranes west of ancestral North America. The magmas are highly enriched in incompatible elements, especially large-ion lithophile elements, and are interpreted as the result of low degrees of partial melting of a heterogeneous, metasomatized mantle. Upon ascent through the crust, they carried up both crustal and mantle xenoliths. During the eruptive period of the WGCVF, at least four glacial periods have occurred. The interplay between volcanism and glaciation is captured in the wide range of volcanic features found in the region. Field trip participants will view numerous diverse volcanic landforms and deposits: from tuyas to ice-marginal valley-edge deposits, volcanoclastic-lacustrine deposits, and associated pillow lavas and hyaloclastites.
As the late Pleistocene Cordilleran Ice Sheet (CIS) retreated from the southern Puget Lowland and thinned rapidly, marine waters invaded the central and northern lowland, floating the residual ice and causing wholesale collapse of the CIS from southern Whidbey Island to southern British Columbia. Massive, poorly sorted Everson glaciomarine drift was deposited contemporaneously over the entire central and northern lowland. More than 160 C-14 dates show that the Everson interval began 12,500 C-14 yr B.P. and ended 11,700 C-14 yr B. P. Numerous marine strandlines record the drop in relative sea level in the Fraser Lowland from similar to 180 m (600 ft) at the end of the Everson interval to near present sea level.Following emergence of the Fraser Lowland, a lobe of the CIS advanced from the Fraser Canyon near Sumas to Bellingham during the Sumas Stade. As the ice retreated, at least eight end moraines were built successively across the lowland, each marking a position of ice advance or stillstand that records late Pleistocene climatic fluctuations. About 40 new C-14 dates indicate that the ages of these moraines span the Inter-Allerod-Younger Dryas intervals between 11,700 and 10,000 C-14 yr B. P. The C-14 chronology allows correlation of the Sumas moraines with moraines in the Cascade Range, Rocky Mountains, Canada, Scandinavia, the European Alps, New Zealand, South America, and elsewhere. Late in the retreat of the ice, large outburst floods from an ice-dammed lake in British Columbia swept across the Sumas outwash plain, resulting in fluted topography and giant ripples on dune forms.
This trip through SW British Columbia focuses on past and ongoing land movements and flood events, and archaeological sites likely affected by these events. Our route follows a varied terrain of landforms inhabited for millennia by First Nations.
A ruling hypothesis for the central Cascade Range in Washington is that the Eocene arkosic formations, which are kilometers thick, were deposited in local grabens, such as the Chumstick Formation in the putative Chiwaukum graben. However, the formations are regional in extent and are preserved in less extensive northwest-trending synclines. The Chumstick Formation in the Peshastin syncline is a more proximal equivalent of the Roslyn Formation, which is preserved in the Kittitas Valley syncline 25 km to the southwest.The Chiwaukum structural low is partially bounded on the southwest by the Leavenworth fault zone, which consists of northwesterly striking, northeasterly verging reverse faults (with associated northwest-striking folds). The reverse faults and the hinges of the folds are cut by N-S, dextral strike-slip faults, which also partially bound the Chiwaukum structural low. Conglomeratic units in the Chumstick Formation are not proximal to either set of bounding faults.The Leavenworth fault occurs on the steeper northeastern limb of a northwesterly trending, basement-cored anticline. The Eagle Creek and Ainsley Canyon anticlines also have reverse faults on their steeper northeastern limbs. In the Puget Lowland, the Seattle reverse fault is in a similar anticline.The regional distribution of the Eocene formations and uplift of the Cascade Range are caused by folding of the Miocene Columbia River Basalt Group since 4 Ma. The remnant of a 4 Ma andesite on Natapoc Mountain shows that the present low topography of the Chiwaukum structural low is erosional and young.
The natural landscape of the North Shore of Vancouver is a mountainous one extending from sea level to similar to 1400 m. Land below similar to 400 m has been undergoing increasing urbanization since the 1950s. Development has encroached on areas subject to natural hazards such as floods, debris flows, slope failures, and coastal inundation. We will visit examples of these urban hazards, discuss problems of hazard identification in a forested landscape, and review urban planning and engineering responses to hazard management.
Exotic Miocene and Pliocene river gravel lies on top of the Continental Divide along the Idaho-Montana border near Monida Pass. The gravel is interlayered with tuffs and basalt flows of the Heise volcanic field, which erupted from the site of the Yellowstone hotspot between 6.62 and 4.45 Ma. The gravel includes pebbles that may have been derived from bedrock outcrops in Nevada and Utah, implying a paleo-river with headwaters to the south of the modern Continental Divide and Snake River Plain. The river may have been a tributary of the pre-ice age Bell River of Canada.The field trip examines evidence for the tectonic evolution of the Monida Pass area. The course of the Miocene river appears to have been diverted around growing mountain ranges, and then pinched off at Monida Pass on the northern shoulder of the Yellowstone hotspot track.
This field guide focuses on glacial history, dynamics and processes, and postglacial landscape adjustments in the southern Fraser Plateau region. Located between the Coast and Columbia Mountains in south-central British Columbia, Canada, the southern Fraser Plateau was near the geographic center of the last (marine oxygen isotope stage [MIS] 2) Cordilleran Ice Sheet (CIS). The transition from cold to warm-based ice during MIS 2 is recorded in till sedimentology and structural geology. The perceived absence of large deglacial recessional moraines has been used as evidence that ice regionally stagnated because of a rapid rise in equilibrium line altitude. However, glacioisostatic rebound orientations, ice-marginal channel and grounding-line and push moraine distributions, and reconstructions of late-glacial ice-marginal lake evolution suggest a systematic northwestward pattern of active ice-margin retreat toward the Coast Mountains, accompanied by regional thinning. Eskers and erosional corridors record drainage of supraglacial lakes or ice-marginal water sources in or over thin ice. Many ice-dammed lakes drained catastrophically. Following lake drainage, streams incised valley fills, leaving behind terraces capped by paraglacial fans and eolian sediment. In sum, we examine (1) valley-fill sediments that record Quaternary history dating back to the early or mid-Pleistocene; (2) till, moraines, erosional corridors, and eskers that provide evidence for MIS 2 CIS dynamics and hydrology; (3) late-glacial ice-marginal lake sediments and landforms that allow reconstruction of lake evolution and drainage, and changing ice-margin positions; and (4) the character and ages of river terraces, paraglacial fans, and eolian sediments that record the timing and nature of postglacial landscape adjustments.
On this field trip, participants will get their hands dirty while characterizing soils formed on five different rock types: Archean Gneiss, Flathead Sandstone, Wolsey Shale, Meagher Limestone, and Absaroka Volcanics (a basaltic andesite rock). We first recap prior soil survey efforts across the Gallatin National Forest in southwestern Montana and introduce a state factor approach to understanding soils. For over 50 years, Montana State University faculty have explored parts of this lithosequence, using it as a natural laboratory for thousands of students. We continue this tradition with this field guide, emphasizing how the combination of field and laboratory data can enrich our understanding of soil processes. We will observe and measure striking differences in soils; these differences in physical and chemical properties, from textures and colors to pH and elemental composition, are discussed in the context of quantifying the influence of the underlying rock on soil properties. We use these differences to ask whether heterogeneity in soil properties justifies the inference that soil properties are dominated by the underlying lithology. We conclude that the underlying rock strongly influences soil properties, but in variable ways across this lithosequence. This influence is both direct and indirect: chemical weathering of the rock leads to compositional changes in overlying soil, but rock weathering also leads to coarse fragments in the soil profile, which alters soil hydrology.
