Geodynamic significance of a buried transient Carboniferous landscape

2021 ◽  
Author(s):  
Fergus McNab ◽  
Nicky White
Keyword(s):  
Temperature Anomaly ◽  
Marine Invertebrate ◽  
Grand Canyon ◽  
Indirect Evidence ◽  
Significant Implication ◽  
Dynamic Topography ◽  
Transient Event ◽  
Base Level ◽  
Aeolian Deposits ◽  
Invertebrate Fossils

It is increasingly clear that present-day dynamic topography on Earth, which is generated and maintained by mantle convective processes, varies on timescales and length scales on the order of 1−10 m.y. and 103 km, respectively. A significant implication of this behavior is that Phanerozoic stratigraphic records should contain indirect evidence of these processes. Here, we describe and analyze a well-exposed example of an ancient landscape from the Grand Canyon region of western North America that appears to preserve a transient response to mantle processes. The Surprise Canyon Formation lies close to the Mississippian-Pennsylvanian boundary and crops out as a series of discontinuous lenses and patches that are interpreted as remnants of a westward-draining network of paleovalleys and paleochannels within a coastal embayment. This drainage network is incised into the marine Redwall Limestone whose irregular and karstified upper surface contains many caves and collapse structures. The Surprise Canyon Formation itself consists of coarse imbricated conglomerates, terrestrial plant impressions including Lepidodendron, and marine invertebrate fossils. It is overlain by marine, fluvial, and aeolian deposits of the Supai Group. These stratal relationships are indicative of a transient base-level fall whose amplitude and regional extent are recognized as being inconsistent with glacio-eustatic sea-level variation. We propose that this transient event is caused by emplacement and decay of a temperature anomaly within an asthenospheric channel located beneath the lithospheric plate. An analytical model is developed that accounts for the average regional uplift associated with landscape development and its rapid tectonic subsidence. This model suggests that emplacement and decay of a ∼50 °C temperature anomaly within a channel that is 150 ± 50 km thick can account for the observed vertical displacements. Our results are corroborated by detrital zircon studies that support wholesale drainage reorganization at this time and by stratigraphic evidence for spatially variable regional epeirogeny. They are also consistent with an emerging understanding of the temporal and spatial evolution of the lithosphere-asthenosphere boundary.

Vertical movement at the Alpine-Carpathian border (Hainburg Hills) calculated from numerical ages of cave sediments

2020 ◽  
Author(s):  
Lukas Plan ◽  
Stephanie Neuhuber ◽  
Susanne Gier ◽  
Esther Hintersberger ◽  
Christopher Lüthgens ◽  
...  
Keyword(s):  
Vertical Displacement ◽  
Vertical Movement ◽  
Danube River ◽  
Age Dating ◽  
Vienna Basin ◽  
Danube Basin ◽  
Base Level ◽  
Pristine Sample ◽  
Aeolian Deposits ◽  
Bedrock Surface

<p>The Hainburg Hills form an elevated range at the south of the Male Karpaty mountains and separate the Vienna Basin from the Danube Basin. They consist of Variscian magmatic and metamorphic rocks covered with anchimetamorphic Mesozoic carbonates. The area west of the Hainburg Hills is well-known for its thermal sulfuric spa since Roman times. About 30 karst caves have been mapped in the area that show signs of hydrothermal or sulphuric acid speleogenesis.</p><p>Two of these caves vertically separated by 92 m were numerically dated using terrestrial cosmogenic <sup>26</sup>Al and <sup>10</sup>Be in quartz washed into a cave and <sup>230</sup>Th/U of calcite rafts. In addition, aeolian cover sediments were investigated using luminescence age dating.</p><p>The upper c. 15 m wide and c. 20 m high cave chamber was completely filled with large, well-rounded quartz cobbles in a red matrix. The matrix contains over 30% clay and consists of quartz, K-feldspar, muscovite, chlorite, hematite, kaolinite, illite, and smectite. The occurrence of smectite in combination with the small grain size indicates soil forming processes in the B-horizon. We conclude that fluvial gravels –similar to modern ones of the Danube river - were transported into the cave together with a matrix originating from a soil cover. In-situ produced cosmogenic <sup>10</sup>Be and <sup>26</sup>Al in five quartz cobbles was used to calculate the time of sediment emplacement into the cave. Results indicate a depositional age of c. 4.5 Ma using the isochron technique.</p><p>The lower cave was investigated using calcite rafts that form at the surface of cave pools using the <sup>230</sup>Th/U dating method. One sample of thin, sharp-edged, and uncoated cave rafts gave the youngest age of c.0.32 Ma. Two other samples were more overgrown and gave older ages between 0.38 and 0.44 Ma. The pristine sample is best suited to reflect the time when the base level was close to the cave.</p><p>Rates of vertical displacement vary between 30 and 35 m/Ma for the last 4 Ma and between 150 and 160 m/Ma for the last 0.32 Ma and document an increase of uplift/incision for the region. These numbers compare well to published rates from the unglaciated surroundings that also range from a maximum of 140 m/Ma to a minimum of 20-25 m/Ma and are generally much lower compared to formerly glaciated areas in the Alps and GPS measured uplift (c. 1000 m/Ma).</p><p>The luminescence age of 14.6 ± 0.1 ka recorded in cover sands show that sediments they overly much older gravels. This implies sediments were repeatedly eroded from the top of the karstified bedrock surface. The aeolian sediments are primarily preserved in depressions within the bedrock surface. Therefore, the age may represent the end of a phase of intense aeolian activity when wind velocities decreased sufficiently to cause sand accumulation. This period is the peak in Western and Central Europe periglacial activity and accompanied by formation of aeolian deposits. The ages are comparable to aeolian deposits in the Vienna Basin area and cover sediments from the Transdanubian Range.</p>

scholarly journals Jurassic animals and algae in the flooring of Our Lady of Sorrows Church in Poznań

2015 ◽  
Vol 52 (1-2) ◽  
pp. 37-43
Author(s):  
Mateusz Antczak
Keyword(s):  
Marine Invertebrate ◽  
Genus Level ◽  
Holy Cross Mountains ◽  
Jurassic Rocks ◽  
Invertebrate Fossils ◽  
Tectonic Movements

Abstract The flooring of Our Lady of Sorrows Church in Poznań is made of Jurassic rocks from the Świętokrzyskie Mountains (also known as Holy Cross Mountains) and contain abundant marine invertebrate fossils: sponges, bivalves, brachiopods, various families of cephalopods, etc. Some of them can be identified to the genus level. The fossils make it possible to describe the environment and ecosystem of the Jurassic sea and biostratigraphy of the sediment. There are also some significant inorganic structures, which suggest post-diagenetic tectonic movements.

Redefining the age of the lower Colorado River, southwestern United States

Geology ◽  
2021 ◽  
Author(s):  
R.S. Crow ◽  
J. Schwing ◽  
K.E. Karlstrom ◽  
M. Heizler ◽  
P.A. Pearthree ◽  
...  
Keyword(s):  
United States ◽  
Gulf Of California ◽  
Colorado River ◽  
Grand Canyon ◽  
Plate Motion ◽  
Southwestern United States ◽  
Northern Mexico ◽  
Base Level ◽  
Salton Trough ◽  
Lower Colorado River

Sanidine dating and magnetostratigraphy constrain the timing of integration of the lower Colorado River (southwestern United States and northern Mexico) with the evolving Gulf of California. The Colorado River arrived at Cottonwood Valley (Nevada and Arizona) after 5.24 Ma (during or after the Thvera subchron). The river reached the proto–Gulf of California once between 4.80 and 4.63 Ma (during the C3n.2r subchron), not at 5.3 Ma and 5.0 Ma as previously proposed. Duplication of section across newly identified strands of the Earthquake Valley fault zone (California) probably explains the discrepancy. The data also imply the start of focused plate motion and basin development in the Salton Trough (California) at 6–6.5 Ma and relative tectonic stability of the southernmost part of the lower Colorado River corridor after its integration. After integration, the Colorado River quickly incised through sediment-filled basins and divides between them as it also likely excavated Grand Canyon (Arizona). The liberated sediment from throughout the system led to deposition of hundreds of meters of Bullhead Alluvium downstream of Grand Canyon after 4.6 Ma as the river adjusted to its lower base level.

Erosion rates and patterns in a transient landscape, Grand Staircase, southern Utah, USA

Geology ◽  
2019 ◽  
Vol 47 (9) ◽  
pp. 811-814 ◽  
Author(s):  
Kerry E. Riley ◽  
Tammy M. Rittenour ◽  
Joel L. Pederson ◽  
Patrick Belmont
Keyword(s):  
Grand Canyon ◽  
Climatic Forcing ◽  
Sediment Storage ◽  
Erosion Rates ◽  
Base Level ◽  
Rock Types ◽  
Alluvial Sediment ◽  
Dynamic Landscapes ◽  
Cosmogenic 10Be

AbstractCosmogenic 10Be concentrations in alluvial sediment are widely used to infer long-term, catchment-averaged erosion rates based on the assumption that the landscape is in mass-flux steady state. However, many landscapes are out of equilibrium over millennial time scales due to tectonic and climatic forcing. The Grand Staircase of the Colorado Plateau (North America) is a transient landscape, adjusting to base-level fall from the carving of the Grand Canyon, and is characterized by cliff-bench topography caused by differential erosion of lithologic units. The 10Be concentrations from 52 alluvial and colluvial samples, collected in nested fashion from five catchments, produced inferred erosion rates ranging from 20 to >3500 m/m.y. (or mm/k.y.). We attribute this high variance in part to lithologic-controlled steepness and hotspots of erosion related to cliff retreat along the White Cliffs (escarpment near Mt. Carmel Junction, Utah), as well as headward drainage expansion along the uppermost Pink Cliffs (escarpment within Bryce Canyon National Park). Results from the downslope Vermillion Cliffs (near Kanab) indicate lower erosion rates despite similar slope and rock types, suggesting knick-zone migration has passed that lower region of our study area. The 10Be concentrations measured along trunk streams systematically match local, subcatchment erosion rates, with muted influence from upstream sediment sources. This is consistent with intermittent sediment conveyance between cliff and bench terrain, with sediment storage and localized release associated with ephemeral arroyo systems in the region. Therefore, while detrital cosmogenic nuclide records in transient landscapes may not directly reflect upstream catchment-averaged erosion rates, 10Be inventories can provide insight into unsteady upslope-directed erosion and downslope-directed sediment conveyance in these dynamic landscapes.

Pennsylvanian brachiopods from the Geumcheon-Jangseong Formation, Pyeongan Supergroup, Taebaeksan Basin, Korea

2010 ◽  
Vol 84 (3) ◽  
pp. 417-443 ◽  
Author(s):  
Sangmin Lee ◽  
Duck K. Choi ◽  
G. R. Shi
Keyword(s):  
New Species ◽  
North China ◽  
Marine Invertebrate ◽  
Late Paleozoic ◽  
Marine Environments ◽  
Faunal Composition ◽  
Taebaeksan Basin ◽  
Close Affinity ◽  
Two New Species ◽  
Invertebrate Fossils

We provide the first detailed systematic taxonomy and paleoecological investigation of late Paleozoic brachiopod faunas from Korea. Specifically, we focus on the brachiopods from the Geumcheon-Jangseong Formation, the lower part of the Pyeongan Supergroup in the Taebaeksan Basin. The formation yields a variety of marine invertebrate fossils, including brachiopods, molluscs, echinoderms, corals, fusulinids, and conodonts. Diverse brachiopods are described from six siliciclastic horizons of the formation at three localities, including 23 species belonging to 20 genera with two new species: Rhipidomella parva n. sp. and Stenoscisma wooi n. sp. Three brachiopod assemblages of the late Moscovian (Pennsylvanian) age are recognized based on their species compositions and stratigraphic distributions, namely the Choristites, Rhipidomella, and Hustedia assemblages. The brachiopod faunal composition varies within each assemblage as well as between the Assemblages, most likely reflecting local paleoenvironmental and hence paleoecological differences. The Choristites Assemblage includes relatively large brachiopods represented by Derbyia, Choristites, and Stenoscisma and may have inhabited open marine to partly restricted marine environments, whereas the Rhipidomella and Hustedia Assemblages consist of a small number of small-sized brachiopods living in lagoonal environments. The Choristites Assemblage shows a close affinity with Moscovian brachiopod assemblages in the eastern Paleo-Tethys regions, especially the Brachythyrina lata-Choristites yanghukouensis-Echinoconchus elegans Assemblage of North China, whereas the Rhipidomella and Hustedia assemblages both exhibit strong endemism.

scholarly journals Sampling-standardized expansion and collapse of reef building in the Phanerozoic

Fossil Record ◽  
2008 ◽  
Vol 11 (1) ◽  
pp. 7-18 ◽  
Author(s):  
W. Kiessling
Keyword(s):  
Fossil Record ◽  
Late Jurassic ◽  
Marine Invertebrate ◽  
Late Triassic ◽  
Late Devonian ◽  
Reef Growth ◽  
Temporal Scales ◽  
Natural Processes ◽  
Invertebrate Fossils

Tracing the variability of reef production over long temporal scales is important to approach natural processes favoring or suppressing reef growth. Raw compilations of reef abundance per unit of time do not necessarily depict biologically meaningful patterns, because the waxing and waning of reefs might just follow the quality of the fossil record, that is, the amount of paleontological information that is available in general. Here I standardize the published record of Phanerozoic reefs, as stored in the PaleoReefs database, to the published record of marine invertebrate fossils as stored in the Paleobiology Database. The sampling-standardized peaks in reef growth are essentially identical to those of previous studies, but significant peaks are rare. Times when unusual changes in ecological conditions are likely to control changes in metazoan reef proliferation were identified in the Late Devonian, Late Triassic, Late Jurassic and Neogene. <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.200700008" target="_blank">10.1002/mmng.200700008</a>

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