Top Of Basement Research Articles

Temperature in the subsurface of the Swiss and German Alpine Foreland

The mean temperature gradient maps from surface down to top basement and down to base Tertiary correspond to the boundaries and internal features of the basin. The Landshut-Neuötting High in Eastern Bavaria is an area of relatively high temperature. The German Eastmolasse part west of this high shows extremely low temperature gradients. In the German Westmolasse area, in addition to a normal Tertiary gradient of about 25°C/km which is assumed to be the Tertiary paleogradient a steep near-surface gradient down to 500–800 m depth is deduced from the present interpretation of the measurements so that due to the southward increasing sediment thickness of the Tertiary in the flat northern margin of the basin there results a higher Tertiary mean gradient than in the south. The intramesozoic gradients are somewhat irregular, but generally tend to increase from north to south. Thus far they compensate to a certain degree the regional trend of the Tertiary gradients so that the mean gradients from surface down to top basement show smaller differences than the mean Tertiary gradients. A slight increase of the Mesozoic temperature gradients as compared with the Tertiary gradients is interpreted by both the lower heat conductivity of the consolidated and carbonate-rich Mesozoic and the northward directed water flow in the Malm karst transporting heat from the deeper southern part of the basin within the Malm karst northward at least since Pliocene time.

The 1978 Yellowstone‐Eastern Snake River Plain Seismic Profiling Experiment: Data and upper crustal structure of the Yellowstone Region

Eleven in‐line refraction profiles, recorded to distances of 300 km, and one azimuthal fan plot were constructed from data recorded with a 150‐station array in the Yellowstone National Park area during the 1978 Yellowstone‐Snake River Plain seismic experiment. Interpretations of the data suggest that the crustal P wave velocity model for the Yellowstone region is characterized by (1) an averaged 10‐km‐thick upper crustal layer, Vp = 6.0 km/s, (2) an average crustal velocity of 6.3 km/s, and (3) a total crustal thickness of 44 km. Velocity models are presented for profiles that emphasize the upper crust and show (1) a decrease in the depth to the top of the upper crustal crystalline basement from 5 km in southwestern Yellowstone near Island Park to 1 km at the northeast side of the Yellowstone Plateau that is interpreted as a progressive thinning of the silicic surface volcanic layer to the northeast and (2) evidence for a large lateral inhomogeneity interpreted to be a low‐velocity body, with a decrease of at least 10% in P wave velocity, located beneath the northeast corner of the Yellowstone Plateau. The low‐velocity zone coincides with a local −30‐mgal residual gravity anomaly and is located beneath part of the Sour Creek resurgent dome and part of the Hot Springs Basin, the largest hydrothermal system in Yellowstone. The low‐velocity body has a maximum depth to the top of 3 km and a minimum depth to the bottom of 9 km and may represent a zone of partial melt. In comparison to the thermally undisturbed upper crust of the surrounding Rocky Mountains the upper crust of the northeastern Yellowstone Plateau appears laterally inhomogeneous in velocity and layer thickness, suggesting effects of thermal and magma intrusion, whereas the lower crust appears relatively homogeneous.

Deep Stratigraphy and Evolution of Baltimore Canyon Trough Based on Multifold Seismic Reflection, Refraction, Gravity, and Magnetic Data: ABSTRACT

A recent 48-channel seismic reflection profile (U.S. Geological Survey line 25) extends 330 km southeast off southern New Jersey and crosses the widest and deepest part of the Baltimore Canyon Trough (10 km southwest of the COST B-3 well). The profile has been migrated and converted to depth to reveal the deep sedimentary and basement structures across the ocean-continent transition zone. The sedimentary wedge thickens from 5 km nearshore to 17 km just landward of the East Coast Magnetic Anomaly (ECMA; 20 km landward of the shelf edge in this area). A strong, flat reflector about 10 km wide exists at a depth of 14 km, directly beneath ECMA. Acoustic basement becomes obscure and appears to rise to a depth of 5 km over the next 40 km to the southeast, beneath a Jurassic and lower Cretaceous carbonate shelf-edge complex which extends 20 km seaward of the present shelf edge. Landward-dipping continental rise sediments exist to a depth of at least 13 km on the seaward side of the Jurassic shelf edge. The top of oceanic basement is first seen as a set of prominent hyperbolic reflectors about 50 km seaward of the Jurassic shelf edge, where it occurs at 11 km depth and dips gently landward. It is obscured landward of this point by the prominent middle Jurassic (J3) horizon. A Jurassic and lower Cretaceous shelf-edge carbonate platform or reef complex prograded 40 km out over oceanic crust in this area. Greater differential subsidence and compaction of the basin west of the ECMA have produced back-tilted and arched horizons in the Jurassic and lower Cretaceous shelf edge units, creating a 20-km-wide with 500-m closure beneath the upper continental slope. Other lines to the southwest indicate the anticlinal arch extends at least 40 km to the southwest. Similar slope anticline structures have been reported off northwest Africa. End_of_Article - Last_Page 715------------

Seismic refraction study of the continental edge off the eastern united states

Three long, strike-parallel, seismic-refraction profiles were made on the continental shelf edge, slope and upper rise off New Jersey during 1975. The shelf edge line lies along the axis of the East Coast Magnetic Anomaly (ECMA), while the continental rise line lies 80 km seaward of the shelf edge. Below the unconsolidated sediments (1.7–3.6 km/sec), high-velocity sedimentary rocks (4.2–6.2 km/sec) were found at depths of 2.6–8.2 km and are inferred to be cemented carbonates. Although multichannel seismic-reflection profiles and magnetic depth-to-source data predicted the top of oceanic basement at 6–8 km beneath the shelf edge and 10–11 km beneath the rise, no refracted events occurred as first arrivals from either oceanic basement (layer 2, approximately 5.5 km/ sec) or the upper oceanic crust (layer 3A, approximately 6.8 km/sec). Second arrivals from 10.5 km depth beneath the shelf edge are interpreted as events from a 5.9 km/sec refractor within igneous basement. Other refracted events from either layers 2 or 3A could not be resolved within the complex second arrivals. A well-defined crustal layer with a compressional velocity of 7.1–7.2 km/sec, which can be interpreted as oceanic layer 3B, occurred at 15.8 km depth beneath the shelf and 12.9 km beneath the upper rise. A well-reversed mantle velocity of 8.3 km/sec was measured at 18–22 km depth beneath the upper continental rise. Comparison with other deep-crustal profiles along the continental edge of the Atlantic margin off the United States, specifically in the inner magnetically quiet zone, indicates that the compressional wave velocities and layer depths determined on the U.S.G.S. profiles are very similar to those of nearby profiles. This suggests that the layers are continuous and that the interpretation of the oceanic layer 3B under the shelf edge east of New Jersey implies progradation of the shelf outward over the oceanic crust in that area. This agrees with magnetic anomaly evidence which shows the East Coast Magnetic Anomaly landward of the shelf edge off New Jersey and with previous seismic reflection data which reveal extensive outbuilding of the shelf edge during the Jurassic and Lower Cretaceous, probably by carbonate bank-margin accretion.

Terminal del aeropuerto de Colonia - Alemania Federal

This terminal has two basements, ground floor and five higher floor levels. The lower basement has reserve water storage tanks heating and air conditioning plant and other services. The top basement contains telephone exchanges, transformer plant and further ancillary facilities. Passenger arrivals are located on the ground floor, and this includes customs and traffic police offices, distinguished passengers reception rooms, an auditorium, luggage distribution installations and waiting rooms. The second floor is devoted to passenger departure facilities, which includes a reception hall, waiting zones, information centre, offices, and the desks of the air companies. On the third floor there are two independent restaurants, for national and international flights. The fourth floor contains air traffic control services, including a metereological office, and on the fifth floor there is a visitors coffee shop and a large terrace.

Basement Beneath Atlantic Coastal Plain Between New York and Georgia: ABSTRACT

Basement is defined, for the purposes of this discussion, as the metamorphic and (or) igneous rocks below End_Page 1246------------------------------ which there is no known stratigraphic or structural break. At least 300 holes have penetrated basement beneath the Mesozoic and Cenozoic sediments of the Atlantic Coastal Plain between New York and Georgia. Approximately 90 per cent of them penetrated basement at elevations above--1,000 feet M.S.L. The 10,054-foot Esso #1 Hatteras Light well, which encountered the top of basement at--9,954 feet M.S.L., is deepest. Drill hole plus meager geophysical data support the following tentative conclusions. Precambrian and Paleozoic metamorphic and igneous (including volcanic) rocks, similar to those exposed on the Piedmont to the west, constitute basement. Many of these rocks have been highly fractured and sheared. Part of the rocks accumulated in a pre-Mesozoic eugeosyncline. From at least late Mesozoic time the basement surface has played the role of a differentially warping platform. At least four periods of diastrophism are known to have occurred in this area. The regional structural (and topographical) trend is northeast-southwest. The surface of the basement may be characterized as an old age erosion surface--commonly referred to as the Fall Zone peneplain--with sporadic fault troughs, ridges, valleys, and arches. Locally some of the rocks have been weathered to depths exceeding 150 feet. The basement surface dips generally seawardly from 15-40 feet per mile (with about 35 feet per mile typical) to approximately the--2,250-foot M.S.L. contour; seaward from this contour it steepens to about 100-125 feet per mile. Oil may occur in commercial quantities in weathered zones on or fractured zones in the basement or in sedimentary rocks that lens out against topographic highs on the basement surface. End_of_Article - Last_Page 1247------------