THE MARYBOROUGH BASIN

1966 ◽  
Vol 6 (1) ◽  
pp. 30 ◽  
Author(s):  
Peter L. Ellis
Keyword(s):  
Normal Fault ◽  
Lower Triassic ◽  
Deep Drilling ◽  
Offshore Area ◽  
Eastern Margin ◽  
The North ◽  
Reservoir Potential ◽  
Structural Entity ◽  
Shallow Platform ◽  
Time Point

The Maryborough Basin, occupying an area of 9,500 square miles, developed as a structural entity in the Mesozoic. Onshore regional mapping has shown that subsidence is controlled by ancient lineaments which have a north-westerly trend. These structural lines are characterised by normal fault movements with downthrow to the east. The eastern margin of the basin has been interpreted from geophysical data as a shallow platform. The sediments of the basin were severely folded in a post-Aptian orogeny.A maximum thickness of 31,000 feet is known in the post-Permian section. Marine conditions prevailed in the Lower Triassic, and again in the Aptian when 7,000 feet of shallow-water quartzose sediments were deposited. The remainder of the section comprises continental sediments. Currents flowing from the east in Aptian time point to an emergent high in this direction. Such a high may have been downfaulted during the post-Aptian orogeny. Four thousand feet of trachyandesitic pyroclastics and tuffaceous sediments which were deposited during the Neocomian may have been derived from an oceanic eruptive zone. This possibly corresponds to the eastern margin of the basin, and also to an interpreted vental belt in the Swain Reefs area immediately to the north-west.Mesozoic and Tertiary marine rocks are possible sources of hydrocarbon. Porous Jurassic orthoquartzite has reservoir potential, but this unit may only be tested by very deep drilling. Much of the onshore Cretaceous section is known to be tight. In the offshore area, the flattening of the northwesterly plunge of the fold structures in the Cretaceous rocks, with the possibility of the development of closures, together with the known thickening of porous, marine Tertiary sediments, enhance the prospect of hydrocarbon accumulation in this area.

scholarly journals Morphotectonic Analysis along the Northern Margin of Samos Island, Related to the Seismic Activity of October 2020, Aegean Sea, Greece

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 102
Author(s):  
Paraskevi Nomikou ◽  
Dimitris Evangelidis ◽  
Dimitrios Papanikolaou ◽  
Danai Lampridou ◽  
Dimitris Litsas ◽  
...  
Keyword(s):  
Fault Zone ◽  
Seismic Activity ◽  
Volcanic Rocks ◽  
Active Tectonics ◽  
Normal Fault ◽  
Aegean Sea ◽  
Northern Margin ◽  
The North ◽  
Eastern Aegean ◽  
Half Graben

On 30 October 2020, a strong earthquake of magnitude 7.0 occurred north of Samos Island at the Eastern Aegean Sea, whose earthquake mechanism corresponds to an E-W normal fault dipping to the north. During the aftershock period in December 2020, a hydrographic survey off the northern coastal margin of Samos Island was conducted onboard R/V NAFTILOS. The result was a detailed bathymetric map with 15 m grid interval and 50 m isobaths and a morphological slope map. The morphotectonic analysis showed the E-W fault zone running along the coastal zone with 30–50° of slope, forming a half-graben structure. Numerous landslides and canyons trending N-S, transversal to the main direction of the Samos coastline, are observed between 600 and 100 m water depth. The ENE-WSW oriented western Samos coastline forms the SE margin of the neighboring deeper Ikaria Basin. A hummocky relief was detected at the eastern margin of Samos Basin probably representing volcanic rocks. The active tectonics characterized by N-S extension is very different from the Neogene tectonics of Samos Island characterized by NE-SW compression. The mainshock and most of the aftershocks of the October 2020 seismic activity occur on the prolongation of the north dipping E-W fault zone at about 12 km depth.

1750–1710 Ma deformation along the eastern margin of the North Australia Craton

2021 ◽  
Vol 353 ◽  
pp. 106019
Author(s):  
Joshua S. Spence ◽  
Ioan V. Sanislav ◽  
Paul H.G.M. Dirks
Keyword(s):  
Eastern Margin ◽  
The North

Understanding pre- and syn-orogenic tectonic evolution in western Himalaya through age and petrogenesis of Palaeozoic and Cenozoic granites from upper structural levels of Bhagirathi Valley, NW India

2021 ◽  
pp. 1-27
Author(s):  
Aranya Sen ◽  
Koushik Sen ◽  
Amitava Chatterjee ◽  
Shubham Choudhary ◽  
Alosree Dey
Keyword(s):  
Inductively Coupled Plasma ◽  
Age Distribution ◽  
Normal Fault ◽  
Western Himalaya ◽  
Indian Plate ◽  
Low Grade ◽  
Inductively Coupled ◽  
The North ◽  
Plasma Mass Spectrometry ◽  
Structural Levels

Abstract The Himalaya is characterized by the presence of both pre-Himalayan Palaeozoic and syn-Himalayan Cenozoic granitic bodies, which can help unravel the pre- to syn-collisional geodynamics of this orogen. In the Bhagirathi Valley of Western Himalaya, such granites and the Tethyan Himalayan Sequence (THS) hosting them are bound to the south by the top-to-the-N extensional Jhala Normal Fault (JNF) and low-grade metapelite of the THS to its north. The THS is intruded by a set of leucocratic dykes concordant to the JNF. Zircon U–Pb laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) geochronology of the THS and one leucocratic dyke reveals that the two rocks have a strikingly similar age distribution, with a common and most prominent age peak at ~1000 Ma. To the north of the THS lies Bhaironghati Granite, a Palaeozoic two-mica granite, which shows a crystallization age of 512.28 ± 1.58 Ma. Our geochemical analysis indicates that it is a product of pre-Himalayan Palaeozoic magmatism owing to extensional tectonics in a back-arc or rift setting following the assembly of Gondwana (500–530 Ma). The Cenozoic Gangotri Leucogranite lies to the north of Bhaironghati Granite, and U–Pb dating of zircon from this leucogranite gives a crystallization age of 21.73 ± 0.11 Ma. Our geochemical studies suggest that the Gangotri Leucogranite is a product of muscovite-dehydration melting of the lower crust owing to flexural bending in relation to steepening of the subducted Indian plate. The leucocratic dykes are highly refracted parts of the Gangotri Leucogranite that migrated and emplaced along extensional fault zones related to the JNF and scavenged zircon from the host THS during crystallization.

scholarly journals The Eastern Margin of the North Atlanic Basin

1899 ◽  
Vol 6 (5) ◽  
pp. 232-234
Author(s):  
Edward Hull
Keyword(s):  
Eastern Margin ◽  
The North

scholarly journals Synoptic fluctuation of the Taiwan Warm Current in winter on the East China Sea shelf

2016 ◽  
Author(s):  
Jiliang Xuan ◽  
Daji Huang ◽  
Thomas Pohlmann ◽  
Jian Su ◽  
Bernhard Mayer ◽  
...  
Keyword(s):  
Ocean Model ◽  
Coastal Current ◽  
Gradient Term ◽  
Taiwan Warm Current ◽  
Offshore Area ◽  
Warm Current ◽  
Geostrophic Balance ◽  
The North ◽  
The Cross ◽  
The Taiwan Strait

Abstract. The seasonal mean and synoptic fluctuation of the wintertime Taiwan Warm Current (TWC) were investigated using a well validated finite volume community ocean model. The spatial distribution and dynamics of the synoptic fluctuation were highlighted. The seasonal mean of the wintertime TWC has two branches: an inshore branch between the 30 and 100 m isobaths and an offshore branch between the 100 and 200 m isobaths. The Coriolis term is much larger than the inertia term and is almost balanced by the pressure gradient term in both branches, indicating the geostrophic balance of the mean current. Two areas with significant fluctuations of the TWC were identified during wintertime. One of the areas is located to the north of Taiwan with velocities varying in the cross-shore direction. These significant cross-shore fluctuations are driven by barotropic pressure gradients associated with the intrusion of the Taiwan Strait Current (TSC). When a larger TSC intrudes north of Taiwan, the isobaric slope tilts downward from south to north, leading to a cross-shore current from the coastal area to the offshore area. When the TSC intrusion is weak, the cross-shore current to the north of Taiwan is directed from offshore to inshore. The other area of significant fluctuation is located in the inshore area, extending in the region between the 30 and 100 m isobaths. The fluctuations are generally strong in the alongshore direction, in particular at the latitudes 26.5° N and 28° N where they are important for the local cross-shore transports. Wind affects the synoptic fluctuation through episodic events. When the northeasterly monsoon prevails, the southward Zhe-Min Coastal Current dominates the inshore area associated with a deepening of the mixed layer. When the winter monsoon is weakened or the southerly wind prevails, the northward TWC dominates in the inshore area.

scholarly journals Geological Structure Analysis to Determine the Direction of the Main Stress at Western Part of Kolok Mudik, Barangin District, Sawahlunto, West Sumatera

2017 ◽  
Vol 2 (1) ◽  
pp. 46
Author(s):  
Miftahul Jannah ◽  
Adi Suryadi ◽  
Muchtar Zafir ◽  
Randi Saputra ◽  
Ihsanul Hakim ◽  
...  
Keyword(s):  
Structure Analysis ◽  
Normal Fault ◽  
Geological Structure ◽  
Reverse Fault ◽  
Geological Structures ◽  
The North ◽  
Main Stress

On the study area there are three types of structure, those are fault, fold and joint. Types of fault were found  in the study area, reverse fault with the strike/dip is N215oE/75o, normal fault has a fault directions N22oE and N200oE with pitch 35o, and dextral fault with pitch 10o and strike N219oE. Fold and joint structures used to determine the direction of the main stress on the study area. Further, an analysis used stereonet for data folds and joints. So that from the data got three directions of main stress, those are Northeast – Southwest (T1), North – South (T2) and Southeast – Northwest (T3). On the Northeast – Southwest (T1) stress there are four geological structures, anticline fold at ST.3 , syncline folds at ST. 13a, ST. 13b, ST. 13c and ST. 33, chevron fold at ST. 44 and joint at ST. 2. On the North – South (T2) stress there are three geological structures, those are syncline fold at ST. 35, anticline fold at ST. 54 and joints at ST. 41, ST. 46 and ST. 47. On the Southeast – Northwest (T3) stress were also three geological structures, those are chevron fold at ST 42a, overturned fold at ST. 42b, syncline fold at ST. 42c and joints at ST. 5 and ST. 34.

scholarly journals The 31 March 2020 Mw 6.5 Stanley, Idaho, Earthquake: Seismotectonics and Preliminary Aftershock Analysis

2020 ◽  
Author(s):  
Lee M. Liberty ◽  
Zachery M. Lifton ◽  
T. Dylan Mikesell
Keyword(s):  
Surface Displacement ◽  
Volcanic Belt ◽  
Normal Fault ◽  
Fault System ◽  
Basin And Range Province ◽  
Ground Shaking ◽  
The North ◽  
Show Evidence ◽  
Tectonic Framework ◽  
Tectonic Belt

Abstract We report on the tectonic framework, seismicity, and aftershock monitoring efforts related to the 31 March 2020 Mw 6.5 Stanley, Idaho, earthquake. The earthquake sequence has produced both strike-slip and dip-slip motion, with minimal surface displacement or damage. The earthquake occurred at the northern limits of the Sawtooth normal fault. This fault separates the Centennial tectonic belt, a zone of active seismicity within the Basin and Range Province, from the Idaho batholith to the west and Challis volcanic belt to the north and east. We show evidence for a potential kinematic link between the northeast-dipping Sawtooth fault and the southwest-dipping Lost River fault. These opposing faults have recorded four of the five M≥6 Idaho earthquakes from the past 76 yr, including 1983 Mw 6.9 Borah Peak and the 1944 M 6.1 and 1945 M 6.0 Seafoam earthquakes. Geological and geophysical data point to possible fault boundary segments driven by pre-existing geologic structures. We suggest that the limits of both the Sawtooth and Lost River faults extend north beyond their mapped extent, are influenced by the relic trans-Challis fault system, and that seismicity within this region will likely continue for the coming years. Ongoing seismic monitoring efforts will lead to an improved understanding of ground shaking potential and active fault characteristics.

scholarly journals The 2011 Oichalia (SW Peloponnese, Greece) seismic swarm: Geological and seismological evidence for E-W extension and reactivation of the NNW-SSE striking Siamo Fault

2016 ◽  
Vol 46 ◽  
pp. 81 ◽  
Author(s):  
A. Ganas ◽  
E. Lekkas ◽  
M. Kolligri ◽  
A. Moshou ◽  
K. Makropoulos
Keyword(s):  
Normal Fault ◽  
Severe Damage ◽  
Damage Distribution ◽  
Field Orientation ◽  
Axis Orientation ◽  
Geological Evidence ◽  
Seismic Swarm ◽  
The North ◽  
Seismological Data ◽  
The Village

The Upper Messinia basin (Peloponnese, Greece) hosted a seismic swarm during the second half of 2011. The geological evidence (surface breaks striking N160°E), the seismological data (distribution of relocated earthquakes and T-axis orientation) and severe damage distribution are aligned along the eastern margin of the basin, so as they are attributed to reactivation of the bordering NNW-SSE normal fault. In particular, the rupture of the 14 August 2011 M=4.8 event is associated to the surface breaks inside the village Siamo. The length of the reactivated fault is estimated as 7 ±1 km based on the longest dimension (NW-SE) of the swarm epicentres (June to October 2011). The mode of rupture of the Siamo fault is probably related to a) the change in stress field orientation from south to north inside the basin (from E-W extension in the Siamo – Katsaro area to N-S extension in the north of Oichalia area) and/or b) to the occurrence of magmatic fluids due to the proximity of Messinia to the Hellenic subduction.

Nouvelles observations sur la serie de la Gara Sayada (bordure nord-est de l'Eglab, Sahara occidental)

1961 ◽  
Vol S7-III (2) ◽  
pp. 127-132
Author(s):  
Pierre Dourthe ◽  
O. Serra
Keyword(s):  
Western Sahara ◽  
Eastern Margin ◽  
The North ◽  
North Eastern

Abstract A subhorizontal sandy series, the Gara Sayada series, some hundreds of meters thick, overlies a folded sandstone-shale series, more than 1,000 meters thick, on the north-eastern margin of the Eglab massif (Algeria) in the western Sahara. The intra-Caradocian (Ordovician) unconformity already known at several other localities in the Sahara is thus also represented in this region.

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