Disruption Of Drainage Research Articles

Mid-Cretaceous drainage reorganization and exorheic to endorheic transition in Southeast Tibet

To understand the early topographic growth of the Tibetan Plateau and the causes and effects of climate change in this region, it is important to reconstruct the drainage evolution across Southeast Tibet. Based on age constraints provided by detrital zircons in the fluvial sandstones in the Khorat Plateau Basin, we identified a major Early Cretaceous drainage disruption and reorganization event. The ages and Hf isotope compositions of the detrital zircons in the Upper Jurassic-Lower Cretaceous Phu Kradung to Phu Phan formations (166–122 Ma) suggest the existence of an exorheic continental-scale paleo-Mekong River with headwaters in the Songpan-Garze and Qiangtang terranes. This paleo-river flowed southwards across the Khorat Plateau to what is presently the offshore Phuquoc Basin, which was then part of the Neo-Tethys Ocean. In contrast, the U-Pb-Hf compositions of the detrital zircons in the Lower Cretaceous Khok Kruat Formation (122–113 Ma) indicate that a prominent detrital supply from the Sibumasu magmatic rocks was transported by the paleo-Salween River. This major change reflects the occurrence of ancestral transcontinental river disruption at around 122 Ma, which was driven by the final collision between the Lhasa and Qiangtang and Woyla Arc and Sibumasu terranes. The tectonic uplift and ensuing arid climate corresponded to the reorganization of the ancestral Mekong drainage system during the Mid-Cretaceous (113–94 Ma).

Early Middle Pleistocene drainage in southern central England

AbstractThe fluvial sequences of the Milton and the Letchworth formations in the south Midlands of England and neighbouring regions represent at least two pre-existing rivers, the Milton and Brigstock streams, underlying Middle Pleistocene glacial sediments. The Milton Formation includes sand sourced from the Midlands bedrock. This implies that both streams were aligned in a northwest to southeast direction. This direction parallels the contemporaneous courses of the rivers Thames and Trent, the former turning towards the east and northeast to enter the North Sea. Their alignments indicate that the Milton and Letchworth streams formed left-bank tributaries of the Thames, joining the river in Hertfordshire and Essex, as illustrated in the article. This reconstruction has important implications for the interpretation of the proto-Soar river of the south Midlands, represented by the Baginton Formation. Although originally thought to represent a late Middle Pleistocene line, this southwest to northeast aligned system was reinterpreted as the headwaters of a pre-Anglian ‘Bytham river’, a1ligned towards East Anglia. However, recent work has shown that this river could not have existed in the pre-Anglian since there is no link between the Midlands and East Anglian spreads. Recent re-recognition that the Baginton Formation deposits do represent a later, post-Anglian drainage line is reinforced by the identification of the Milton and Letchworth streams, whose catchments occupied the area later drained by the proto-Soar. Overall, the main drainage alignment in southern England during the pre-Anglian period was dominated by northwest–southeast-draining consequent rivers adjusted to the regional geological dip. After widespread drainage disruption caused by the Anglian glaciation, northeast–southwest-orientated subsequent streams eroded frost-susceptible clay bedrock under periglacial and permafrost conditions, and beheaded the courses of some of the older consequent streams.

The Pliocene Lost River found to west: Detrital zircon evidence of drainage disruption along a subsiding hotspot track

SHRIMP analysis of U/Pb ages of detrital zircons in twelve late Miocene to Pleistocene sand samples from six drill cores on the Snake River Plain (SRP), Idaho, suggests that an ancestral Lost River system was drained westward along the northern side of the SRP. Neoproterozoic (650 to 740 Ma, Cryogenian) detrital zircon grains from the Wildhorse Creek drainage of the Pioneer Mountains core complex, with a source in 695 Ma orthogneiss, and which are characteristic of the Big Lost River system, are found in Pliocene sand from cores drilled in the central SRP (near Wendell) and western SRP (at Mountain Home). In addition to these Neoproterozoic grains, fluvial sands sourced from the northern margin of the SRP contain detrital zircons with the following ages: 42 to 52 Ma from the Challis magmatic belt, 80 to 100 Ma from the Atlanta lobe of the Idaho batholith, and mixed Paleozoic and Proterozoic ages (1400 to 2000 Ma). In contrast, sands in the Mountain Home Air Base well (MHAB) that contain 155-Ma Jurassic detrital grains with a source in northern Nevada are interpreted to represent an integrated Snake River, with provenance on the southern, eastern and northern sides of the SRP. We propose that late Pliocene and early Pleistocene construction of basaltic volcanoes and rhyolitic domes of the Axial Volcanic Zone of the eastern SRP and the northwest-trending Arco Volcanic Rift Zone (including the Craters of the Moon volcanic center), disrupted the paleo-Lost River drainage, confining it to the Big Lost Trough, a volcanically dammed basin of internal drainage on the Idaho National Laboratory (INL). After the Axial Volcanic Zone and Arco Volcanic Rift Zone were constructed to form a volcanic eruptive and intrusive highland to the southwest, sediment from the Big Lost River was trapped in the Big Lost Trough instead of being delivered by surface streams to the western SRP. Today, water from drainages north of the SRP enters the Snake River Plain regional aquifer through sinks in the Big Lost Trough, and the water resurfaces at Thousand Springs, Idaho, about 195 km to the southwest. Holocene to latest Pliocene samples from drill core in the Big Lost Trough reveal interplay between the glacio-fluvial outwash of the voluminous Big Lost River system and the relatively minor Little Lost River system. A mixed provenance signature is recognized in fine-grained sands deposited in a highstand of a Pleistocene pluvial-lake system.

Longwall mining-induced fault reactivation and delayed subsidence ground movement in British coalfields

Faults located in areas undergoing mining subsidence during the longwall extraction of coal seams may undergo reactivation. This has been observed and documented throughout the UK (and in other major coalfields around the world) over the past 150 years. Subsidence-induced fault reactivation may cause moderate to severe damage to foundations, houses, buildings, structures and underground services, as well as damage to agricultural land through disruption of drainage and alteration of the gradient. Monitoring of faults, as they are affected by undermining, has resulted in a better understanding of fault reactivation mechanisms and of the various styles of fault reactivation, in different geological and mining settings. The duration of fault reaction is difficult to determine because of the lack of observational data. However, trough subsidence following longwall extraction of coal is rapid, often being completed within weeks to months. This is commonly followed, shortly afterwards, by a period of delayed subsidence known as residual subsidence, which in the British Coal Measures rarely accounts for more than 10% of the total subsidence. In many circumstances, where faults are not present, residual subsidence is complete within 4 months, although several cases have been recorded where subsidence effects were still being observed more than 2 years after mining had finished. Generally, it is accepted that fault reactivation sometimes may extend over the period of residual subsidence. In parts of the abandoned or partially active coalfields in the UK, relatively smaller ground movements have been observed in the vicinity of fault outcrops many years after mining has ceased. The reasons for this are not fully understood. None the less, prolonged periods of fault reactivation may have an important effect on land use and construction. The objectives of this paper are to consider fault reactivation and, in particular, to document examples of post-mining ground movements around fault outcrops and to discuss possible causal mechanisms. Features associated with these movements include increases in elevation of the ground surface and deformation (e.g. subsidence, grabens, scarps or steps, fissures, compression and tension) of the ground surface in the vicinity of faults. These features, in turn, may be associated with groundwater or mine water rebound.

The effect of an old surgical scar on sentinel node mapping in patients with breast cancer: A report of five cases

Aims To study the significance of lymphatic drainage disruption due to a surgical scar in sentinel node mapping (SNM) in breast cancer patients. Methods We reviewed patients with stage I breast cancer who had undergone SNM and had an old surgical scar in the ipsilateral breast. Results Of 534 breast cancer patients who had undergone SNM, five patients had an old scar in the ipsilateral breast. Inter-pectoral nodes, internal nodes, intramammary nodes, and contralateral axillary nodes were identified as sentinel nodes in three cases. In the remaining two cases, no sentinel lymph nodes were identified. Conclusions An old surgical scar in the breast may cause lymphatic drainage disruption, resulting in abnormal radioactive colloid uptake during SNM.

The 2002 June 22 Changureh (Avaj) earthquake in Qazvin province, northwest Iran: epicentral relocation, source parameters, surface deformation and geomorphology

SUMMARY The M w 6.4 Changureh (Avaj) earthquake occurred on 2002 June 22, in Qazvin province, northwest Iran. We use observations from seismology, field investigation and analysis of satellite imagery and digital topography to suggest that slip on a previously unrecognized thrust fault (herein named the Abdarreh fault) was responsible for the earthquake. Inversion of longperiod P and SH body wave seismograms shows rupture on a thrust fault dipping 49 ◦ to the southwest and with a centroid depth of ∼10 km. Multiple-event relocation of the main shock and aftershock epicentres and discontinuous surface ruptures observed after the earthquake are compatible with a northwest-propagating rupture on a southwest-dipping thrust, but maximum recorded displacements are much less than expected from seismology, suggesting that much of the slip failed to reach the surface and was accommodated as folding at the surface instead. Long-term folding is difficult to see in the topography of the epicentral region as the Abdarreh fold is growing through a relict Neogene topography. Anticlinal uplift can, however, be inferred from drainage disruption and stream incision. The 2002 June 22 Changureh earthquake shows the importance of being able to interpret diagnostic features of active faulting in the landscape.

Soil disturbance and five-year tree growth in a montane alternative silvicultural systems (MASS) trial

Ground-based forestry practices can negatively affect soil productivity by altering the physical, chemical, and biological properties of soil. The effect of soil disturbance on soil properties and tree growth was evaluated following single-pass hydraulic excavator and multiple-pass combined excavator and flexible track grapple skidder forwarding in four silvicultural systems treatments: Clearcut (CC), Green Tree Retention (GT), Patch Cut (PC), and Uniform Shelterwood (SW). The effectiveness of an excavator soil-rehabilitation technique (tilling) in decompacting skidtrails (i.e., reducing soil bulk density) and nutrient availability was also evaluated. Western hemlock (Tsuga heterophylla (Raf.) Sarg.) and amabilis fir (Abies amabilis Dougl. Ex. Forbes) seedlings were planted on undisturbed plots, within tracks and between tracks of skidtrails, and in rehabilitated trails within the four harvesting treatments in the spring of 1994. Seedling growth was measured after five growing seasons, and nutrient concentrations of current-year foliage were determined at the end of the fourth growing season. Seedling survival and growth was generally reduced by soil disturbances associated with skid-trails. Effects of disturbance on physical properties of soil (e.g., compaction, puddling) and disruption of drainage were the most likely causes. Nutrient deficiencies do not appear to be a factor. Nonetheless, nitrogen concentrations were lower in current-year foliage taken from rehabilitation treatments than from either undisturbed or skidtrail treatments. Effectiveness of soil rehabilitation varied. In well-drained deeper soils, tilling reduced soil bulk density to levels below those of undisturbed soils and, in the short-term (five years), improved tree growth. In wetter conditions, rehabilitation treatment decreased survival and growth of both species. Thus specific rehabilitation (tilling) prescriptions should not be universally applied across a landscape. Key words: Abies amabilis, Tsuga heterophylla, foliar analysis, soil bulk density, soil compaction, soil rehabilitation

Evolution of drainage patterns on Cape York Peninsula, northeast Queensland

Drainage patterns along passive continental margins are often hypothesised to be the result of drainage disruption following highland uplift and downwarping of the highland flank. Several studies of stream catchments throughout southeast Australia have demonstrated that the opposite tends to be the case in this region because the field evidence favours stream and continental drainage‐divide stability. While significant advances have been made towards understanding this phenomenon in the southeastern corner of the continent, little is known of the evolution of streams and highlands in northeast Australia. Our study examines palaeochannels and fluvial sedimentary units close to the continental drainage divide in six stream catchments along the length of Cape York Peninsula. The results show that four of the catchments (Barron‐Mitchell and Stewart‐Holroyd) have experienced continental divide and drainage stability, whereas the Pascoe‐Wenlock system appears to have experienced westward migration of the continental drainage divide and diversion of the Pascoe River. River diversion here is likely to be a result of the raising of base‐level and flooding of stream channels during the Cretaceous marine transgression and subsequent stream incision by the Pascoe River along structural weaknesses in the underlying strata, following cessation of marine conditions.

Accelerated uplift resulting from Anglian glacioisostatic rebound in the Middle Thames Valley, UK?: evidence from the river terrace record

A relatively simple analysis of the terraces of the Middle Thames valley reveals a complex sequence of responses to late-Anglian (late Middle Pleistocene) drainage disruption. A decrease in the amounts of vertical incision separating the later post-Anglian terraces strongly suggests a major change in the rate of incision in the Middle Thames area in the post-Anglian. A late Anglian and early post-Anglian incision rate of 1.45 m ka −1 was quickly replaced by incision at a rate of 0.089 m ka −1 in the later post-Anglian period. The lower incision rate of the later post-Anglian compares favourably with previous estimates of regional uplift. Two plausible explanations for the enhanced incision in the late Anglian and early post-Anglian are recognized, one related to ponding of the river by Anglian ice and the other to glacio-isostatic rebound. In the latter case, the mismatch between expected and actual heights of late-Anglian deposits would suggest glacio-isostatic uplift of the order of 22–25 m.

Sub‐basaltic deep‐lead systems and gold exploration at Ballarat, Australia

The Cenozoic sub‐basaltic river systems (deep leads) at Ballarat were one of the richest goldflelds in Australia during the second half of the nineteenth century. The precise courses of the deep‐lead systems have never been completely clarified, although drilling across various suggested courses of the deep leads has progressively eliminated some earlier suggestions for these courses. Two groups of interpretations remain. The currently favoured interpretation advocates a northerly outlet of the Ballarat deep leads and tens of kilometres of post‐basaltic migration of the drainage divide as a result of tectonic warping, drainage disruption by basaltic eruptions and/or river capture. We use detailed data from borehole and mine records to argue that the alternative interpretation, incorporating broad coincidence between the pre‐basaltic and modern divides, is certainly possible and probably more likely. In this interpretation, the Golden Point Lead, the principal and richest deep lead in the Ballarat area, flowed to the south. The best prospects for exploration would therefore be based on persistence of drainage lines rather than drainage rearrangement. The Ballarat goldfield provides an excellent illustration of the ways in which mineral exploration is theory‐dependent, and driven by paradigms.

Orbital Wall Fractures: Evaluation and Management

Over a 49-month period, 121 orbital wall fractures were treated and 92 were followed for a median of 6.5 months (minimum, 3 months). Associated injuries included a 17% incidence of serious globe or optic nerve injuries and 13% incidence of lacrimal drainage disruption. Diplopia occurred in 23% and dystopia in 11%. Management was by observation alone in 14% and exploration in the remainder, with layered gelfilm for defects smaller than 4 cm2, alloplastic sheeting for defects to 6 cm2, and outer cortex of parietal bone for larger dehiscences. There were no decrements in vision from operation, dystopias were corrected to within 2 mm of normal, and diplopia persisted only in those with extraocular muscle paresis. There was no benefit to exploration of orbital wall defects smaller than 2.5 cm2 or with reduction of other midfacial fractures (e.g., malar) when neither dystopia nor entrapment was present, because defects not obturated in such cases had no sequelae.

Basaltic ring structures of the Columbia Plateau

Circular structures, defined by arcuate, concentric ridges and scarps that surround hills, mesas, or crater-like depressions, are localized in an exceptionally thick section of the Roza Member of the Yakima Basalt on the Columbia Plateau. Autointrusive dikes are conspicuous in most ridge segments. Palagonite discovered in a few central hills appears genetically related to the ring structures and suggests an origin involving interaction of water and lava. The dikes intruded a crust about 30 m thick, however, so that substantial cooling must have occurred prior to formation of the rings. A plausible explanation for these unusual features may hinge on the disruption of drainage that occurred as a result of the voluminous basalt extrusion. If, after partial cooling, the molten interior of this thick ponded Roza flow were intersected by a rising ground-water table, rapidly accumulating volatiles could have caused explosive venting as well as doming and cracking of the crust, with concurrent emplacement of granulated sideromelane (later palagonitized) and tephra in craters and fractures. Subsidence of the crust after initial venting could have permitted intrusion of melt into fractures predominantly concentric to the focus of pressure release. Subsequent catastrophic erosion by the Missoula floods effectively removed most of the surficial clues to original structure and morphology, leaving the roots of these enigmatic features partly exposed.

The probable extent of Classical Wisconsin ice in southern and central Alberta

The margin of a former Laurentide ice sheet is traced through southern and central Alberta, from the Saskatchewan border southeast of Medicine Hat to beyond Rocky Mountain House, southwest of Edmonton. This margin, which marks the limit of a significant glacier advance or readvance, is thought to represent the maximum extent of Laurentide ice on the Canadian prairies during Classical Wisconsin time. In the south this margin follows a well-developed hummocky moraine; in the north it is indicated mainly by a discordance in trend of ice-flow markings, a disruption of drainage, and a change in maturity of topography on either side.