Soil Related Factors Controlling Erosion And Landslides In Malaysia

The high temperature and rainfall in Malaysia results in intensive tropical weathering and depending on the parent material, the resultant soil can have deep or shallow soil profiles. Thus, a variety of soils can form with different textures (clay content), structure and porosity. With the high rainfall, soils in steep terrain are subjected to surface erosion when exposed or landslides if the rainwater percolates into the soil profile. Key soil-related factors controlling soil erosion and landslides include local climate, parent material of soils and depth of the weathered profile. Slope and geomorphology, vegetation and land use as well as land management practices also influence erosion and landslides. Measures used to control soil erosion and stabilize slopes require improved understanding of soil weathering, erosion, landslide and their linkages in steep terrain.

Mechanical properties of dense mycelium-bound composites under accelerated tropical weathering conditions

Mycelium, as the root of fungi, is composed of filamentous strands of fine hyphae that bind discrete substrate particles into a block material. With advanced processing, dense mycelium-bound composites (DMCs) resembling commercial particleboards can be formed. However, their mechanical properties and performance under the working conditions of particleboards are unknown. Here, we show how weathering conditions affect the DMC stress and elastic modulus. DMC was made using Ganoderma lucidum mycelium grown on a substrate of sawdust and empty fruit bunch. The DMC was then subjected to weathering under tropical conditions over 35 days and tested under flexural, tensile, and compressive loading with reference to international standards. After exposure to specified weathering conditions, the maximum stress in flexure, tension, and compression decreased substantially. The addition of a protective coating improved the resistance of DMC to weathering conditions; however, the difference between coated and uncoated samples was only found to be statistically significant in tensile strength.

Reconnaissance Of Kenny Hill Formation Outcrops In The Rawang Area, Northern Selangor, Malaysia

New outcrops of Paleozoic meta-sediments northwest of Kuala Lumpur expose the deformational effects of the Late Paleozoic-Mesozoic collisions between various Gondwana-derived continental fragments as they amalgamated to form the core of SE Asia. Over a duration of 6 months, beginning in August 2020, we conducted field trips within northern Selangor to new laterally extensive outcrops for field observations, structural mapping and to measure and log the stratigraphic section. This paper focuses on Upper Paleozoic Kenny Hill Formation outcrops in northern Selangor. The most studied is the heavily weathered Jalan Rawang-Bestari Jaya (JRBJ) outcrop, which is characterised by a steeply dipping (southwest), upward-coarsening succession of sandstones and shales interpreted as a system of ephemeral fluvial channels possibly related to Gondwana glaciation. Concretions within bedding planes and fractures were possibly formed around organic material. Less than 4 km to the east, the Scientex development has excavated fresher outcrops of the same rocks dipping to the NE. Metamorphic lineation is not present in either outcrop location. In addition, a monocline is exposed at outcrop location number 3 nearby. Finally, at Bukit Botak, 14 km to the southwest, a system of westward verging thrust faults, back thrusts and normal faults can be viewed and an angular unconformity or decollement marks the contact between the Upper and Lower Paleozoic. These laterally extensive outcrops are rare and are quickly subject to intense tropical weathering, the encroachment of jungle vegetation and urban development. Historic mapping and prior stratigraphic, structural, and petrographic studies have been conducted in the area, but these relied on poor exposures. As suburban development escalates in the area, we hope that new outcrops, featuring multi-dimensional views of these formations, such as the four described in this paper, will complement the earlier work.

Provenance and Sedimentary Context of Clay Mineralogy in an Evolving Forearc Basin, Upper Cretaceous-Paleogene and Eocene Mudstones, San Joaquin Valley, California

Mudstone samples from the Moreno (Upper Cretaceous-Paleocene) and Kreyenhagen (Eocene) formations are analysed using X-ray diffraction (XRD) and X-ray fluorescence (XRF) to determine their mineralogy. Smectite (Reichweite R0) is the predominant phyllosilicate present, 48% to 71.7% bulk rock mineralogy (excluding carbonate cemented and highly bio siliceous samples) and 70% to 98% of the <2 μm clay fraction. Opal CT and less so cristobalite concentrations cause the main deviations from smectite dominance. Opal A is common only in the Upper Kreyenhagen. In the <2 μm fraction, the Moreno Fm is significantly more smectite-rich than the Kreyenhagen Fm. Smectite in the Moreno Fm was derived from the alteration of volcaniclastic debris from contemporaneous rhyolitic-dacitic magmatic arc volcanism. No tuff is preserved. Smectite in the Kreyenhagen Fm was derived from intense sub-tropical weathering of granitoid-dioritic terrane during the hypothermal period in the early to mid-Eocene; the derivation from local volcanism is unlikely. All samples had chemical indices of alteration (CIA) indicative of intense weathering of source terrane. Ferriferous enrichment and the occurrence of locally common kaolinite are contributory evidence for the intensity of weathering. Low concentration (max. 7.5%) of clinoptilolite in the Lower Kreyenhagen is possibly indicative of more open marine conditions than in the Upper Kreyenhagen. There is no evidence of volumetrically significant silicate diagenesis. The main diagenetic mineralisation is restricted to low-temperature silica phase transitions.

First proofs of preservation of a Mesozoic paleorelief in Southeast Africa: Insights from the (U-Th)/He dating of iron oxides from Malawian duricrusts

&lt;p&gt;Approximately 70% of the emerged relief on the Earth is characterized by erosional low-gradient topography also known as planation surfaces (PS). Many geomorphologists defend the idea that some of these surfaces could be relics of old reliefs uplifted and preserved from erosion for tens of millions years. Some of the highest PS of Southeast Africa (&gt; 2000 m) were considered by King (1962) as remnants of an ante-Cretaceous paleorelief called &amp;#8220;Gondwana Surface&amp;#8221;. Specifically, the Nyika Plateau (Northern Malawi, 2200 m) is one of the largest potential relics of the &amp;#8220;Gondwana Surface&amp;#8221; in Southeastern Africa. This PS overlooks the stripped etchplain of the Malawian Plateau, a potential Late Cretaceous PS about 1200 m of elevation.&lt;/p&gt;&lt;p&gt;However, the preservation of such ancient reliefs is controversial, particularly under a tropical wet-dry climate. Doubts about the ages of these PS exist mainly due to the lack of a precise chronology of these objects on a continental scale. In detail, African PS are often covered by preserved or partly eroded tropical weathering covers such as unconsolidated laterites and/or duricrusts. Under these climatic conditions, lateritic duricrusts can be preserved for millions of years and thus contain several generations of iron oxides witnesses of past local paleoenvironment and geodynamic evolution. In order to understand the formation and preservation of the Southeast African highest PS and date them, we decided to apply (U-Th)/He dating of iron oxides on selected duricrust samples. The exploration of the Nyika Plateau allowed the discovery of an outcropping duricrust and a depositional area of eroded duricrust blocks from different origins. We study duricrust samples from these two areas in order to find some clues about the plateau antiquity and to improve our knowledge about the local paleoclimatic and geodynamic history.&lt;/p&gt;&lt;p&gt;Samples from the in situ duricrust levels, outcropping on the plateau, are polygenic and are formed by three main types of zones: preserved and degraded hematite-rich zones, that are considered to correspond to the initial generation of iron oxides, and a goethitic matrix. The preserved hematites have a Mesozoic (U-Th)/He ages, whereas the goethite-rich matrix of this duricrust formed during the Quaternary. The degraded hematite-rich parts, also rich in quartz, have more dispersed ages ranging from the Mesozoic to the Tertiary. In the detrital accumulation zone, blocks from a similar duricrust were found as well as blocks of another type of duricrusts: a pisolithic one rich in goethite. This last type of duricrust was eroded from a more recent duricrust level, as their iron oxides have Late Tertiary/Quaternary ages. These dating proved the Nyika Plateau relative stability since the Mesozoic period, confirming that duricrusting of reliefs in tropical area can also protect old emerged landscapes from total erosion.&lt;/p&gt;&lt;p&gt;King L.C. (1962) Morphology of Earth, Oliver and Boyld, Edinburg.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;