One of Venus' most enigmatic landforms is Baltis Vallis, the longest channel on the surface (∼7,000 km long). We identify a possible mid‐channel island that implies a south to north flow direction ...during formation. However, since the flow direction of Baltis Vallis is otherwise not well constrained, we analyze topographic conformity in both flow directions. In either case, topography appears to be altered across most analyzed wavelengths after the formation of Baltis Vallis. Fourier analysis shows two ranges of prominent wavelengths, 225 ± 15 km and ∼3,500 ± 1,200 km. The shorter wavelengths correspond to deformation belts that cross Venus' low plains. The longest is plausibly associated with the dynamic uplift wavelength of the crust by mantle plumes, but is less robustly detected. Higher resolution observations provided by the VERITAS and EnVision missions can help resolve the source location of Baltis Vallis and constrain if the longest wavelength postdated the canale's formation.
Plain Language Summary
Venus' surface is covered in a plethora of strange landforms, at least from the perspective of Earth. One of the longest is an about 7,000 km channel named Baltis Vallis, comparable to the Amazon and Nile rivers, but instead likely formed by volcanic processes. Baltis Vallis serves as a unique opportunity on Venus due to its length. The channel recorded surface altering processes in its topography, but we first check if the channel retained topographic information from when it initially formed. Our test shows that the topography has been altered by later processes and those processes should dominate the signal in analysis of the current topography. That analysis shows 2 length‐scales are overrepresented in the topography. The shorter length‐scale correspond to thin mountain range‐like features that cross Venus' low plains. The longest wavelength is plausibly associated with uplift of the crust by mantle plumes and this value will be useful when creating models of Venus' interior.
Key Points
A possible mid‐channel island in the longest channel on Venus implies a south to north flow direction
We show that the topography and morphology of this channel was modified along most of its length
Fourier analysis of the channel's topography shows a group of prominent wavelengths at ∼210–240 km, that we link to deformation belts
Gunungapi Purba Soreang yang terletak di Kabupaten Bandung merupakan gunungapi yang tidak aktif dan tererosi kuat. Daerah ini memperlihatkan susunan litologi gunungapi strato-vulanik serta memiliki ...morfologi perbukitan bergelombang tak beraturan dan bukit-bukit soliter. Penelitian ini dilaksanakan untuk mengetahui hubungan geomorfologi dan geologi Gunungapi Purba Soreang dengan potensi keberadaan cebakan emas. Metode yang dilakukan adalah analisis geomorfologi, pemetaan vulkanostratigrafi dan analisis struktur geologi serta identifikasi zona alterasi dan mineralisasi. Berdasarkan peta morfografi dan kemiringan lereng, daerah penelitian menunjukan bentuk bentang alam khas gunungapi berupa bentuk yang menyerupai lingkaran atau circular feature yang dihasilkan oleh batuan intrusi, kubah lava, dan leher gunungapi purba, sebagai petunjuk lokasi sumber erupsi. Produk gunungapi purba Soreang memperlihatkan fasies sentral hingga distal dalam beberapa satuan gumuk dan khuluk. Litologi penyusun daerah ini di antaranya intrusi andesit dan diorit yang sebagian besar telah mengalami alterasi hidrotermal, perselingan lava dan breksi piroklastika dan tuff. Litologi ini menunjukkan bahwa Gunungapi Soreang merupakan jenis strato-vulanik. Di area Gunungapi Purba Soreang ini telah dilakukam eksplorasi potensi mineralisasi emas pada zona sentral. Pertambangan tradisional juga telah dilakukan oleh masyarakat lokal. Berdasarkan analisis terpadu bentang alam dengan litologi, perkiraan tubuh Gunungapi Purba Soreang dan zona sentral gunungapi tersebut dapat diidentifikasi. Hasil identifikasi tersebut digunakan untuk membantu penetapan area eksplorasi potensi cebakan emas di wilayah Soreang.
The comments raised by Paumard et al. (2020) led us to identify some pitfalls and limitations regarding the use of seismic geomorphology and seismic stratigraphy for paleoenvironmental ...reconstructions of carbonate systems and to add some clarifications on the Teillet et al. (2020a) depositional model. The comparison of the paleoenvironmental predictions by Paumard et al. (2017) with core data revealed severe inconsistencies which are due to the diachronous nature of the seismic horizon from which attribute map was computed and to the omission of fluid effects on seismic expression. In addition, detailed well-to-seismic ties revealed also that chronostratigraphic well-correlations using seismic data should be considered with caution when vertical seismic resolution is reduced (>20 m). Regarding the development pattern of the Yadana platform, we consider that the platform backstepping evidenced from seismic is not is in contradiction with the lack of deepening upward trend on platform top revealed by cores. The existence of a euphotic carbonate factory in Yadana cannot be ruled out. From the available dataset such a putative carbonate production would be reduced and/or exported out of the western Yadana platform. Finally, we propose a general workflow for better integrating seismic reflection patterns and attributes in the paleoenvironmental reconstruction of strongly diagenetized carbonate reservoirs which are imaged by low to moderate resolution (>20 m) seismic datasets.
•Core to seismic-tie shows the invalidity of the seismic-based paleoenvironmental reconstructions by Paumard et al., 2017.•Core calibration is needed, in buried and strongly diagenetized carbonate reservoirs with variable fluid content.•Apparent lithostratigraphic correlations are the consequence of changing paleoceanographic conditions through times.•Yadana platform backstepping is not in contradiction with the lack of deepening upward trend evidenced from cores.•A workflow of 3D paleoenvironmental reconstructions integrating cores and well-logs and seismic geomorphology is proposed.
The Ciciriello catchment is a 3 km2 drainage sub-basin of the Bussento river basin, located in the southern part of the Campania Region (Southern Italy). Since 2012, this catchment has been studied ...using an interdisciplinary approach—geomorphological, hydrogeological, and hydrological—and a hydro-chemical monitoring system. Following previous research, the aim of this paper is to calibrate, on this catchment, the hydrologic parameters for a water budget at event time-scales using the HEC-HMS model, adopting object-based hydro-geomorphological class features. Firstly, lumped modeling was performed to calibrate the hydrologic parameters from 20 observed hydrographs at the downstream monitoring station of the Ciciriello catchment. Then, physical-based rainfall–runoff modeling was conducted using three different procedures: (1) applying the recession coefficients to each outlet with a newly defined hydro-geomorphologic index (HGmI); (2) assessing the storage coefficient for each sub-basin as a weighted mean of HGmI; and (3) using the storage coefficient associated with the largest HGmI in the sub-basin. The adopted procedures were tested using diverse goodness-of-fit indices, resulting in good performance when the object-based hydro-geomorphotypes were used for the parameter calibration. The adopted procedure can thus contribute to improvements in rainfall–runoff and water budget modeling in similar ungauged catchments in Mediterranean, hilly, and forested landscapes.
We describe a new set of data structures and algorithms for dynamic terrain modeling using a triangulated irregular network (TINs). The framework provides an efficient method for storing, accessing, ...and updating a Delaunay triangulation and its associated Voronoi diagram. The basic data structure consists of three interconnected data objects: triangles, nodes, and directed edges. Encapsulating each of these geometric elements within a data object makes it possible to essentially decouple the TIN representation from the modeling applications that make use of it. Both the triangulation and its corresponding Voronoi diagram can be rapidly retrieved or updated, making these methods well suited to adaptive remeshing schemes. We develop a set of algorithms for defining drainage networks and identifying closed depressions (e.g., lakes) for hydrologic and geomorphic modeling applications. We also outline simple numerical algorithms for solving network routing and 2D transport equations within the TIN framework. The methods are illustrated with two example applications, a landscape evolution model and a distributed rainfall-runoff model.
GEOGRAPHICAL STUDIES WITH EMPHASIS
ON GEOMORPHOLOGY: THEORETICAL, METHODOLOGICAL,
MAPPINGS AND APPLICATIONS IN ENVIRONMENTAL
STUDIES. The analyses and the geomorphological mapping
are important tools ...for research of the relief and for its spatial
relationships, allowing approaches to geographic interest as
the potentiality and susceptibility of resources of the relief
face of different forms of ownership of earth surface by the
society. The forms of relief are created by endogenous and
exogenous processes by which correspond to areas of erosion
and accumulation as well as the areas created by men.
Furthermore, a classification of relief passes through the
notion to express it cartographically based on concepts of
morphostructure for larger units, and morphosculture to the
forms of relief contained in each existing morphostructure.
The urban interventions are important elements for the
characterization of new geomorphological processes
generated from human activities. For the implementation of
analylses and geomorphological mapping, the steps are: (1)
analysis of geological and tectonics charts; (2) analysis of
topographic maps and development of thematic maps
(morphometric maps, topographic profiles and terrain
models) through geoprocessing; (3) development of map of
relief elements from remote sensors in a historical period that
allows the recognition of features of relief with their
morphological features virtually unique and, from recent
remote sensing, the identification of changes in the original
morphology; (4) surveying field, including (5) collection of
materials for subsequently laboratory analysis. The
geomorphological map refers to a cartographic product of
synthesis. Its construction is based on all documents
described above, activities in the field and on the results of
the analysis conducted in the laboratory. In addition to these
procedures, information obtained from the literature review
undertaken in connection with regional geological and
geomorphological framework, and the process of occupation
and possession of natural elements are also relevant.
A análise e o mapeamento geomorfológico são importantes
instrumentos de pesquisa do relevo e de suas relações
espaciais, permitindo abordagens de interesse geográfico
como a potencialidade e a suscetibilidade dos recursos do
relevo frente às diferentes formas de apropriação da
superfície terrestre pela sociedade. As formas de relevo são
criadas por processos endógenos e por processos exógenos,
que correspondem às superfícies de erosão e acumulação e às
superfícies criadas pelos homens. Com isso, uma classificação
de relevo passa pela concepção de se expressar
cartograficamente o relevo baseada na conceituação de
morfoestrutura, para as unidades maiores, e de
morfoescultura para as formas de relevo contidas em cada
morfoestrutura existente. As interferências urbanas são
elementos importantes para a caracterização dos novos
processos geomorfológicos gerados a partir das atividades
humanas. Para execução da análise e do mapeamento
geomorfológic, as etapas são: (i) análise das cartas geológicas
e tectônicas; (ii) análise da carta topográfica e elaboração de
mapas temáticos (mapas morfométricos, perfis topográficos e
modelos do terreno) através do geoprocessamento; (iii)
elaboração de mapa de elementos do relevo a partir de
sensores remotos de um em período histórico que permita a
identificação das feições de relevo com suas características
morfológicas praticamente originais e, a partir de sensores
remotos recentes, a identificação das alterações na
morfologia original e (iv) levantamento de campo, incluindo
(v) coleta de materiais para posterior análise laboratorial. O
mapa geomorfológico refere-se a um produto cartográfico de
síntese. Sua construção apóia-se em todos os documentos
anteriormente descritos, nas atividades de campo e nos
resultados das análises realizadas em laboratório. Além
desses procedimentos, também são relevantes as informações
obtidas a partir da revisão bibliográfica realizada no contexto
geológico e geomorfológico regional, bem como do processo
de ocupação e de apropriação dos elementos naturais.
ESTUDIOS GEOGRÁFICOS CON ÉNFASIS EN LA
GEOMORFOLOGÍA: CUESTIONES TEÓRICAS,
METODOLÓGICAS, RELEVAMIENTO Y APLICACIONES EN
ESTUDIOS AMBIENTALES. El análisis y el relevamiento
geomorfológico son importantes instrumentos de pesquisa
del relieve y de sus relaciones espaciales, permitiendo
enfoques de interés geográfico como la potencialidad y la
susceptibilidad de los recursos del relieve frente a las
diferentes formas de apropiación de la superficie terrestre
por la sociedad. Las formas de relieve son creadas por
procesos endógenos y por procesos exógenos, que
corresponden a las superficies de erosión y acumulación y a
las superficies creadas por los hombres. Con eso, una
clasificación de relieve pasa por la concepción de expresarse
cartográficamente el relieve basada en la conceptuación de
morfoestructura, para las unidades mayores, y de
morfoescultura para las formas de relieve contenidas en cada
morfoestructura existente. Las interferencias urbanas son
elementos importantes para la caracterización de los nuevos
procesos geomorfológicos generados a partir de las
actividades humanas. Para ejecución del análisis y del
relevamiento geomorfológicos, las etapas son: (i) análisis de
las cartas geológicas y tectónicas; (ii) análisis de la carta
topográfica y elaboración de mapas temáticos (mapas
morfométricos, perfiles topográficos y modelos del terreno) a
través del geoprocesamiento; (iii) elaboración de mapa de
elementos del relieve a partir de sensores remotos de uno
periodo histórico que permita la identificación de los aspectos
de relieve con sus características morfológicas prácticamente
originales y, a partir de sensores remotos recientes, la
identificación de las alteraciones en la morfología original, y
(iv) campaña de campo, incluyendo (v) recolecta de
materiales para posterior análisis laboratorial. El mapa
geomorfológico se refiere a un producto cartográfico de
síntesis. Su construcción se apoya en todos los documentos
anteriormente descriptos, en las actividades de campo y en
los resultados de los análisis realizados en laboratorio.
Además de esos procedimientos, también son relevantes las
informaciones obtenidas a partir de la revisión bibliográfica
realizada en el contexto geológico y geomorfológico regional,
así como del proceso de ocupación y de apropiación de los
elementos naturales.
Karsts and paleokarsts of the Mlalet basin (Cévennes, Gard, France) : formation and morphological evolution of an ancient karst cut by topographical surface. The Mialet basin is a limestone massif of ...62 km2 on the edge of the Cévennes Mountains, made of 400 m of limestones and dolomites. Two allochtonous rivers (Gardons) cross and dissect it. Many caves are to be found at each level and their formation cannot be explained with today's topography. Surface karstic features (dolines) are rare but karstic fillings and many speleothems can be observed on the surface. These deposits are former karst (paleokarst) cut by rivers incision. Recent karstic systems are organized differently but new subterranean circulations sometimes flow in old galleries and declog them.
Le bassin de Mialet est un massif calcaire de 62 km2 appartenant à la bordure cévenole. Les phénomènes karstiques de surface sont rares, en revanche l'endokarst est bien développé et de nombreuses cavités de section importante existent à toutes altitudes qui débouchent à flanc de versant. La présence de poches de sédiments endokarstiques et l'abondance des massifs stalagmitiques exhumés confirment l'idée d'anciens systèmes karstiques démantelés. L'étude des cavités principales (grotte de Trabuc, évent de la Vernière) et de tronçons de galeries isolés, permet de proposer une évolution d'ensemble pour ces cavités. Le système majeur, formé en zone noyée profonde et peut-être sous couverture (marnes liasiques), a ensuite subi un comblement généralisé qui affecte toutes les cavités du secteur, quelle que soit leur altitude. L'incision des vallées provoque ensuite une réouverture du système. Certaines galeries sont réutilisées et partiellement vidées de leurs remplissages. Parallèlement, un nouveau système karstique se met en place, morphologiquement très différent du précédent, et en rapport avec la topographie commandée par l'enfoncement des Gardons. Au fur et à mesure de la dissection du massif, les galeries réutilisées sont de nouveau fossilisées et un important comblement calcitique s'y développe. Le recul des versants recoupe ces galeries et leurs remplissages affleurent en surface. Plusieurs traçages chimiques ont montré qu'il existe toujours une connexion hydrogéologique entre ces vieux tronçons et le niveau des circulations actuelles.
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