scholarly journals Smoganica – a Cave Developed in Upper Cretaceous Breccia

2016 ◽  
Vol 34 (2) ◽  
Author(s):  
Martin Knez ◽  
Tadej Slabe ◽  
Stanka Šebela
Keyword(s):  
Sea Level ◽  
Upper Cretaceous ◽  
Coarse Grained ◽  
Water Stream ◽  
Cave Sediments ◽  
Limestone Breccia

 Na planoti Banjšice (SZ Slovenija) je najdaljša izvirna jama Smoganica, dolga 492 m. Jama (na nadmorski višini 505 m) leži na jugozahodnem pobočju Čukle (770 m) vzhodno od reke Soče (153 m nad morjem). Smoganica se je razvila v apnenčevi breči, ki je tu debela 10 m in je del zgornjekrednih flišnih plasti. V okolici jame so zeleni laporji kot vključki v breči ali pa je breča vključena v plasti zelenega laporja. Klasti v debelozrnati breči, v kateri je tudi jama, merijo od nekaj cm do več dm v premeru. Klasti večinoma izvirajo iz mlajših rudistnih apnencev, spodnje in zgornje krede ter jurskih mikritnih in oolitnih apnencev. Jama Smoganica leži okrog 2 km južno od Idrijskega preloma in okrog 200 m severno od Kobariškega preloma. V jami zasledimo dve glavni razpoklinski smeri: N30-45°E in N120-135°E. Smoganica se je oblikovala kot sistem manjših rovov, ki so se razvili znotraj breče v vseh smereh. Jama je nastala v freatičnih razmerah. Kasneje je bila v celoti zapolnjena s sedimenti, nad katerimi so nastale nadsedimentne skalne oblike. Sedimenti so bili nato iz jame odnešeni. Današnji vodni tok oblikuje dno jamskih rovov. Višje vode oblikujejo fasete in draslje, nižje pa talne žlebove. Jamo lahko opredelimo kot poligenetsko, saj je njene dele že povsem preoblikovala voda, ki prenika s površja in polzi po jamskih stenah. On the Banjšice plateau (NW Slovenia) the longest spring cave is 492 m long Smoganica. The cave (505 m above sea level) is situated on the SW slope of Čukla (770 m) E from the Soča river (153 m above the sea level). Smoganica is developed in limestone breccia, which is 10 m thick and belongs to the Upper Cretaceous flyschrocks. On the territory around the cave, the green marls are included in breccias or breccias are included into the green marls. Clasts in coarse-grained breccia, in which the cave is located, vary from some cm to several dm in diameter. Clasts are mostly deriving from younger rudist limestones, Lower and Upper Cretaceous and Jurassic micritic and oolitic limestones. Smoganica is situated about 2 km south from Idrija fault and about 200 m north from Kobarid fault. There are two principal fissure orientations in the cave, N30-45ºE and N120-135ºE. Smoganica was formed from the system of smaller passages that have been developed inside the breccia in 3D. The cave was formed in phreatic conditions, later it was completely filled with cave sediments.In the next stagethe above-sediment rock forms were developed. Cave sediments were later removed from the cave. Today the active water stream is cutting rock forms in the bottom of the cave passages. Higher water quantities are forming scallops and potholes and lower quantities floorchannels. Smoganica can be described as polygenetic cave because the percolating water is reshaping the passages.

scholarly journals Speleogenesis and depositional hystory of paleokarst phreatic caves/cavities; Podgrad, SW Slovenia

2021 ◽  
Author(s):  
Bojan Otoničar
Keyword(s):  
Host Rock ◽  
Upper Cretaceous ◽  
Coarse Grained ◽  
Mixing Zone ◽  
Carbonate Sediment ◽  
Lower Eocene ◽  
The Third ◽  
Cave Sediments ◽  
Upper Paleocene ◽  
Δ13c And Δ18o

The studied palaeokarst corresponds to an uplifted peripheral foreland bulge when Upper Cretaceous diagenetically immature eugenetic carbonates were subaerially exposed, karstified and subsequently overlain by upper Paleocene/lower Eocene palustrine limestone. Among the subsurface paleokarstic features, both vadose and phreatic forms occur.  The phreatic caves/cavities include features characteristic of the mixing zone speleogenesis at the interface between freshwater (brackish water) lenses and the underlying seawater. They were found in various positions with respect to the paleokarstic surface, the deepest being about 75 m below the surface. Three indistinct horizons of cavities/caves and intermediate vugs were recognized. Subsequently, all cavities were completely filled with detrital sediments and speleothems in the phreatic and vadose zones. In general, the phreatic cavities of the lower two horizons are geopetally filled with mudstone derived from incomplete dissolution of the host rock and overlain by coarse-grained, blocky calcite. Shallower below the paleokarst surface, a large phreatic cave of the third horizon is filled with flowstone overlain by reddish micritic carbonate sediment with intercalated calcite rafts. In the upper part of the cave, sediments derived from the paleokarst surface are gradually becoming more abundant. Vadose channels, which may also intersect the cave sediments, are mainly filled with "pedogenic" material derived from the paleokarst surface. Immediately prior to marine transgression over the paleokarst surface, some cavities were filled with marine-derived microturbidites. In general, the diversity of cave fills and the amount of surface material decrease with distance from the paleokarst surface. Below the paleokarst surface, the δ13C and δ18O values of a host rock and cavity deposits show good correlation with trends significant for meteoric diagenesis. It is shown that deposits associated with phreatic caves can be of great importance for the study of the speleogenetic, geomorphological and hydrogeological evolution of certain palaeokarst regions.

Lateral and vertical facies sequences in the Upper Cretaceous Chungo Member, Wapiabi Formation, southern Alberta

1987 ◽  
Vol 24 (4) ◽  
pp. 771-783 ◽  
Author(s):  
Lorne R. P. Rosenthal ◽  
Roger G. Walker
Keyword(s):  
Sea Level ◽  
Upper Cretaceous ◽  
Fluvial Deposits ◽  
Southern Alberta ◽  
Surface Marking ◽  
Shoreline Progradation ◽  
Erosion Surface

The Chungo Member of the Wapiabi Formation (Campanian) shales out northward and (or) eastward from Lundbreck to the Bow Valley, southern Alberta. At Lundbreck, basinal mudstones are overlain by turbidite and hummocky cross-stratified sandstones in an overall coarsening-upward sequence. The marine part of the sequence is capped by dominantly swaley cross-stratified sandstones, interpreted as storm-dominated shoreface deposits. Nonmarine fluvial deposits overlie the shoreface. Essentially the same sequence persists northward to the area of the Highwood River, but in the Highwood River – Sheep River – Longview area, the swaley cross-stratified shoreface sandstones are progressively cut out by a north- and (or) east-ward-dipping erosion surface with up to 40 m of relief. The erosion surface is overlain by a lag of chert pebbles and then by a marine coarsening-upward sequence of offshore to shoreface deposits (the lower tongue of the Nomad Member). Nonmarine Chungo deposits then prograded north- and (or) eastward to overlie this marine tongue in the Highwood area. They are in turn abruptly overlain by a gravel-coated transgressive surface marking the upper marine tongue of the Nomad Member. Finally, marine shales of the Nomad Member are abruptly overlain by dominantly fluvial rocks of the Belly River Formation.We suggest that the main Chungo shoreface, stratigraphically equivalent to the Milk River sandstone of southeastern Alberta, prograded north- and (or) eastward to at least the Highwood River area. A rapid relative lowering of sea level followed by stillstand resulted in the formation of the erosion surface and the supply of gravel to the basin. The overlying coarsening-upward sequence indicates the resumption of shoreline progradation, but this appears to have been relatively short-lived; it was terminated by the transgression of the upper Nomad tongue.

scholarly journals High-frequency sea-level changes recorded in deep-water carbonates of the Upper Cretaceous Dol Formation (island of Brač, Croatia)

2010 ◽  
Vol 61 (1) ◽  
pp. 29-38
Author(s):  
Damir Bucković ◽  
Maja Martinuš ◽  
Duje Kukoč ◽  
Blanka Tešović ◽  
Ivan Gušić
Keyword(s):  
Sea Level ◽  
Deep Water ◽  
High Frequency ◽  
Upper Cretaceous ◽  
Distal Part ◽  
Preferential Orientation ◽  
Sea Level Changes ◽  
Carbonate Production ◽  
Fine Grained ◽  
Platform Margin

High-frequency sea-level changes recorded in deep-water carbonates of the Upper Cretaceous Dol Formation (island of Brač, Croatia)The upper part of the Middle Coniacian/Santonian-Middle Campanian deep-water Dol Formation of the island of Brač is composed of countless fine-grained allodapic intercalations deposited in an intraplatform trough. Within the studied section 13 beds can be distinguished, each defined by its lower part built up of dark grey limestone with abundance of branched, horizontally to subhorizontally oriented burrows, and the upper part, in which the light grey to white limestone contains larger burrows, rarely branched, showing no preferential orientation. The lower, dark grey, intensively bioturbated levels are interpreted as intervals formed during high-frequency sea-level highstands, while the upper, light grey-to-white levels are interpreted as intervals formed during the high-frequency sea-level lowstands. Cyclic alternation of these two intervals within the fine-grained allodapic beds is interpreted as the interaction between the amount of carbonate production on the platform margin and the periodicity and intensity of shedding and deposition in the distal part of toe-of-slope environment, which is governed by Milankovitch-band high frequency sea-level changes.

DETERMINING RESERVOIR CONTINUITY IN THE LAMINARIA FORMATION BY INTEGRATED GEOLOGICAL STUDY

2001 ◽  
Vol 41 (1) ◽  
pp. 415 ◽  
Author(s):  
D.C. Barr ◽  
A.F. Kennaird ◽  
J. Fowles ◽  
N.G. Marshall ◽  
V.L. Cutten
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
Sea Level ◽  
Clay Content ◽  
Coarse Grained ◽  
Log Data ◽  
Reservoir Performance ◽  
Subaqueous Dunes ◽  
Reservoir Sandstones ◽  
Reservoir Potential

A recent geological study, integrating sedimentological core-derived descriptions with ichnofacies, high resolution biostratigraphy and wireline log data, establishes the lateral continuity of reservoir sandstones in the Laminaria Formation. By defining a hierarchy of bedding surfaces and correlating this hierarchy with major correlation surfaces, and lateral and vertical facies patterns, it was possible to identify genetically related sediment packages between 12 wells in the study area.The Laminaria Formation is interpreted to have been deposited on a tide and storm-influenced marine shelf, and was strongly influenced by fluctuations in sea level. The formation consists of a series of progradational parasequences, each dominated by good quality, fine- to medium-grained sandstone. These sandstones are believed to have formed as subaqueous dunes or sand banks, exhibiting blanket-like geometry over much of the area. Several sandstones are capped by thin, intraclast-rich layers that mark transgressive surfaces of erosion. These surfaces can be traced across the study area and, therefore, act as important correlative markers.Evidence of gradual transgression, which ultimately led to the drowning of the system, is seen near the top of the formation. Clay content increases upward, while grain size and bedding thickness generally decrease. However, several thin, laterally extensive, medium- to coarse-grained sandstones exist, improving reservoir potential in this part of the formation.The results of this study are being used to estimate reserves and assess reservoir performance, and will serve as a basis for future geological and petrophysical modelling work.

Very coarse-grained beaches as a response to generalized sea level drops in a complex active tectonic setting: Pleistocene marine terraces at the Cadiz coast, SW Spain

2016 ◽  
Vol 382 ◽  
pp. 92-110 ◽  
Author(s):  
Laura González-Acebrón ◽  
Ramón Mas ◽  
José Arribas ◽  
Jose Manuel Gutiérrez-Mas ◽  
Carlos Pérez-Garrido
Keyword(s):  
Sea Level ◽  
Tectonic Setting ◽  
Coarse Grained ◽  
Sw Spain ◽  
Marine Terraces ◽  
Active Tectonic
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