Deep Sinkholes Research Articles

Dynamics of Greenhouse Gases (CH4 and CO2) in Meromictic Lake Burgsee, Germany

AbstractExtraordinary amounts of greenhouse gases can be stored within the monimolimnion of meromictic lakes, that is, in the water body which is excluded from mixing events. Lake Burgsee (Thuringia, Germany) is a shallow (depth <5 m) lake with a approximately 24 m deep sinkhole, which is fed by underground brine sources and has formed such a monimolimnion. We investigated the carbon dioxide and methane dynamics in this meromictic lake, from production potentials in the sediment via concentrations in the monimolimnion and mixolimnion to emissions to the atmosphere. In the monimolimnion, we found one of the highest methane concentrations (up to >5 mmol L−1) ever reported for a natural freshwater lake, while carbon dioxide concentrations in the water and methane production rates in the sediments were rather ordinary and within the range of holomictic eutrophic lakes. At the thermocline, gas concentrations accumulated to approximately 100 μmol L−1 CH4 and 80–230 μmol L−1 CO2. Estimated fluxes to the atmosphere reached considerable 3.5 mmol CH4 m−2 d−1 and 1.5 mmol CO2 m−2 d−1 above the sinkhole and 0.8 mmol CH4 m−2 d−1 and 0.4 mmol CO2 m−2 d−1 above the near‐by shallow lake center in 2018. Our results demonstrate that lakes in natural brine areas may provide significant storages and releases of greenhouse gases and require further investigation.

Hydrochemistry and water isotopes of a deep sinkhole in north Quintana Roo, Mexico

Sinkholes are common karst forms were we can access the aquifer. This study describes an 85 m deep sinkhole in north Quintana Roo (Mexico), located at 45 km from the coast, allowing us to explore an open section of the aquifer. The profile of the water column was realized to evaluate the physical chemistry, hydrochemistry and water isotopes (δ2H, δ 18O and 3H) in order to distinguish the stratification. It was identified water-rock interaction (limestone) in the upper section (0–40 m), typical from karst groundwater; a mixing zone approximately 10 m thick, and saline intrusion in the deep section (50–80 m). Salinization of the freshwater was observed, likely due to diffusion of sodium and chloride from the deep water. The hydrochemistry suggests seawater intrusion contributing as much a 60% of the water in the deep section. With the stable isotopes, meteoric water, groundwater and seawater mixing was attested. The tritium measurements suggest that the aquifer has short residence time and fast recharge. Few deep sinkholes in Mexico have been studied, the information obtained in Yumkin contributes to the knowledge and understanding of the Yucatan aquifer system.

Hydrochemistry and Water Isotopes of a Deep Sinkhole in North Quintana Roo, Mexico

Hydrochemistry and Water Isotopes of a Deep Sinkhole in North Quintana Roo, Mexico

Hydrology and hydrochemistry of marble aquifer with point recharge from two deep sinkholes, Menderes Massive, western Turkey

Menderes Massive is a NE–SW-trending metamorphic terrain in western Anatolia. The massive is composed of regionally metamorphosed rocks of mica-schist and marble. The Bozdag Mountain is the main horst system in Kucuk Menderes river basin. It is composed of several N-S oriented small horsts and grabens and contains important karst features, such as poljes and sinkholes. Ayvacik and Subatan Poljes are typical closed depressions draining into Ayvacik and Subatan sinkholes (ponors). Both are developed along the N-S directed fault system. The main objective of this study is to determine the karstification and hydrogeochemical features of water circulating in marble terrain and controlled by deep sinkholes in the Bozdag Mountain. Detailed speleological studies demonstrated that the degree of karstification of marble rock depends on the regional tectonic structure, the mineralogy of marble and the water recharge rate into the sinkholes. Tritium isotope and tracer tests indicate very fast flow and connection between Subatan surface water and a spring in lower elevations with high Ca and Mg ion concentration at the south of the study area. Hidrogeologija in hidrokemija marmornega vodonosnika s ponornim tockovnim napajanjem (Masiv Meredes, zahodna Turcija) Masiv Menderes je obmocje metamorfnih kamnin v zahodni Anatoliji, Turcija. Razteza se v smeri SV–JZ in je sestavljeno predvsem iz regionalno metamorfiziranih sljudnih skrilavcev in marmorjev. Goro Bozdag sestavlja sistem manjsih grud in tektonskih jarkov, orientiranih v smeri sever-jug. Masiv je delno zakrasel, s tipicnimi kraskimi oblikami, med katere spadata tudi polji Ayvacik in Subatan, ki se drenirata skozi istoimenske ponore. Obe polji sta razviti v prelomni coni orientirani v smeri sever-jug. Glavni namen opisane raziskave je dolociti stopnjo zakraselosti obmocja in hidrokemicne lastnosti vode, ki tece skozi marmornati masiv. Podrobne speleoloske raziskave so pokazale, da je zakraselost mocno pogojena z regionalno geolosko strukturo, mineralosko sestavo marmorja in velikostjo dotokov v ponore. Izotopske analize tritija in sledenje podzemnih voda kažejo na hiter tok in povezavo med poljem Subatan in visoko mineraliziranimi izviri na jugu obravnavanega obmocja.

A Coastal Yucatan Sinkhole Records Intense Hurricane Events

ABSTRACT Brown, A.L.; Reinhardt, E.G.; van Hengstum, P.J., and Pilarczyk, J.E., 2014. A coastal Yucatan sinkhole records intense hurricane events. The potential of tropical sinkholes as archives for historical hurricane events has yet to be fully explored. This study uses high-resolution (1-cm interval) particle-size analysis to examine two sediment push cores from Laguna Chumkopo, located on the Yucatan Peninsula, Mexico. Core CKC1 (62 cm) was collected from the base of a deep sinkhole located in Laguna Chumkopo at −79.9 m (msl), while the second core, CKC2 (93 cm), was collected from the shallow peripheral margin at −6.4 m (msl). Two coarse fining upward sequences (12 to 35 cm, 46 to 62 cm) in CKC1 had mean particle sizes of approximately 1.5 ϕ (medium sand) with intervening intervals of lime mud (<4 ϕ). Measured 137Cs activity in the bulk sediment (n = 15) and radiocarbon dating (n = 3) using bomb-carbon calibration determined that the lower coarse unit was deposited in the 1960s (after September 1957 ...

Seismic stratigraphy of the Blue Hole (Lighthouse Reef, Belize), a late Holocene climate and storm archive

Abstract Five seismic units may be identified in the ~ 8 m thick Holocene sediment package at the bottom of the Blue Hole, a 120 m deep sinkhole located in the atoll lagoon of Lighthouse Reef, Belize. These units may be correlated with the succession of an existing 5.85-m-long sediment core that reaches back to 1.385 kyrs BP. The identification of seismic units is based on the fact that uniform, fine-grained background sediments show weak reflections while alternating background and coarser-grained event (storm) beds exhibit strong reflections in the seismic profiles. The main source of sediments is the marginal atoll reef and adjacent lagoon area to the east and north. Northeasterly winds and storms transport sediment into the Blue Hole, as seen in the eastward increase in sediment thickness, i.e., the eastward shallowing of the Blue Hole. Previous assumptions of much thicker Holocene sediment packages in the Blue Hole could not be confirmed. So far, close to 6-m-long cores were retrieved from the Blue Hole but the base of the sedimentary succession remains to be recovered. The nature of the basal sediments is unknown but mid-Holocene and possibly older, Pleistocene sinkhole deposits can be expected. The number of event beds identified in the Blue Hole (n = 37) during a 1.385 kyr-long period and the number of cyclones listed in historical databases suggest that only strong hurricanes (categories 4 and 5) left event beds in the Blue Hole sedimentary succession. Storm beds are numerous during 1.3–0.9 kyrs BP and 0.8–0.5 kyrs BP.

Diatom-based paleolimnological reconstruction of regional climate and local land-use change from a protected sinkhole lake in southern Florida, USA

Despite their sensitivity to climate variability, few of the abundant sinkhole lakes of Florida have been the subject of paleolimnological studies to discern patterns of change in aquatic communities and link them to climate drivers. However, deep sinkhole lakes can contain highly resolved paleolimnological records that can be used to track long-term climate variability and its interaction with effects of land-use change. In order to understand how limnological changes were regulated by regional climate variability and further modified by local land-use change in south Florida, we explored diatom assemblage variability over centennial and semi-decadal time scales in an ~11,000-yr and a ~150-yr sediment core extracted from a 21-m deep sinkhole lake, Lake Annie, on the protected property of Archbold Biological Station. We linked variance in diatom assemblage structure to changes in water total phosphorus, color, and pH using diatom-based transfer functions. Reconstructions suggest the sinkhole depression contained a small, acidic, oligotrophic pond ~11000–7000 cal yr BP that gradually deepened to form a humic lake by ~4000 cal yr BP, coinciding with the onset of modern precipitation regimes and the stabilization of sea-level indicated by corresponding palynological records. The lake then contained stable, acidophilous planktonic and benthic algal communities for several thousand years. In the early AD 1900s, that community shifted to one diagnostic of an even lower pH (~5.6), likely resulting from acid precipitation. Further transitions over the past 25 yr reflect recovery from acidification and intensified sensitivity to climate variability caused by enhanced watershed runoff from small drainage ditches dug during the mid-twentieth Century on the surrounding property.

Fracture-controlled fluid circulation and dissolutional weathering in sinkhole-prone carbonate rocks from central Italy

Fractures, karstic cavities, and calcite precipitates are analysed on Mesozoic, carbonate strata from the Cornicolani Mountains, central Italy, to quantify the relationships between fractures and related karstic cavities and to infer the fracture-controlled fluid pathways. The study area is characterized by active sinkholes and other karstic caves, which are among the deepest ones in the world. Results show a clear control of fractures on the process of dissolutional weathering and, therefore, on the fluid circulation. A model is proposed, in which two different modes of dissolutional weathering coexist: (i) a mode of diffuse weathering consisting in the dissolutional enlargement of closely spaced joints and bedding surfaces. This process affects the strata situated at depths of up to 5 m; (ii) a mode of more concentrated weathering active along highly permeable fault damage zones at depths of at least 70 m. These processes are mostly connected with the shallow circulation of calcite-dissolving meteoric waters, and are controlled by the disparity of permeability between the fault damage zones and the surrounding jointed strata. Some calcite precipitates along the studied fault damage zones may be connected with a dissolutional process operated by waters that interacted with the adjacent quiescent volcanic district. Such calcite-dissolving waters and the presence of high-permeable fault damage zones, along which the waters may ascent, are probably the cause for the development of some of the deep sinkholes along faults in the study area.

Sinkhole structure imaging in covered Karst terrain

Ground penetrating radar (GPR) and resistivity techniques have been widely used to map the locations of sinkholes in covered karst terrain. To determine whether a sinkhole is a likely preferential conduit for groundwater flow, however, requires higher‐resolution imaging than that used in conventional sinkhole mapping surveys. Field observations combined with simulated surveys for a 15‐m diameter 3‐m deep sinkhole in west‐central Florida are used to assess the resolution of GPR and resistivity surveys targeting the semiconfining unit that floors the sinkhole depression. 2D resistivity surveys clearly show the central depression as well as resistivity contrasts between the cover sediments within and outside of the sinkhole, but are inadequate for resolving breaches in the semiconfining unit or underlying conduits. A 3D GPR survey resolves vertical structure on the order of tens of centimeters within the semiconfining unit, as well as indicators of conduits that extend several meters beneath the central depression. 3D GPR thus holds promise for imaging hydrologically significant features of sinkholes.

Continental France and Belgium during the early Cretaceous: paleoweatherings and paleolandforms

AbstractDuring the early Cretaceous, successive tectonic phases and several sea level falls resulted in the emersion of the main part of western Europe and the development of thick “lateritic” weathering. This long period of continental evolution ended with the Upper Cretaceous transgressions. During this period, the exposed lands displayed a mosaic of diverse morphologies and weathered landscapes.Bauxites are the most spectacular paleoweathering features, known for long in southern France. Recently, new residual outcrops have been identified, trapped in the karstic depressions of the Grands Causses. Other bauxitic formations, containing gibbsite, have also been recognised, occurring with the Clay-with-Jurassic-cherts in the southeastern border of the Paris Basin. These bauxitic formations overlay Jurassic limestone and are buried beneath Upper Cretaceous marine deposits. The recognition of bauxites up north into the southern Paris Basin significantly widens the extension of the Lower Cretaceous bauxitic paleolandscapes.On the Hercynian basements thick kaolinitic weathering mantles occur. They have been classically ascribed to the Tertiary. The first datings of these in situ paleosoils, by means of paleomagnetism and/or radiogenic isotopes, record especially early Cretaceous ages. This is the case for the “Siderolithic” formations on the edges of the French Massif Central, but also for the kaolinitic profiles in the Belgian Ardennes. In the Flanders, the Brabant basement is deeply kaolinised beneath the Upper Cretaceous cover. These paleosoils show polygenetic evolutions. The relief of these basement paleolandscapes may have been significant. There where probably high scarps (often of tectonic origin) reaching 200 m in elevation or beyond, as well as wide surfaces with inselbergs, as in the present day landscapes of tropical Africa and South America.On the Jurassic limestone platforms occur diverse kaolinitic and ferruginous weathering products. Around the Paris Basin they show various facies, ranging from kaolinitic saprolites to ferricretes. Due to the lack of sedimentary cover, the age of these ferruginous and kaolinitic weathering products has been debated for long, most often allocated to the Siderolithic sensu lato (Eocene-Oligocene). Recent datings by paleomagnetism have enabled to date them (Borne de Fer in eastern Paris Basin) back also to the early Cretaceous (130 ± 10 Ma). These wide limestone plateaus show karstified paleolandforms, such as vast closed and flat depressions broken by conical buttes, but also deep sinkholes in the higher areas of the plateaus and piedmonts. The depth of the karst hollows may be indicative of the range of relative paleoelevations. Dissolution holes display seldom contemporaneous karst fillings, thus implying that the karstland had not a thick weathering cover or that this cover had been stripped off before or by the late Cretaceous transgression. Nevertheless, some areas, especially above chert-bearing Jurassic limestone or marl, show weathering products trapped in the karst features or as a thick weathering mantle.In the Paris Basin, the Wealden gutter looked like a wide floodplain in which fluvio-deltaic sands and clays were deposited and on which paleosoils developed during times of non-deposition. The edges of the gutter were shaped as piedmonts linked up with the upstream basement areas. The rivers flowing down to the plain deposited lobes of coarse fluvial sands and conglomerates. The intensity of the weathering, the thickness of the profiles and their maturation are directly dependent on the duration of the emersion and the topographic location relative to the gutter. Near the axis of the gutter, where emersion was of limited duration, the paleoweathering features are restricted to rubefaction and argillization of the Lower Cretaceous marine formations. On the other hand, on the borders of the basin and on the Hercynian basement, where emersion was of longer duration, the weathering profiles are thicker and more intensively developed.The inventory of the Lower Cretaceous paleoweathering features shows the complexity of the continental history of this period. Moreover, the preserved weathering products are only a part of this long lasting period, all the aspects relative to erosion phases are still more difficult to prove and to quantify. In this domain, apatite fission tracks thermochronology (AFTT) can be helpful to estimate the order of magnitude of denudation. Residual testimonies and subsequent transgressions may enable to estimate relative elevations, but in return, we presently have no reliable tool to estimate absolute paleoelevations. In the work presented here, the inventory enabled to draw a continental paleogeographic map showing the nature of the weathering mantles and the paleolandscape features, just as paleoenvironments and paleobathymetry presently appear on marine paleogeographic maps. For the future, the challenge is to make progress in dating the paleoweathering profiles and especially in the resolution of these datings, in order to correlate precisely the continental records with the different events which trigger them (eustatism, climate, regional and global geodynamics). The final goal will be to build up a stratigraphic scale of the “continental geodynamic and climatic events” in parallel with “sequential stratigraphy” in the marine realm.

Subbottom acoustic and sedimentary records of past surface water?groundwater exchange through sinkhole lakes in south Georgia, U.S.A

Lake Balboa is a deep sinkhole lake in south Georgia. Subbottom acoustic profiling and long sediment cores reveal four stratigraphic units within >20 m of lacustrine fill above acoustically stratified and faulted Miocene/Pliocene overburden and basement Eocene limestone which hosts the Floridan Aquifer system (FAS). Fill consists of thin, rhythmically bedded, peaty sediments (Unit I), indicative of slow sedimentation in a shallow swamp until 13,110–12,680 cal BP, a mix of desiccated and over-consolidated clay and silty sand (Unit II) implying periodic subaerial exposure of the lake bed until 9470–9025 cal BP, and gyttja associated with a rapid 8 m rise in water level by 9120–9020 cal BP (Unit III), as well as an additional rise of 10 m to modern lake levels (Unit IV). Accumulation of nearly 4.5 m of low permeability gyttja, and higher lake levels have fundamentally changed exchange between surface water and groundwater, reducing by 40% or more the rate of vertical leakage to the FAS and increasing shallow aquifer discharge to the lake.

Near real‐time radar interferometry of the Mw 7.1 Hector Mine Earthquake

The Hector Mine Earthquake (Mw 7.1, 16 October 1999) ruptured 45 km of previously mapped and unmapped faults in the Mojave Desert. The ERS‐2 satellite imaged the Mojave Desert on 15 September and again on 20 October, just 4 days after the earthquake. Using a newly‐developed ground station we acquired both passes and were able to form an interferogram within 20 hours of the second overflight. Estimates of slip along the main rupture are 1–2 meters greater than slip derived from geological mapping. The gradient of the interferometric phase reveals an interesting pattern of triggered slip on adjacent faults as well as a 30 mm deep sink hole along Interstate 40.

Probing Bermuda's Lagoons and Reefs: ABSTRACT

Preliminary seismic reflection profiling of Bermuda's lagoons, using the Uniboom system, followed by reconnaissance drilling, has shown that the lowest horizon on the seismic profiles is a strongly reflecting layer, almost horizontal, and with surface roughness of 1 to 3 m. It lies at a depth of about 19 m below sea level near the center of the platform and slopes very gently to 32 m beneath the rim. It appears to be the foundation upon which the rim, reefs, and lagoons have developed, culminating in the present configuration. Above this surface there are Pleistocene reefs, thick End_Page 455------------------------------ sand bodies, and large expanses of lagoonal sediment. The reefs have only a few meters of relief and are commonly draped with lagoonal sediment of unknown age relative to the reefs. The sand bodies are especially common adjacent to the northwest rim and in the southwest lagoon. Drilling has revealed one marine sand body in the northwest, and another, possibly eolian, in the southwest. Lagoonal deposits cover large areas between reefs and sand bodies, and in the northeast, almost the entire area inside the rim. Recent reefs are founded on a variety of substrates. Close to shore they locally fringe the Pleistocene ridges. Over Pleistocene sand bodies in the northwest and southwest, there are prominent reef and sediment shoals. On the rim, reefs encrust whatever Pleistocene rim lies below. However, many lagoon reefs are founded not on topographic highs but on nearly level lagoonal-sediment surfaces, some of which are the lagoonal drapes over Pleistocene reefs. In a few places, recent reefs occur over broad shallow depressions in Pleistocene surfaces. All recent reefs have far greater relief (5 to 20 m) than the buried Pleistocene reefs. Few of the associations and features predicted by the karst origin of atolls hypothesis are present. For example: (1) the rim seems to have built up from the basal reflecting surface, rather than being a solutional modification of it; (2) stacked lagoonal sequences, where slow sedimentation perpetuates a steep-sided solutional depression, are uncommon, and most are present in the enclosed sounds and harbors; (3) many reefs are founded on flat surfaces, not on solutional pinnacles; and (4) deep sink holes are very rare. In general, Bermuda lacks clear signs of being a reef-encrusted paleokarst feature. End_of_Article - Last_Page 456------------

Plankton communities of three Central Florida lakes

A study of planktonic primary productivity and community structure was carried out on three lakes of varying morphometric and chemical features, but which were within a single watershed in Central Florida. Primary productivity in these lakes was evaluated by means of in situ light and dark bottle determinations as well as by calculations based upon chlorophyll and light data. Lake Mize, a deep sinkhole lake containing highly colored waters of low pH, proved to be a very unproductive lake, while Biven's Arm, a shallow-basin lake with alkaline waters and Newnan's lake, a shallow-basin like with highly colored waters both showed relatively high productivities. Phytoplankton components of the two productive lakes were quite similar to one another in being composed of bloom-forming blue-green and green algae, while the predominant forms in Lake Mize were chrysophytes, dinoflagellates and a diatom. Zooplanktonic forms were more uniform among the lakes than were the phytoplankton, though population levels reflected relative productivities among the lakes. Rotifers predominated in the Lake Mize plankton while cladocerans were relatively inabundant. This was opposite to the condition in Biven's Arm and Newnan's Lake. It is suggested that the constant presence of larval Chaoborus in the water column in Lake Mize may be partially responsible for the paucity of cladocera.

A GUIDE TO THE GEOLOGY OF THE DISTRICT ROUND INGLEBOROUGH

I. Introduction and Topography Ingleborough lies near the boundary between two areas of strongly contrasting scenery, the contrast arising from the differences in the rocks involved and the movements they have suffered. The area to the north-east is dominated by the peaks of Whernside ( 7381 )[1][1], Pen-y-Ghent ( 8373 )[1][1], and Ingleborough ( 7474 )[1][1] (2373 ft.). These rise above a broad shelf, about 1300 ft. above O.D., marking the top of a massive limestone, on which have been developed all the features associated with a “karst” cycle of erosion which has reached a mature stage. Extensive limestone pavements with their characteristic “clints” and “grikes” (Pl. 4), deep sink-holes, such as Gaping Gill ( 751727 ) and swallow holes like Hull Pot ( 823746 , Pl 9, Fig. 1), caves with a wealth of stalactites and stalagmites such as Clapham Cave ( 754711 ) and White Scar Cavern ( 713746 ), natural bridges such as God’s Bridge ( 733764 ) and collapsed caves such as Trow Gill ( 755717 ), all show the solvent action of the disappearing surface water. According to Miss Sweeting (1950), the 1300 ft. shelf is an old erosion surface and an upper series of caves at about 1250 ft. were produced at a time when the water-table lay just below that surface. A lower series of caves at 950 to 1000 ft. belong to a water-table position associated with a rejuvenation stage of the river system while the lowest system of caves belong to the present cycle. The course of the underground drainage was investigated by members of our Society in collaboration … [1]: #fn-1

Late Recent History of Cote Blanche Salt Dome, St. Mary Parish, Louisiana

One of the clearest examples of solution of the salt in the Gulf Coast is given in the late Recent history of Cote Blanche. Prior to the uplift of the present topographic mound, solution (of two salt spines?) produced two deep sink-holes, in which great thickness of late Recent alluvium accumulated. One of the sink-holes was uplifted to form the crest of the present topographic mound and shows no effects of subsequent solution. The activity of solution under the other sink-hole continued after the uplift of the present topographic mound, possibly to the present. Formation of residual cap rock is not recognized, but is not precluded.