I recently had the idea of reconstructing a depositional history of my cave fill using magnetostratigraphy. I contacted Dr. Reynolds at Brevard U. who formally ran an LLC conducting such work, but he no longer has the time to run it as a business. He told me to contact Dr. Sasowsky at Akron. Sasowsky is an expert in karst and cave fill and was able to speak to me over the phone about cave fill magnetostratigraphy.
The technique is usually carried out on sediments or rocks younger than Mid Jurassic so they can be compared to the Geomagnetic Polarity Time Scale (GPTS) which has been constructed from the measurements of ocean floor polarity, hence the Mid Jurassic time constraint. However, some work has been done on older rocks and a complete global scale is slowly being built. Analyses on the Cherokee Series has not been completed, so there is nothing to compare my cave fills to if the work was to be done. However, the technique could still be used to compare the polarities between outcrops, to see if they were deposited at the same time or if the deposition overlapped at all.
But there is another hitch to this type of work. The older the rocks are the harder it is to get reliable data. This is due to new polarities being recorded when fluids move through the rocks. Measurements of 3 or 4 polarities would not be uncommon for cave fills of this age and their reliability for use as global comparisons is unlikely. The polarities could still be correlated between cave fills.
Magnetostratigraphy is difficult work to both conduct and analyze. Therefore, getting U. of Michigan (where Sasowsky has his work done) or any other lab to conduct these tests is very doubtful. The number of labs which actually do this is dwindling on account of its difficulties. The Slovenians (the birthplace of karst science) are the only ones who conduct cave fill magnetostrat on rocks this old.
Monday, February 22, 2010
Thursday, February 18, 2010
References
I have been so busy gathering references that I have been neglecting my blog. I have 30+ now so it's time to deleneate the more useful papers.
Before I get into the more specific papers on my topic of clastic cave-fills, I think it's important to first cite the big dogs, and since caves are the ultimate product of unconformities, what better paper to cite than Sloss (1963). This is the paper that first described the earth's major transgressive/regressive tracts and put them into global context; many now refer to them as Sloss Sequences. The major sequence in which these paleocaverns were formed during is the Kaskaskian. If you are a geologist than this classic paper is a must-read.
The next major citation I have is a collection of articles in a book known simply as Paleokarst (1988), edited by N.P. James and P.W. Choquette. The introduction, written by the editors, makes for an excellent citation on basic karst morphology and processes. Within the book are articles by some of the modern pioneers on karst: Derek Ford and Charles Kerans. Including the intro, this collection has 19 articles which will be more than enough to cover the basics of karstification.
Since I am wanting to explore the hydrocarbon reservoir potential of these paleocaverns, I also collected references on karst reservoirs. C. Kerans' 1988 paper in the AAPG Bulletin titled Karst-Controlled Reservoir Heterogeneity is an excellent paper to start with.
A few other references I have collected are:
Evans, J. E. R. J. M. (2006). "Pennsylvanian fluvial cave sediments in the Mississippian Leadville Limestone, southwestern Colorado, U.S.A." Mountain Geologist 43(4): 283-297.
In southwestern Colorado, paleokarst of the Mississippian Leadville Limestone contains fluvial cave sediments, debrites, and fissure-fill sediments. The fluvial cave sediments form fining-upward sequences consisting of: 1) clast-supported, pebble-cobble conglomerate composed of limestone and chert clasts and siltstone intraclasts (lithofacies Gm), 2) massive sandy siltstone which may show primary current lineation (lithofacies SSm), 3) laminated siltstone-mudstone rhythmites (lithofacies Fl), and 4) massive silty mudstones (lithofacies Fm). The sequences commonly terminate with an upper mudcracked claystone drape (lithofacies Fcd). Some silty sandstone with climbing ripple lamination (lithofacies Sr) is observed. The fluvial cave sediments are interpreted as ephemeral, high-energy, flood-flow deposits (inundites) that flowed through open-framework phreatic tubes. The inundites are interbedded with debrites, speleothems, and karst-collapse breccias. The fluvial sediments are texturally and compositionally identical to the overlying Pennsylvanian Molas Formation, which has recently been reinterpreted as a loessite (eolian siltstone). The allochthonous paleocave sediments are interbedded with parautochthonous cave sediments (chaotic, mosaic, and crackle breccias) and with autochthonous cave sediments (speleothems). Observed speleothems include flowstone, dripstone, and cave pearls. Some of the inundite events were sufficiently energetic to erode and transport fragments of speleothems. Exposures of Leadville paleokarst demonstrate that: 1) phreatic tubes formed by subsurface erosion below the water-table; 2) the tubes were partially to completely filled by fluvial cave sediments; 3) individual phreatic tubes subsequently collapsed to form breakout domes (upward-widening domal structures made from karst breccias); and 4) the breakout domes were subsequently infilled by translocated loess infilling fissures and breccia matrix, speleothem formation, and multiple episodes of cementation. A vertical sequence of phreatic tubes and superimposed breakout domes suggests that regional paleogroundwater surfaces were falling during the early Pennsylvanian. This may have been controlled by the downcutting of adjacent solution valleys and/or by paleoclimate change.
Madeyska, T. C. K. (2002). "Cave fillings - A chronicle of the past. An outline of the Younger Pleistocene cave sediments study in Poland." Acta Geologica Polonica special 52(12): 75-95.
The scientific exploration of Polish cave sediments started 130 years ago. Important Palaeolithic sites were discovered and investigated from that time by archaeologists and zoologists. During the second half of the 20th century geological analysis was introduced to the cave filling study. More than 50 caves and rock shelters, differentiated according to their shape and dimensions, have been explored to date, every one of which contained subfossil animal remains. In about 30 sites, culture layers, scattered artefacts or other traces of the activity of Palaeolithic people were found. The sedimentary successions, 2-8 metres thick, consist mainly of elastic components that reflect the past climatic changes. The subfossil fauna includes animals living in tundra, steppe, forest and aquatic environments. The proportions of particular groups vary with the position in the succession. The lithological composition of the sediments and the faunal composition were used for reconstruction of past climatic changes and for the stratigraphical interpretation. Remnants of the oldest Palaeolithic culture in this region - the Acheulian type with Levalloisian technique - were found in deposits dated to the Warthanian and to the penultimate interglacial or even to the Odranian. During the Eemian, this culture coexisted with the Taubachian. For the Early Vistulian, the Levallois-Mousterian, Micoquo-Prondnikian and Charentian are characteristic cultures. Upper Palaeolithic cultures (Jerzmanowician, Aurignacian, Szeletian and then East-Gravettian) developed during younger Vistulian interstadials (Interplenivistulian) correlated with stage 3 of the oxygen isotope curve. Toward the end of the Vistulian, the Magdalenian culture and the Epigravettian appeared.
Torres, T. O. J. E. C. R. (2003). "Features of deep cave sediments: Their influence on fossil preservation." Estudios Geologicos 59(1): 195-204.
We analyse how physical and chemical deep-cave, sediment features preserve the morphological and geochemical characteristics of paleontological materials. Detrital sediment chemistry and clast size are fundamental because they provide a soft, impervious and plastic environment in which fossil remains are transported with minimal erosion. Sediment mineralogy provides a carbonate- and phosphate-buffered environment in which molecules of biological origin hydrolyze slower than in open-air environments or even at cave entrance sites. Because permafrost did not develop in the Iberian Peninsula (at least at the altitudes of inhabited caves), sediment desiccation never took place. In addition, sediment -pores were not aerated, which protected fossil remains from air (oxygen)-linked weathering. The annual -temperature variation inside sediment was negligible, which contributed to amino acid racemization dating. Collagen amino acid and amino acid racemization analysis of cave bear and man samples from cave sediments dated from different Oxygen Isotope Stages (4th: Sidrón, Annuxate, Troskaeta, El Toll, Coro Tracito, Ekain, Lezetxiki, La Pasada, Eirós; 5th: Reguerillo and Arrikrutz; 6th-7th: Sima de los Huesos) demonstrate that important amounts of almost intact collagen still remain in teeth dentine. Fossil DNA search seems to be very promising.
Bosak, P. P. P. K. J. (2003). "Magnetostratigraphy of cave sediments: Application and limits." Studia Geophysica et Geodaetica 47(2): 301-330.
The application of the magnetostratigraphy for dating of clastic and chemogenic cave sediments has been limited by the complex conditions underground and the lack of age constraints on these deposits for correlation with geomagnetic polarity timescale (GPTS). Without age constraints any correlation of obtained results cannot be explicit. Additionally, the dynamic character of cave infilling, exhumation and fossilisation expressed by unconformities within preserved sedimentary profiles can hide a substantial part of the geological time. The detailed internal division of deposits (breaks in deposition and related processes) and scarcity of fossils make the correlation of obtained magnetostratigraphic log with geomagnetic polarity timescales sometimes problematic. The analytical results confirmed that the complete step/field procedure offered by demagnetisation methods must be applied. The application of complete analysis only to pilot samples and shortened, selected field/step approach, to other samples did not offer sufficient data set for reliable interpretation.
Vit, J. (1994). "Clay minerals of the fluvial cave sediments (northern part of the Moravian karst)." Acta Universitatis Carolinae Geologica 38(2): 421-424.
Clay fraction of the clay-silty, sandy and gravelly Pleistocene sediments from the Moravian Karst were detected and estimated by semiquantitative analysis on the IR Spectrometer Perkin-Elmer 783. Varying amounts of kaolinite, illite, (+smectite), quartz, dolomite and calcite were detected. The kaolinite/illite (+smectite) ratio shows on several cave sedimentary profiles that kaolinite representation increases towards the older Pleistocene sediments. It seems to be connected with the redeposition of the older interglacial weathering crusts on the fluvial sediments. It follows from this study that clay minerals could contribute to the relative stratigraphy of the fluvial cave sediments (or to the correlations among various profiles with indistinct stratigraphic relationships) in this area. -Author Correspondence Info: Dept of Geology & Palaeontology, Masaryk Univ, Kotlarska 2, Brno, Czech Republic
Before I get into the more specific papers on my topic of clastic cave-fills, I think it's important to first cite the big dogs, and since caves are the ultimate product of unconformities, what better paper to cite than Sloss (1963). This is the paper that first described the earth's major transgressive/regressive tracts and put them into global context; many now refer to them as Sloss Sequences. The major sequence in which these paleocaverns were formed during is the Kaskaskian. If you are a geologist than this classic paper is a must-read.
The next major citation I have is a collection of articles in a book known simply as Paleokarst (1988), edited by N.P. James and P.W. Choquette. The introduction, written by the editors, makes for an excellent citation on basic karst morphology and processes. Within the book are articles by some of the modern pioneers on karst: Derek Ford and Charles Kerans. Including the intro, this collection has 19 articles which will be more than enough to cover the basics of karstification.
Since I am wanting to explore the hydrocarbon reservoir potential of these paleocaverns, I also collected references on karst reservoirs. C. Kerans' 1988 paper in the AAPG Bulletin titled Karst-Controlled Reservoir Heterogeneity is an excellent paper to start with.
A few other references I have collected are:
Evans, J. E. R. J. M. (2006). "Pennsylvanian fluvial cave sediments in the Mississippian Leadville Limestone, southwestern Colorado, U.S.A." Mountain Geologist 43(4): 283-297.
In southwestern Colorado, paleokarst of the Mississippian Leadville Limestone contains fluvial cave sediments, debrites, and fissure-fill sediments. The fluvial cave sediments form fining-upward sequences consisting of: 1) clast-supported, pebble-cobble conglomerate composed of limestone and chert clasts and siltstone intraclasts (lithofacies Gm), 2) massive sandy siltstone which may show primary current lineation (lithofacies SSm), 3) laminated siltstone-mudstone rhythmites (lithofacies Fl), and 4) massive silty mudstones (lithofacies Fm). The sequences commonly terminate with an upper mudcracked claystone drape (lithofacies Fcd). Some silty sandstone with climbing ripple lamination (lithofacies Sr) is observed. The fluvial cave sediments are interpreted as ephemeral, high-energy, flood-flow deposits (inundites) that flowed through open-framework phreatic tubes. The inundites are interbedded with debrites, speleothems, and karst-collapse breccias. The fluvial sediments are texturally and compositionally identical to the overlying Pennsylvanian Molas Formation, which has recently been reinterpreted as a loessite (eolian siltstone). The allochthonous paleocave sediments are interbedded with parautochthonous cave sediments (chaotic, mosaic, and crackle breccias) and with autochthonous cave sediments (speleothems). Observed speleothems include flowstone, dripstone, and cave pearls. Some of the inundite events were sufficiently energetic to erode and transport fragments of speleothems. Exposures of Leadville paleokarst demonstrate that: 1) phreatic tubes formed by subsurface erosion below the water-table; 2) the tubes were partially to completely filled by fluvial cave sediments; 3) individual phreatic tubes subsequently collapsed to form breakout domes (upward-widening domal structures made from karst breccias); and 4) the breakout domes were subsequently infilled by translocated loess infilling fissures and breccia matrix, speleothem formation, and multiple episodes of cementation. A vertical sequence of phreatic tubes and superimposed breakout domes suggests that regional paleogroundwater surfaces were falling during the early Pennsylvanian. This may have been controlled by the downcutting of adjacent solution valleys and/or by paleoclimate change.
Madeyska, T. C. K. (2002). "Cave fillings - A chronicle of the past. An outline of the Younger Pleistocene cave sediments study in Poland." Acta Geologica Polonica special 52(12): 75-95.
The scientific exploration of Polish cave sediments started 130 years ago. Important Palaeolithic sites were discovered and investigated from that time by archaeologists and zoologists. During the second half of the 20th century geological analysis was introduced to the cave filling study. More than 50 caves and rock shelters, differentiated according to their shape and dimensions, have been explored to date, every one of which contained subfossil animal remains. In about 30 sites, culture layers, scattered artefacts or other traces of the activity of Palaeolithic people were found. The sedimentary successions, 2-8 metres thick, consist mainly of elastic components that reflect the past climatic changes. The subfossil fauna includes animals living in tundra, steppe, forest and aquatic environments. The proportions of particular groups vary with the position in the succession. The lithological composition of the sediments and the faunal composition were used for reconstruction of past climatic changes and for the stratigraphical interpretation. Remnants of the oldest Palaeolithic culture in this region - the Acheulian type with Levalloisian technique - were found in deposits dated to the Warthanian and to the penultimate interglacial or even to the Odranian. During the Eemian, this culture coexisted with the Taubachian. For the Early Vistulian, the Levallois-Mousterian, Micoquo-Prondnikian and Charentian are characteristic cultures. Upper Palaeolithic cultures (Jerzmanowician, Aurignacian, Szeletian and then East-Gravettian) developed during younger Vistulian interstadials (Interplenivistulian) correlated with stage 3 of the oxygen isotope curve. Toward the end of the Vistulian, the Magdalenian culture and the Epigravettian appeared.
Torres, T. O. J. E. C. R. (2003). "Features of deep cave sediments: Their influence on fossil preservation." Estudios Geologicos 59(1): 195-204.
We analyse how physical and chemical deep-cave, sediment features preserve the morphological and geochemical characteristics of paleontological materials. Detrital sediment chemistry and clast size are fundamental because they provide a soft, impervious and plastic environment in which fossil remains are transported with minimal erosion. Sediment mineralogy provides a carbonate- and phosphate-buffered environment in which molecules of biological origin hydrolyze slower than in open-air environments or even at cave entrance sites. Because permafrost did not develop in the Iberian Peninsula (at least at the altitudes of inhabited caves), sediment desiccation never took place. In addition, sediment -pores were not aerated, which protected fossil remains from air (oxygen)-linked weathering. The annual -temperature variation inside sediment was negligible, which contributed to amino acid racemization dating. Collagen amino acid and amino acid racemization analysis of cave bear and man samples from cave sediments dated from different Oxygen Isotope Stages (4th: Sidrón, Annuxate, Troskaeta, El Toll, Coro Tracito, Ekain, Lezetxiki, La Pasada, Eirós; 5th: Reguerillo and Arrikrutz; 6th-7th: Sima de los Huesos) demonstrate that important amounts of almost intact collagen still remain in teeth dentine. Fossil DNA search seems to be very promising.
Bosak, P. P. P. K. J. (2003). "Magnetostratigraphy of cave sediments: Application and limits." Studia Geophysica et Geodaetica 47(2): 301-330.
The application of the magnetostratigraphy for dating of clastic and chemogenic cave sediments has been limited by the complex conditions underground and the lack of age constraints on these deposits for correlation with geomagnetic polarity timescale (GPTS). Without age constraints any correlation of obtained results cannot be explicit. Additionally, the dynamic character of cave infilling, exhumation and fossilisation expressed by unconformities within preserved sedimentary profiles can hide a substantial part of the geological time. The detailed internal division of deposits (breaks in deposition and related processes) and scarcity of fossils make the correlation of obtained magnetostratigraphic log with geomagnetic polarity timescales sometimes problematic. The analytical results confirmed that the complete step/field procedure offered by demagnetisation methods must be applied. The application of complete analysis only to pilot samples and shortened, selected field/step approach, to other samples did not offer sufficient data set for reliable interpretation.
Vit, J. (1994). "Clay minerals of the fluvial cave sediments (northern part of the Moravian karst)." Acta Universitatis Carolinae Geologica 38(2): 421-424.
Clay fraction of the clay-silty, sandy and gravelly Pleistocene sediments from the Moravian Karst were detected and estimated by semiquantitative analysis on the IR Spectrometer Perkin-Elmer 783. Varying amounts of kaolinite, illite, (+smectite), quartz, dolomite and calcite were detected. The kaolinite/illite (+smectite) ratio shows on several cave sedimentary profiles that kaolinite representation increases towards the older Pleistocene sediments. It seems to be connected with the redeposition of the older interglacial weathering crusts on the fluvial sediments. It follows from this study that clay minerals could contribute to the relative stratigraphy of the fluvial cave sediments (or to the correlations among various profiles with indistinct stratigraphic relationships) in this area. -Author Correspondence Info: Dept of Geology & Palaeontology, Masaryk Univ, Kotlarska 2, Brno, Czech Republic
Wednesday, February 3, 2010
The outcrops
I will be posting pictures of these cave-fill deposits soon. All of these outcrops are within a mile of each other near Stockton Lake, MO, and are all within the same stratigraphic unit -- Osagean Stage.
However, one of the cave-fills is much different than the others. Three are filled with sandstone whereas this other contains a black silt stone -- it actually looks a lot like a paleosol and is as black as the Heebner Shale. I have been thinking about a possible provenance for this cave-fill and so far have considered Morrowan aged silts deposited from fluvial processes, that it is actually a paleosol, or that these are the insoluable residues left over from the subaerial erosion of the Osagean limestones (a long shot that I will keep in the back of my mind). Another interesting thing about these rocks is that it is intercalated with a bright yellow clay, possibly Carnotite -- which would be a rare find in Missouri! I have collected a sample of this but am waiting to collect other samples before analysing it with our new XRD.
Determining why this cave-fill is so completly different than the others which are of the same age and close in proximity to is another question I will look to answer if a provenance for all of the rocks are found.
However, one of the cave-fills is much different than the others. Three are filled with sandstone whereas this other contains a black silt stone -- it actually looks a lot like a paleosol and is as black as the Heebner Shale. I have been thinking about a possible provenance for this cave-fill and so far have considered Morrowan aged silts deposited from fluvial processes, that it is actually a paleosol, or that these are the insoluable residues left over from the subaerial erosion of the Osagean limestones (a long shot that I will keep in the back of my mind). Another interesting thing about these rocks is that it is intercalated with a bright yellow clay, possibly Carnotite -- which would be a rare find in Missouri! I have collected a sample of this but am waiting to collect other samples before analysing it with our new XRD.
Determining why this cave-fill is so completly different than the others which are of the same age and close in proximity to is another question I will look to answer if a provenance for all of the rocks are found.
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