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Derek Ford

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Retired professor of physical environmental science, chiefly geomorphology, climate change, groundwater storage, flow and chemistry. Specialist in karst landforms and cave genesis, a pioneer of dating and paleoclimate reconstructions from speleothems. Applied work in groundwater management in soluble rocks

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Jose Ruben Guzman-Gutierrez

Universidad Humanista de las Americas

Armando Marques-Guedes

UNL - New University of Lisbon

University of Maryland

Appalachian State University

Universidade de São Paulo

Ana Rosa Gómez Cano

Institut Català de Paleontologia

Guilherme Siniciato Terra Garbino

Universidade Federal de Viçosa

Alexander Fantalkin

Tel Aviv University

Richard Cloutier

Université du Québec à Rimouski

Renata Muylaert

Massey University

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Papers by Derek Ford

The development of limestone cave systems in the dimensions of length and depth

International Journal of Speleology, Dec 1, 1978

Brazilian cave heritage under siege

Science

Influence of solar luminosity over geomagnetic and climatic cycles as derived from speleothems

International Journal of Speleology, 2004

We observed cycles presented in a luminescent solar insolation proxy record from a speleothem fro... more We observed cycles presented in a luminescent solar insolation proxy record from a speleothem from Jewel Cave, South Dakota, US. We found cycles of orbital precession with periods of 23 and 19 ka and of obliquity of 41 ka and many others from non-orbital origin in this sample. We determined the Solar origin of the cycles with durations of

Porosity and permeability enhancement in unconfined carbonate aquifers as a result of dissolution

Speleogenesis Evolution of Karst Aquifers: Huntsville, Alabama, National Speleological Society, Inc, 2000

Solution processes in carbonate aquifers that are unconfined produce networks of channels. To cha... more Solution processes in carbonate aquifers that are unconfined produce networks of channels. To characterize the enhancement of porosity and permeability by dissolution, we examine four examples that are highly contrasted in their lithologic characteristics and topographic settings:-a Paleozoic dolostone near Niagara Falls, Ontario; the Mill Hole basin in Paleozoic limestone in Mammoth Cave National Park, Kentucky; the Mesozoic chalk escarpments of southern England, and late Tertiary-Quaternary limestones of the Caribbean coast of the ...

The Many Landscapes of South Nahanni National Park

World Geomorphological Landscapes, 2016

South Nahanni National Park comprises the S. Nahanni and Ram River basins, c. 38,000 km 2 in area... more South Nahanni National Park comprises the S. Nahanni and Ram River basins, c. 38,000 km 2 in area and extending from the continental divide (Yukon boundary) eastwards to the margins of the Mackenzie River plains. Elevations range from 2500 masl (polar desert ecozone) to 200 masl (boreal forest). Continuous permafrost conditions begin c. 600 masl. The geomorphic landscapes are exceptionally rich and diverse, including (1) rugged Cordilleran glacial landforms (cirques, arêtes, horn peaks, etc.) in resistant batholithic rocks of Cretaceous age in the west; (2) broader glacial troughs and V-form fluvial tributaries in weak, structurally deformed Lower Paleozoic sedimentary strata in the centre; (3) deep antecedent river canyons, stripped anticlines and synclines in stronger Upper Paleozoic limestones and dolostones in the east, with (4) an inter-basin belt of karst landforms and caves, the most accentuated reported in any sub-arctic or arctic region; (5) thick deposits of sand, silt and clay in proglacial lakes created by Laurentide continental ice blocking the river outlets to the Mackenzie plains: the deposits are terraced or dissected and, in the last 25 years, beginning to display widespread slumping that is due to the thawing of ground ice.

Derek Ford oral history interview with Dr. Philip Van Beynen, January 24, 2008

This oral history may be used for research, instruction, and private study under the provisions o... more This oral history may be used for research, instruction, and private study under the provisions of the Fair Use. Fair Use is a provision of the United States Copyright Law (United States Code, Title 17, section 107), which allows limited use of copyrighted materials under certain conditions. Fair Use limits the amount of material that may be used.

Cronología de la Terminación II y del Último Periodo Interglacial en el norte de España a partir de los registros de isótopos estables de estalagmitas procedentes de la Cueva del Cobre (Palencia)

New insight into the timing and structure of the Last Interglacial Period (Eemian) was obtained t... more New insight into the timing and structure of the Last Interglacial Period (Eemian) was obtained through U-Th dating of four speleothems from Northern Spain and an analysis of their stable isotope records. The four stalagmites examined were collected from different levels of Cueva del Cobre, a cold high-mountain cave in the Cantabrian Ranges (N Spain), in which speleothem growth took place essentially during the warmer interestadials. Through 18 TIMS and ICPMS datings and 263 stable isotope analyses, the onset of the Eemian interglacial period was precisely dated at 150±2 ka, an age consistent with a few other palaeoclimatic records but notably younger than the age ascribed by the Milankovitch theory. We also date the Eemian-Weichselian transition (~115 ka) for the fi rst time in the Iberian Peninsula. U-Th ages revealed a consistent anomaly at ~105-100 ka BP, which could be related to a drastic environmental change during the MIS-5c interestadial. This event would have caused the resetting of the U-Th system at the base of the stalagmites during a short time interval. In addition, we propose a new simple geochemical test to ensure the lack of disturbance of this type of samples for dating purposes.

Correlated strontium, carbon and oxygen isotopes in carbonate gangue at the Nanisivik zinc-lead deposits, northern Baffin Island, N.W.T. Canada

Chemical Geology: Isotope Geoscience section, 1991

... Correlated strontium, carbon and oxygen isotopes in carbonate gangue at the Nanisivik zinclea... more

Discovery of a submerged relic reef and shoreline off Grand Cayman: further support for an early Holocene jump in sea level

Sedimentary Geology, 2002

Drilling close to the base of a submerged sea-cliff on the terraced eastern shelf of Grand Cayman... more Drilling close to the base of a submerged sea-cliff on the terraced eastern shelf of Grand Cayman has revealed a relic Acropora palmata reef at a depth of 21 m below msl. Ten cores from its crest are principally composed of cobble-sized clasts of A. palmata set in a matrix of cemented skeletal grainstone. The clasts have a distinctive succession of encrusters that indicate rapid burial: a photophilic association of crustose coralline algae, foraminifera and vermetid gastropods superimposed by a cryptic association of sclerosponges, foraminifera and serpulids. In addition to rapid burial, U-Th thermal ionization mass spectrometer (TIMS) dating of coral clasts within 1m of the relic-reef surface indicates minor temporal mixing with ages between 8.9 and 8.1 ka. Such mixing and rapid burial is consistent with a hurricane deposit and is identical to deposits found on the crests of modern reefs. In relation to its age, the preservation of a À 18.5-m intertidal notch cut into the submerged sea-cliff on the western shelf of Grand Cayman implies that the crest of the relic reef has been lowered 1.5-2 m by marine abrasion/ bioerosion at a rate of f 0.25 mm yr À 1. Reconstructing this eroded section using average Holocene accretion rates indicates that the reef likely ceased accreting at f 7.6 ka at a depth of f 19 m. Comparing these data with other relic reefs in the Caribbean indicates that the relic reef on Grand Cayman died within 160 years of relic reefs on Barbados, St. Croix, St. Thomas and north Florida. This narrow interval of reef demise also coincides with the time when modern reefs were establishing themselves some 4-9 m higher upslope-a fact that can only be resolved by invoking a rapid 6-m jump in sea level f 7.5 ka ago. Such a jump would also account for two unexplained events around this time: the restricted interval of global delta initiation and the catastrophic flooding of the glacially lowered Black Sea.

Karst Development in the Glaciated and Permafrostregions of the Northwest Territories, Canada

The Northwest Territories of Canada are ~1.2 million km2 in area and appear to contain a greater ... more The Northwest Territories of Canada are ~1.2 million km2 in area and appear to contain a greater extent and diversity of karst landforms than has been described in any other region of the Arctic or sub-Arctic. The Mackenzie River drains most of the area. West of the River, the Mackenzie Mountains contain spectacular highland karsts such as Nahanni (Lat. 62° N) and Canol Road (Lat. 65° N) that the author has described at previous International Speleological Congresses. This paper summarizes samples of the mountain and lowland karst between Lats. 64–67° N that are located east of the River. The Franklin Mountains there are east-facing cuestas created by over-thrusting from the west. Maximum elevations are ~1,000 m a.s.l., diminishing eastwards where the cuestas are replaced by undeformed plateaus of dolomite at 300–400 m asl that overlook Great Bear Lake. In contrast to the Mackenzie Mountains (which are generally higher) all of this terrain was covered repeatedly by Laurentide Contin...

Carbonate-Hosted Massive Sulfide Deposits and Hypogene Speleogenesis: A Case Study from Nanisivik Zinc/Lead Mine Baffin Island, Canada

Hypogene Karst Regions and Caves of the World

Nanisivik zinc/lead mine is located at Lat. 73°N in northwestern Baffin Island. The host rock is ... more Nanisivik zinc/lead mine is located at Lat. 73°N in northwestern Baffin Island. The host rock is a pervasively dolomitized Proterozoic platform carbonate overlain by a shale aquitard. The principal deposit, the Main Ore, is of zinc, lead, and iron sulfide plus gangue minerals, chiefly secondary dolomite. It extends for 3 km along a horst and is terminated at both ends by modern valley entrenchments. The Main Ore body is consistently *100 m wide and five to seven m thick. The ceiling is a wide, horizontal corrosion bevel. Within the Main Ore are two or more generations of tapered fins of dolomite that extend into the cavity. The fin edges are sinuous, some meandering. Sharp, horizontal corrosion notches 20-30 cm high extend into the dolomite walls. They are filled with layered pyrites which continue into the ore body, truncating earlier, dipping mineral bodies. Sedimentary textures suggest that the ore cavity formed by paragenesis in a channel-flow mode, with ore and gangue deposition on the floor taking place in tandem with dissolutional cavity creation upward. Fluid inclusions indicate derivation of the metals from exchange reactions with metalliferous sediments (the underlying shales), indicating low water/rock ratios and moderate temperatures. The ore fluids were similar to oilfield brines. Sulfur isotope fractionations indicate temperatures of 90-150 ± 40°C, suggesting that the Main Ore formed along a gas/brine interface at a depth of at least 1600 m. Latest studies suggest a Grenville age (*1.1 Ga) for the Main Ore.

Ranges (amplitudes) of isotopic ratios in speleothems, with particular reference to samples from the centre of North America

Acta Geologica Polonica, 2003

This paper compares unstable and stable isotope ratios measured in a speleothem core from the Nev... more This paper compares unstable and stable isotope ratios measured in a speleothem core from the Nevada desert (the well-known DH 11) with speleothems at the centre of the continent in the Black Hills of South Dakota. All samples grew over most of the past 500,000 y. The thermal calcite in the large Nevadan desert basin displays a range of the initial U ratio ( 234 U/ 238 U0) of only 0.25 and is much enriched in 234 U, reflecting selective leaching in a very low energy weathering environment. Similar thermal calcite from a much smaller basin the Black Hills (Wind Cave) is less homogenised (U/U0 range is ~0.5) and less enriched as a consequence of its more vigorous sem-arid weathering environment. Both display glacial-interglacial cyclicity in the ratio. A vadose speleothem from Jewel Cave, Black Hills, has a U/U 0 range of 0.75 and many erratic features attributable to rapidly changing local conditions in the overlying tall grass- coniferous forest vegetal transition. O and C stable is...

Ice Caves in Canada

Ice Caves

Professor Jean NICOD

Physio-Géo

Raised Marine Terraces Along the Gulf of Aden Coast of Somalia

Physical Geography

ABSTRACT Mapping in the Galweda-Elayu area of northern Somalia has revealed depositional and eros... more ABSTRACT Mapping in the Galweda-Elayu area of northern Somalia has revealed depositional and erosional marine terraces at elevations of approximately 16 m, 8 m, and 2 m. These terraces vary from 0–2300 m, 200–2200 m, and 0–800 m in width, respectively. Sediments exposed in stream-valley walls demonstrate that the two higher terraces were formed by marine transgressions followed later by regressions to below present sea level. Beach ridges on the terraced alluvial fan at the mouth of togga Galweda imply that sea level and/or land elevation varied by at least 6 m during the formation of the 16-m terrace and by at least 3 m during the formation of the 8-m terrace. 230Th/234U ages of corals suggest that the 8-m terrace was formed during deep-sea isotope substage 5c (105 kyr B.P.) and the 2-m terrace during substage 5a (80 kyr B.P.). A 7-kyr-old coral from above the present storm beach on the outer flanks of the 2-m terrace suggests that sea level in the Gulf of Aden was close to its present level by the middle Holocene. No material suitable for dating was recovered from the 16-m terrace, but on morphological grounds and based on marine-terrace elevations elsewhere in the Red Sea-Gulf of Aden rift zone, we believe that the 16-m terrace was formed during isotope substage 5e (132–120 kyr B.P.), when global sea level was about 6 m above present.

Underwater Dissolutional Pitting on Dolostones, Lake Huron-Georgian Bay, Ontario

Physical Geography

ABSTRACT This paper examines underwater dissolutional pitting along the dolomitic shorelines of t... more ABSTRACT This paper examines underwater dissolutional pitting along the dolomitic shorelines of the Bruce Peninsula around Tobermory, Ontario. Research was conducted from the modern spray and swash zone to depths of 25 m at four sites: Little Cove, Big Tub, Marr Lake, and Cove Island. The morphology of sample pits was measured, rock samples were collected, and comprehensive water analyses were completed. The most striking result to emerge from this work was a strong positive relationship (r2 = .93) between pit depth and water depth. Variations in the physical lithology obscured all other relationships between the morphological parameters that were studied. The detailed variations of lithology between sites and between water depths at a given site are difficult to quantify and were not attempted in this project. The Tobermory sites are distinct because they have been both totally emerged and totally submerged during the last 12,000 years. A model to explain pit genesis including initiation and enlargement incorporating this post glacial lake level history is proposed. [Key words: karren, pitting, littoral, dolostone.]

Les "Forêts de Pierre" ou "Stone forests" de Lunan (Yunnan, Chine)

Karstologia : revue de karstologie et de spéléologie physique

Concluding Discussion

Arctic and Alpine Research

Stable isotope studies of cave seepage water

Chemical Geology

ABSTRACT

Clastic Sediments in Castleguard Cave, Columbia Icefields, Alberta, Canada

Arctic and Alpine Research

Castleguard Cave contains a variety of clastic sediments of both allochthonous and autochthonous ... more Castleguard Cave contains a variety of clastic sediments of both allochthonous and autochthonous origin. The head of the cave, lying beneath the Columbia lcefield, displays breakdown and glaciofluvial injecta that are ancient. Principal deposits in the central cave are the eroded remains of at least three phases of silt filling. These are interpreted as varved sequences deposited under full glacial conditions. They are older than 140,000 BP. A channel abandonment facies occupies the inner part of the downstream entrance complex. The outer part is prone to flooding today and contains a remarkable shingle beach formed in situ where floodwaters must rise vertically. CLASTIC DEPOSITS IN CAVES Caves may function as giant sediment traps, preserving evidences of past erosional, floral, etc., phases of a region long after these have been destroyed at the surface. Cave sedimentary deposits include organic materials, chemical precipitates, and clastic sediments; often, there are complex sequences containing all three kinds. It is convenient to differentiate between entrance deposits and those of cave interiors; the former tend to be more complex because of dripline and colluvial effects, colonization by external flora and fauna, etc. They have been the subject of much detailed investigation and classification because of their archaeological importance (e.g., Laville, 1975). Distinctive entrance facies are absent at Castleguard Cave because the annual floods sweep the entry clean.

The development of limestone cave systems in the dimensions of length and depth

International Journal of Speleology, Dec 1, 1978

Brazilian cave heritage under siege

Science

Influence of solar luminosity over geomagnetic and climatic cycles as derived from speleothems

International Journal of Speleology, 2004

We observed cycles presented in a luminescent solar insolation proxy record from a speleothem fro... more We observed cycles presented in a luminescent solar insolation proxy record from a speleothem from Jewel Cave, South Dakota, US. We found cycles of orbital precession with periods of 23 and 19 ka and of obliquity of 41 ka and many others from non-orbital origin in this sample. We determined the Solar origin of the cycles with durations of

Porosity and permeability enhancement in unconfined carbonate aquifers as a result of dissolution

Speleogenesis Evolution of Karst Aquifers: Huntsville, Alabama, National Speleological Society, Inc, 2000

Solution processes in carbonate aquifers that are unconfined produce networks of channels. To cha... more Solution processes in carbonate aquifers that are unconfined produce networks of channels. To characterize the enhancement of porosity and permeability by dissolution, we examine four examples that are highly contrasted in their lithologic characteristics and topographic settings:-a Paleozoic dolostone near Niagara Falls, Ontario; the Mill Hole basin in Paleozoic limestone in Mammoth Cave National Park, Kentucky; the Mesozoic chalk escarpments of southern England, and late Tertiary-Quaternary limestones of the Caribbean coast of the ...

The Many Landscapes of South Nahanni National Park

World Geomorphological Landscapes, 2016

South Nahanni National Park comprises the S. Nahanni and Ram River basins, c. 38,000 km 2 in area... more South Nahanni National Park comprises the S. Nahanni and Ram River basins, c. 38,000 km 2 in area and extending from the continental divide (Yukon boundary) eastwards to the margins of the Mackenzie River plains. Elevations range from 2500 masl (polar desert ecozone) to 200 masl (boreal forest). Continuous permafrost conditions begin c. 600 masl. The geomorphic landscapes are exceptionally rich and diverse, including (1) rugged Cordilleran glacial landforms (cirques, arêtes, horn peaks, etc.) in resistant batholithic rocks of Cretaceous age in the west; (2) broader glacial troughs and V-form fluvial tributaries in weak, structurally deformed Lower Paleozoic sedimentary strata in the centre; (3) deep antecedent river canyons, stripped anticlines and synclines in stronger Upper Paleozoic limestones and dolostones in the east, with (4) an inter-basin belt of karst landforms and caves, the most accentuated reported in any sub-arctic or arctic region; (5) thick deposits of sand, silt and clay in proglacial lakes created by Laurentide continental ice blocking the river outlets to the Mackenzie plains: the deposits are terraced or dissected and, in the last 25 years, beginning to display widespread slumping that is due to the thawing of ground ice.

Derek Ford oral history interview with Dr. Philip Van Beynen, January 24, 2008

This oral history may be used for research, instruction, and private study under the provisions o... more This oral history may be used for research, instruction, and private study under the provisions of the Fair Use. Fair Use is a provision of the United States Copyright Law (United States Code, Title 17, section 107), which allows limited use of copyrighted materials under certain conditions. Fair Use limits the amount of material that may be used.

Cronología de la Terminación II y del Último Periodo Interglacial en el norte de España a partir de los registros de isótopos estables de estalagmitas procedentes de la Cueva del Cobre (Palencia)

New insight into the timing and structure of the Last Interglacial Period (Eemian) was obtained t... more New insight into the timing and structure of the Last Interglacial Period (Eemian) was obtained through U-Th dating of four speleothems from Northern Spain and an analysis of their stable isotope records. The four stalagmites examined were collected from different levels of Cueva del Cobre, a cold high-mountain cave in the Cantabrian Ranges (N Spain), in which speleothem growth took place essentially during the warmer interestadials. Through 18 TIMS and ICPMS datings and 263 stable isotope analyses, the onset of the Eemian interglacial period was precisely dated at 150±2 ka, an age consistent with a few other palaeoclimatic records but notably younger than the age ascribed by the Milankovitch theory. We also date the Eemian-Weichselian transition (~115 ka) for the fi rst time in the Iberian Peninsula. U-Th ages revealed a consistent anomaly at ~105-100 ka BP, which could be related to a drastic environmental change during the MIS-5c interestadial. This event would have caused the resetting of the U-Th system at the base of the stalagmites during a short time interval. In addition, we propose a new simple geochemical test to ensure the lack of disturbance of this type of samples for dating purposes.

Correlated strontium, carbon and oxygen isotopes in carbonate gangue at the Nanisivik zinc-lead deposits, northern Baffin Island, N.W.T. Canada

Chemical Geology: Isotope Geoscience section, 1991

... Correlated strontium, carbon and oxygen isotopes in carbonate gangue at the Nanisivik zinclea... more

Discovery of a submerged relic reef and shoreline off Grand Cayman: further support for an early Holocene jump in sea level

Sedimentary Geology, 2002

Drilling close to the base of a submerged sea-cliff on the terraced eastern shelf of Grand Cayman... more Drilling close to the base of a submerged sea-cliff on the terraced eastern shelf of Grand Cayman has revealed a relic Acropora palmata reef at a depth of 21 m below msl. Ten cores from its crest are principally composed of cobble-sized clasts of A. palmata set in a matrix of cemented skeletal grainstone. The clasts have a distinctive succession of encrusters that indicate rapid burial: a photophilic association of crustose coralline algae, foraminifera and vermetid gastropods superimposed by a cryptic association of sclerosponges, foraminifera and serpulids. In addition to rapid burial, U-Th thermal ionization mass spectrometer (TIMS) dating of coral clasts within 1m of the relic-reef surface indicates minor temporal mixing with ages between 8.9 and 8.1 ka. Such mixing and rapid burial is consistent with a hurricane deposit and is identical to deposits found on the crests of modern reefs. In relation to its age, the preservation of a À 18.5-m intertidal notch cut into the submerged sea-cliff on the western shelf of Grand Cayman implies that the crest of the relic reef has been lowered 1.5-2 m by marine abrasion/ bioerosion at a rate of f 0.25 mm yr À 1. Reconstructing this eroded section using average Holocene accretion rates indicates that the reef likely ceased accreting at f 7.6 ka at a depth of f 19 m. Comparing these data with other relic reefs in the Caribbean indicates that the relic reef on Grand Cayman died within 160 years of relic reefs on Barbados, St. Croix, St. Thomas and north Florida. This narrow interval of reef demise also coincides with the time when modern reefs were establishing themselves some 4-9 m higher upslope-a fact that can only be resolved by invoking a rapid 6-m jump in sea level f 7.5 ka ago. Such a jump would also account for two unexplained events around this time: the restricted interval of global delta initiation and the catastrophic flooding of the glacially lowered Black Sea.

Karst Development in the Glaciated and Permafrostregions of the Northwest Territories, Canada

The Northwest Territories of Canada are ~1.2 million km2 in area and appear to contain a greater ... more The Northwest Territories of Canada are ~1.2 million km2 in area and appear to contain a greater extent and diversity of karst landforms than has been described in any other region of the Arctic or sub-Arctic. The Mackenzie River drains most of the area. West of the River, the Mackenzie Mountains contain spectacular highland karsts such as Nahanni (Lat. 62° N) and Canol Road (Lat. 65° N) that the author has described at previous International Speleological Congresses. This paper summarizes samples of the mountain and lowland karst between Lats. 64–67° N that are located east of the River. The Franklin Mountains there are east-facing cuestas created by over-thrusting from the west. Maximum elevations are ~1,000 m a.s.l., diminishing eastwards where the cuestas are replaced by undeformed plateaus of dolomite at 300–400 m asl that overlook Great Bear Lake. In contrast to the Mackenzie Mountains (which are generally higher) all of this terrain was covered repeatedly by Laurentide Contin...

Carbonate-Hosted Massive Sulfide Deposits and Hypogene Speleogenesis: A Case Study from Nanisivik Zinc/Lead Mine Baffin Island, Canada

Hypogene Karst Regions and Caves of the World

Nanisivik zinc/lead mine is located at Lat. 73°N in northwestern Baffin Island. The host rock is ... more Nanisivik zinc/lead mine is located at Lat. 73°N in northwestern Baffin Island. The host rock is a pervasively dolomitized Proterozoic platform carbonate overlain by a shale aquitard. The principal deposit, the Main Ore, is of zinc, lead, and iron sulfide plus gangue minerals, chiefly secondary dolomite. It extends for 3 km along a horst and is terminated at both ends by modern valley entrenchments. The Main Ore body is consistently *100 m wide and five to seven m thick. The ceiling is a wide, horizontal corrosion bevel. Within the Main Ore are two or more generations of tapered fins of dolomite that extend into the cavity. The fin edges are sinuous, some meandering. Sharp, horizontal corrosion notches 20-30 cm high extend into the dolomite walls. They are filled with layered pyrites which continue into the ore body, truncating earlier, dipping mineral bodies. Sedimentary textures suggest that the ore cavity formed by paragenesis in a channel-flow mode, with ore and gangue deposition on the floor taking place in tandem with dissolutional cavity creation upward. Fluid inclusions indicate derivation of the metals from exchange reactions with metalliferous sediments (the underlying shales), indicating low water/rock ratios and moderate temperatures. The ore fluids were similar to oilfield brines. Sulfur isotope fractionations indicate temperatures of 90-150 ± 40°C, suggesting that the Main Ore formed along a gas/brine interface at a depth of at least 1600 m. Latest studies suggest a Grenville age (*1.1 Ga) for the Main Ore.

Ranges (amplitudes) of isotopic ratios in speleothems, with particular reference to samples from the centre of North America

Acta Geologica Polonica, 2003

This paper compares unstable and stable isotope ratios measured in a speleothem core from the Nev... more This paper compares unstable and stable isotope ratios measured in a speleothem core from the Nevada desert (the well-known DH 11) with speleothems at the centre of the continent in the Black Hills of South Dakota. All samples grew over most of the past 500,000 y. The thermal calcite in the large Nevadan desert basin displays a range of the initial U ratio ( 234 U/ 238 U0) of only 0.25 and is much enriched in 234 U, reflecting selective leaching in a very low energy weathering environment. Similar thermal calcite from a much smaller basin the Black Hills (Wind Cave) is less homogenised (U/U0 range is ~0.5) and less enriched as a consequence of its more vigorous sem-arid weathering environment. Both display glacial-interglacial cyclicity in the ratio. A vadose speleothem from Jewel Cave, Black Hills, has a U/U 0 range of 0.75 and many erratic features attributable to rapidly changing local conditions in the overlying tall grass- coniferous forest vegetal transition. O and C stable is...

Ice Caves in Canada

Ice Caves

Professor Jean NICOD

Physio-Géo

Raised Marine Terraces Along the Gulf of Aden Coast of Somalia

Physical Geography

ABSTRACT Mapping in the Galweda-Elayu area of northern Somalia has revealed depositional and eros... more ABSTRACT Mapping in the Galweda-Elayu area of northern Somalia has revealed depositional and erosional marine terraces at elevations of approximately 16 m, 8 m, and 2 m. These terraces vary from 0–2300 m, 200–2200 m, and 0–800 m in width, respectively. Sediments exposed in stream-valley walls demonstrate that the two higher terraces were formed by marine transgressions followed later by regressions to below present sea level. Beach ridges on the terraced alluvial fan at the mouth of togga Galweda imply that sea level and/or land elevation varied by at least 6 m during the formation of the 16-m terrace and by at least 3 m during the formation of the 8-m terrace. 230Th/234U ages of corals suggest that the 8-m terrace was formed during deep-sea isotope substage 5c (105 kyr B.P.) and the 2-m terrace during substage 5a (80 kyr B.P.). A 7-kyr-old coral from above the present storm beach on the outer flanks of the 2-m terrace suggests that sea level in the Gulf of Aden was close to its present level by the middle Holocene. No material suitable for dating was recovered from the 16-m terrace, but on morphological grounds and based on marine-terrace elevations elsewhere in the Red Sea-Gulf of Aden rift zone, we believe that the 16-m terrace was formed during isotope substage 5e (132–120 kyr B.P.), when global sea level was about 6 m above present.

Underwater Dissolutional Pitting on Dolostones, Lake Huron-Georgian Bay, Ontario

Physical Geography

ABSTRACT This paper examines underwater dissolutional pitting along the dolomitic shorelines of t... more ABSTRACT This paper examines underwater dissolutional pitting along the dolomitic shorelines of the Bruce Peninsula around Tobermory, Ontario. Research was conducted from the modern spray and swash zone to depths of 25 m at four sites: Little Cove, Big Tub, Marr Lake, and Cove Island. The morphology of sample pits was measured, rock samples were collected, and comprehensive water analyses were completed. The most striking result to emerge from this work was a strong positive relationship (r2 = .93) between pit depth and water depth. Variations in the physical lithology obscured all other relationships between the morphological parameters that were studied. The detailed variations of lithology between sites and between water depths at a given site are difficult to quantify and were not attempted in this project. The Tobermory sites are distinct because they have been both totally emerged and totally submerged during the last 12,000 years. A model to explain pit genesis including initiation and enlargement incorporating this post glacial lake level history is proposed. [Key words: karren, pitting, littoral, dolostone.]

Les "Forêts de Pierre" ou "Stone forests" de Lunan (Yunnan, Chine)

Karstologia : revue de karstologie et de spéléologie physique

Concluding Discussion

Arctic and Alpine Research

Stable isotope studies of cave seepage water

Chemical Geology

ABSTRACT

Clastic Sediments in Castleguard Cave, Columbia Icefields, Alberta, Canada

Arctic and Alpine Research

Castleguard Cave contains a variety of clastic sediments of both allochthonous and autochthonous ... more Castleguard Cave contains a variety of clastic sediments of both allochthonous and autochthonous origin. The head of the cave, lying beneath the Columbia lcefield, displays breakdown and glaciofluvial injecta that are ancient. Principal deposits in the central cave are the eroded remains of at least three phases of silt filling. These are interpreted as varved sequences deposited under full glacial conditions. They are older than 140,000 BP. A channel abandonment facies occupies the inner part of the downstream entrance complex. The outer part is prone to flooding today and contains a remarkable shingle beach formed in situ where floodwaters must rise vertically. CLASTIC DEPOSITS IN CAVES Caves may function as giant sediment traps, preserving evidences of past erosional, floral, etc., phases of a region long after these have been destroyed at the surface. Cave sedimentary deposits include organic materials, chemical precipitates, and clastic sediments; often, there are complex sequences containing all three kinds. It is convenient to differentiate between entrance deposits and those of cave interiors; the former tend to be more complex because of dripline and colluvial effects, colonization by external flora and fauna, etc. They have been the subject of much detailed investigation and classification because of their archaeological importance (e.g., Laville, 1975). Distinctive entrance facies are absent at Castleguard Cave because the annual floods sweep the entry clean.