Glacio-lacustrine sedimentation in newly discovered paleo-lakes, Westland, New Zealand

<p>The remnant effects of Quaternary glaciation dominate the geomorphology of South Westland, New Zealand. Well-constrained glaciogenic records for the Last Glacial Maximum (LGM) (~MIS 2) show ice to have extended significant distances across the Westland piedmont, becoming tidewater calving in places. Despite clear evidence for glacial advance, landscape response to glacial retreat remains relatively poorly understood, with few described sedimentary sequences clearly recording deglaciation processes. A 240-metre thick glacio-lacustrine sedimentary sequence intercepted by drilling in the Whataroa Valley (DFDP-2) provides the first compelling evidence of pro-glacial lake formation in response to glacial retreat in Westland. To understand the vertical facies succession observed in this sequence, two glacio-lacustrine facies schemes and depositional models were developed. To do this, previously unmapped glacio-lacustrine sedimentary sequences in the Westland region underwent detailed sedimentological analysis to identify key glacio-lacustrine facies. In the Waitangitaona and Arahura river valleys, the presence of glacio-lacustrine sequences is also used to mark paleo-lake formation in the respective catchments. Using the facies scheme and depositional models, together with 14C chronology and sedimentological analysis, a series of conclusions are developed from the DFDP-2 sequence: 1) Deposition occurred in an over-deepened glacial trough, with the sequence consisting of a basal diamictite, overlain by a ~ 140-metre interval of lacustrine siltstones and sandstones. 2) The lower ~ 180-metres of sediment accumulated in 659 ± 151 yrs between 16609 ± 151 and 15994 ± 94 cal. yr BP, as the depositional environment at the drill-site evolved from an ice contact to an ice distal lacustrine setting. 3) Extremely rapid sedimentation rates, as well as high lake levels allowed the preservation of glacially over-steepened bedrock slopes beneath the Whataroa Valley. The formation of a previously unknown, ~190 km2 pro-glacial lake on the Whataroa piedmont is inferred from the DFDP-2 sequence, with lake formation causing accelerated glacial retreat from the late LGM maxima. The presence of several catchments with comparable piedmont geometry suggests pro-glacial lake formation may have been a common response to glacial retreat in Westland. For a period, pro-glacial lakes may have been a significant transitory feature on the Westland landscape.</p>

Glacio-lacustrine sedimentation in newly discovered paleo-lakes, Westland, New Zealand

<p>The remnant effects of Quaternary glaciation dominate the geomorphology of South Westland, New Zealand. Well-constrained glaciogenic records for the Last Glacial Maximum (LGM) (~MIS 2) show ice to have extended significant distances across the Westland piedmont, becoming tidewater calving in places. Despite clear evidence for glacial advance, landscape response to glacial retreat remains relatively poorly understood, with few described sedimentary sequences clearly recording deglaciation processes. A 240-metre thick glacio-lacustrine sedimentary sequence intercepted by drilling in the Whataroa Valley (DFDP-2) provides the first compelling evidence of pro-glacial lake formation in response to glacial retreat in Westland. To understand the vertical facies succession observed in this sequence, two glacio-lacustrine facies schemes and depositional models were developed. To do this, previously unmapped glacio-lacustrine sedimentary sequences in the Westland region underwent detailed sedimentological analysis to identify key glacio-lacustrine facies. In the Waitangitaona and Arahura river valleys, the presence of glacio-lacustrine sequences is also used to mark paleo-lake formation in the respective catchments. Using the facies scheme and depositional models, together with 14C chronology and sedimentological analysis, a series of conclusions are developed from the DFDP-2 sequence: 1) Deposition occurred in an over-deepened glacial trough, with the sequence consisting of a basal diamictite, overlain by a ~ 140-metre interval of lacustrine siltstones and sandstones. 2) The lower ~ 180-metres of sediment accumulated in 659 ± 151 yrs between 16609 ± 151 and 15994 ± 94 cal. yr BP, as the depositional environment at the drill-site evolved from an ice contact to an ice distal lacustrine setting. 3) Extremely rapid sedimentation rates, as well as high lake levels allowed the preservation of glacially over-steepened bedrock slopes beneath the Whataroa Valley. The formation of a previously unknown, ~190 km2 pro-glacial lake on the Whataroa piedmont is inferred from the DFDP-2 sequence, with lake formation causing accelerated glacial retreat from the late LGM maxima. The presence of several catchments with comparable piedmont geometry suggests pro-glacial lake formation may have been a common response to glacial retreat in Westland. For a period, pro-glacial lakes may have been a significant transitory feature on the Westland landscape.</p>

Reconstructing Neogene Climate and Glacial History of Southern McMurdo Sound, Antarctica

<p>Understanding the glacial changes that have occurred in southern McMurdo Sound throughout the Neogene makes an important contribution to reconstructing Antarctic ice volume changes during past periods of climatic warmth, and provides insight into future possible response of the ice sheet. Fossiliferous glacimarine deposits previously identified throughout McMurdo Sound have provided inferences on past changes in ice volume and the implications for global sea level. This study investigates new stratigraphic sections comprising fossiliferous glacimarine sediments from two locations on the flanks of Mount Discovery and one on Brown Peninsula at ~150m above present day sea-level. The aim of this thesis is to undertake a sedimentological, facies and glacimarine sequence stratigraphic analysis together with a quantitative assessment of the constituent micro and macrofossils in order to determine depositional processes, changes in environment and implications for glacial variability in the southern McMurdo Sound. Up to four distinct sedimentary cycles are evident in the Mt Discovery sections with each cycle consisting of: 1. A basal glacial surface of erosion (GSE) or its correlative conformity (CC) seaward of the grounding line, displaying an abrupt transition from a more distal facies to a more proximal facies. 2. A sharp-based massive diamictite displaying physical intermixing of subjacent lithologies, intra formational clasts, soft sediment deformation features, clast rotation features, and a lack of bioturbation, interpreted as subglacial, or in very close proximity to a marine grounding line. In some cases stratified diamictites overly correlative conformities displaying clast alignment, graded beds, and weak decimeter scale parallel bedding in the matrix, interpreted as grounding-line proximal sediment gravity flows or rain-out from ice melt. 3. In some cases, the diamictite passes gradationally-upwards or is sharply overlain by a conglomerate representing appearance of glacimarine fluvio-deltaic deposition or debris flows as the glacier grounding line begins to retreat. 4. Conglomerates are overlain, often sharply, by hemipelagic laminated or massive mudstone and represent the most ice distal and marine part of the sequence at the interglacial minima. 5. A proglacial facies succession is sometimes preserved below the GSE or correlative conformity marking the top of the sequence and usually consists of a transition from mudstone facies into grounding zone proximal conglomerates during re-advance of the grounding line. Lithofacies analysis supported by sediment grainsize, the results of a foraminiferal census and macrofaunal identifications conducted on each facies imply deposition on the continental shelf in depths of up to 400 m, during oscillations in the proximity of a marine grounding line. Radiocarbon dating of constituent macrofauna (barnacle plates) reported only background ¹⁴C implying an age of deposition older than the Last Glacial Maximum. The present day elevation of the site and a model developed here using glacio-iostatic loading and unloading implies that the Mt Discovery sites have been above sea-level for approximately the last ~2.7Ma. Given their inferred association with Scallop Hill Formation and faunal similarity to sequences in the nearby ANDRILL drill cores, a Pliocene age is considered most likely. This finding is consistent with previous investigations that indicate a dynamic, sub-polar marine-terminating ice sheet margin in Southern McMurdo Sound during the Pliocene, with periods of open ice shelf free conditions potentially associated with more frequent regional collapse and retreat events of a marine-based ice sheet in the Ross Sea embayment.</p>

Reconstructing Neogene Climate and Glacial History of Southern McMurdo Sound, Antarctica

<p>Understanding the glacial changes that have occurred in southern McMurdo Sound throughout the Neogene makes an important contribution to reconstructing Antarctic ice volume changes during past periods of climatic warmth, and provides insight into future possible response of the ice sheet. Fossiliferous glacimarine deposits previously identified throughout McMurdo Sound have provided inferences on past changes in ice volume and the implications for global sea level. This study investigates new stratigraphic sections comprising fossiliferous glacimarine sediments from two locations on the flanks of Mount Discovery and one on Brown Peninsula at ~150m above present day sea-level. The aim of this thesis is to undertake a sedimentological, facies and glacimarine sequence stratigraphic analysis together with a quantitative assessment of the constituent micro and macrofossils in order to determine depositional processes, changes in environment and implications for glacial variability in the southern McMurdo Sound. Up to four distinct sedimentary cycles are evident in the Mt Discovery sections with each cycle consisting of: 1. A basal glacial surface of erosion (GSE) or its correlative conformity (CC) seaward of the grounding line, displaying an abrupt transition from a more distal facies to a more proximal facies. 2. A sharp-based massive diamictite displaying physical intermixing of subjacent lithologies, intra formational clasts, soft sediment deformation features, clast rotation features, and a lack of bioturbation, interpreted as subglacial, or in very close proximity to a marine grounding line. In some cases stratified diamictites overly correlative conformities displaying clast alignment, graded beds, and weak decimeter scale parallel bedding in the matrix, interpreted as grounding-line proximal sediment gravity flows or rain-out from ice melt. 3. In some cases, the diamictite passes gradationally-upwards or is sharply overlain by a conglomerate representing appearance of glacimarine fluvio-deltaic deposition or debris flows as the glacier grounding line begins to retreat. 4. Conglomerates are overlain, often sharply, by hemipelagic laminated or massive mudstone and represent the most ice distal and marine part of the sequence at the interglacial minima. 5. A proglacial facies succession is sometimes preserved below the GSE or correlative conformity marking the top of the sequence and usually consists of a transition from mudstone facies into grounding zone proximal conglomerates during re-advance of the grounding line. Lithofacies analysis supported by sediment grainsize, the results of a foraminiferal census and macrofaunal identifications conducted on each facies imply deposition on the continental shelf in depths of up to 400 m, during oscillations in the proximity of a marine grounding line. Radiocarbon dating of constituent macrofauna (barnacle plates) reported only background ¹⁴C implying an age of deposition older than the Last Glacial Maximum. The present day elevation of the site and a model developed here using glacio-iostatic loading and unloading implies that the Mt Discovery sites have been above sea-level for approximately the last ~2.7Ma. Given their inferred association with Scallop Hill Formation and faunal similarity to sequences in the nearby ANDRILL drill cores, a Pliocene age is considered most likely. This finding is consistent with previous investigations that indicate a dynamic, sub-polar marine-terminating ice sheet margin in Southern McMurdo Sound during the Pliocene, with periods of open ice shelf free conditions potentially associated with more frequent regional collapse and retreat events of a marine-based ice sheet in the Ross Sea embayment.</p>

Depositional setting and limiting factors of early Late Cretaceous glaucony formation: implications from Cenomanian glauconitic strata (Elbtal Group, Germany)

Cenomanian strata of the Elbtal Group (Saxony, eastern Germany) reflect a major global sea-level rise and contain, in certain intervals, a green authigenic clay mineral in abundance. Based on the integrated study of five new core sections, the environmental background and spatio-temporal patterns of these glauconitic strata are reconstructed and some general preconditions allegedly needed for glaucony formation are critically questioned. XRD analyses of green grains extracted from selected samples confirm their glauconitic mineralogy. Based on field observations as well as on the careful evaluation of litho- and microfacies, 12 glauconitc facies types (GFTs), broadly reflecting a proximal–distal gradient, have been identified, containing granular and matrix glaucony of exclusively intrasequential origin. When observed in stratigraphic succession, GFT-1 to GFT-12 commonly occur superimposed in transgressive cycles starting with the glauconitic basal conglomerates, followed up-section by glauconitic sandstones, sandy glauconitites, fine-grained, bioturbated, argillaceous and/or marly glauconitic sandstones; glauconitic argillaceous marls, glauconitic marlstones, and glauconitic calcareous nodules continue the retrogradational fining-upward trend. The vertical facies succession with upwards decreasing glaucony content demonstrates that the center of production and deposition of glaucony in the Cenomanian of Saxony was the nearshore zone. This time-transgressive glaucony depocenter tracks the regional onlap patterns of the Elbtal Group, shifting southeastwards during the Cenomanian 2nd-order sea-level rise. The substantial development of glaucony in the thick (60 m) uppermost Cenomanian Pennrich Formation, reflecting a tidal, shallow-marine, nearshore siliciclastic depositional system and temporally corresponding to only ~ 400 kyr, shows that glaucony formation occurred under wet, warm-temperate conditions, high accumulation rates and on rather short-term time scales. Our new integrated data thus indicate that environmental factors such as great water depth, cool temperatures, long time scales, and sediment starvation had no impact on early Late Cretaceous glaucony formation in Saxony, suggesting that the determining factors of ancient glaucony may be fundamentally different from recent conditions and revealing certain limitations of the uniformitarian approach.

Eocene facies successions and environments in the Southern Llanos basin, Colombia

This work presents the facies analysis and depositional environment for the Eocene rocks in the southern Llanos Basin (SLLB) and southern Llanos Foothills. Cores and outcrop samples were analyzed by palynology and detrital zircon U-Pbgeochronology. In this paper, we present ages for the facies and two important paleosol markers. The lower member of the Mirador Formation consists of amalgamated sandstones and conglomerates accumulated in a braidad channel belt. The lower Mirador is 33 m thick and early Eocene in the Foothills, whereas in the SLLB, it ist is 22 m thick and middle Eocene in age; it pinches out approximately 33 km to the east. The fluvial facies rests over an unconformity marked by a mature and intensively-weathered paleosol developed over Paleocene, Cretaceous and older rocks to the east. This mature paleosol was dated by U-Pb detrital zircon geochronology as middle to late Paleocene. At the top of the lower Mirador, we describe an interval of sandstones with root casts capped by a thin layer of coal or coaly mudstone. This facies succession evolved as A compound paleosol is a polygenetic soil that marks a change from well-drained conditions under a subaerial vegetation cover to poor-drained conditions of marsh and swamps, which halt vegetation growth, which is incorporated as coal or coaly mudstone, see the section of Facies Successions. At the top of the lower Mirador facies and recorded the cessation of the fluvial system and its stabilization by vegetation. The coal layer marked the posterior rise on the water table and flooding. Detrital zircon U-Pb geochronology dated this compound paleosol as middle Eocene. Above the fluvial facies of the lower Mirador, shallow marine facies deposited during the middle and late Eocene in the Foothills and western SLLB. The marine facies consist in shelf mudstone and shoreface sandstone in a coarsening upward trend. These facies correspond to the C8 member of the Carbonera Formation. The correlative middle Eocene facies to the east of the SLLB are carbonaceous mudstones and coals that were deposited in swamp-marsh and lagoon environments in backshore to coastal-plain environments during the middle Eocene. The fluvial and coastal plain, as well as the marine facies, fossilized an erosional relief less than 50 m high, corresponding to a paleo-landscape. The paleo-landscape was carved at the end of the Paleocene and is capped by the intensely-weathered paleosol indicating subaerial exposition. The paleo-landscape was modeled over Paleocene, Cretaceous, Paleozoic, and basement rocks toward the east and south of the basin. This paleo-landscape lasted until the end of the middle Eocene in the studied area. The Fluvial reservoirs are not continuous but distributed along channel belts composed of channels and braided bars in an NW direction. The marine shoreface reservoirs are distributed as swaths of sandstones in a perpendicular direction to the fluvial belts. These reservoirs have excellent seal rocks above. The plays include fluvial valley sandstones and buried hills of Cretaceous sandstones.

TYPE DESIGNS OF THE PALEOZOIC COMPLEX SECTIONS OF THE EAST EDGE OF THE PERI-CASPIAN DEPRESSION

The present article highlights the features of the geological structure, sedimentation conditions and the influence tectonic evolution factors on the petroleum potential within the eastern edge of the Precaspian basin. According to the features of the geological structure and lithological characteristics of the sedimentary formations of the eastern edge of the Precaspian basin, different facies zones can be distinguished, corresponding to the distinguished structural-formational zones with several types of Paleozoic sections. НЕФТЬ И ГАЗ 2021 1 (121) 7 ГЕОЛОГИЯ Based on the comparison of the Paleozoic sections for the eastern edge of the Precaspian basin it is concluded that collision tectonics was the major factor for sedimentation. Vertical facies succession influenced by tectonics and sea level fluctuations. Carbonate platforms played an important role in the distribution of sedimentary material and controlled the depth of the sea, which influenced on the composition and texture of the rocks. The presence of carbonate platforms was also reflected in the reduced thickness of the Lower Permian sediments, which are less presented within the carbonate platforms stratigraphic section comparing to the adjacent relatively deep-water areas located to the west outside the carbonate platforms. The structure of carbonate platforms was to the largest extent defined by the thrust tectonics and that controlled the distribution of oil and gas fields and potential traps.

Perkembangan Fasies Sedimen Formasi Mamberamo Berumur Miosen Akhir-Pliosen di Cekungan Papua Utara

North Papua Basin is a fore arc basin located in northern coastal of Papua Island. This basin filled by Middle-Upper Miocene turbidite sediment and overlied by Upper Miocene – Quarternary clastic sediment. Upper Miocene – Quaternary clastic sediments (Mamberamo Formation) composed by interbedding conglomerate, sandstone and shale as molasses deposit. A detailed stratigraphic study was performed to identify facies and its association of the Mamberamo Formation to that give a new perspective on the characteristics and development of facies succession of Lower Mamberamo Formation. Result shows that the Lower Mamberamo Formation consists of three facies: A) cross bedding sandstone (subtidal), B) heterolothic silty shale (intra-tidal), C) carbonaceous shale (supra-tidal) deposited on Late Miocen to Plio-Pleistocene during centra range orogeny (syn-orogeny) as molasses deposits.Keywords: Fore arc basin, North Papua Basin, Mamberamo Formation, molasse deposits.

Perkembangan Fasies Sedimen Formasi Mamberamo Berumur Miosen Akhir-Pliosen di Cekungan Papua Utara

North Papua Basin is a fore arc basin located in northern coastal of Papua Island. This basin filled by Middle-Upper Miocene turbidite sediment and overlied by Upper Miocene – Quarternary clastic sediment. Upper Miocene – Quaternary clastic sediments (Mamberamo Formation) composed by interbedding conglomerate, sandstone and shale as molasses deposit. A detailed stratigraphic study was performed to identify facies and its association of the Mamberamo Formation to that give a new perspective on the characteristics and development of facies succession of Lower Mamberamo Formation. Result shows that the Lower Mamberamo Formation consists of three facies: A) cross bedding sandstone (subtidal), B) heterolothic silty shale (intra-tidal), C) carbonaceous shale (supra-tidal) deposited on Late Miocen to Plio-Pleistocene during centra range orogeny (syn-orogeny) as molasses deposits.Keywords: Fore arc basin, North Papua Basin, Mamberamo Formation, molasse deposits.