Evidences for a Paleocene marine incursion in southern Amazonia (Madre de Dios Sub-Andean Zone, Peru)

This article presents new biostratigraphic dating, facies analysis, organic geochemical data and Nd–Sr isotopic provenance from five outcrops of southern Amazonia (MD-85, MD-177 MD-184, MD-255 and MD-256) to document for the first time the presence of a shallow marine ingression in the Paleocene of southern Amazonia basin. The co-occurrence of a selachian assemblage encompassing Potobatis sp., Ouledia sp., and Pristidae indet. with the ostracod Protobuntonia sp. and the charophytes Peckichara cf. varians meridionalis, Platychara perlata, and Feistiella cf. gildemeisteri suggests a Paleocene age for the studied deposits (most likely Thanetian but potentially Danian). Fifteen facies have been recognized and have been grouped into three facies assemblages. Facies association A corresponds to the sedimentary filling of a tide-influenced meandering channel formed in the fluvial–tidal transition zone. Facies association B is related to more distal tidal-flats, little channelized tidal inlets and saltmarsh deposits. Facies association C corresponds to a stressed shallow marine environment such as a bay or a lagoon. The d13CTOC value (- 23.4‰) of MD-184 is enriched in 13C compared to the other samples suggesting the presence of substantial amounts of marine organic matter in MD-184. The d13CTOC values of samples from other outcrops (- 27.3 to - 29.8‰) indicate a mixed organic matter origin, from terrestrial to brackish environments. The analyzed sediments have similar Nd–Sr isotopic compositions as those of the Cenozoic sediments of the Altiplano (eNd(0) values from - 6.2 to - 10.7 and 87Sr/86Sr compositions from 0.712024 to 0.719026) indicating a similar volcanic source. This multidisciplinary dataset documents the presence of a tide-dominated estuary sourced by the proto-Western Cordillera debouching into a shallow marine bay during Paleocene times. This transgression might be explained by subsidence created in response to the proto-Western Cordillera loading. Similar to Miocene marine incursions affecting the Pebas megawetland, Paleogene marine incursions in the Amazonian foreland basin associated with Andean uplift may have played a role in the Neotropical biodiversity dynamics in favoring biogeographical isolation and promoting allopatric speciation for terrestrial organisms

Unusual C35 to C38 alkenones in mid-Holocene sediments from a restricted estuary (Charlotte Harbor, Florida)

Unusual C35 to C38 alkenones were identified in mid-Holocene (8-3.5kyr BP) sediments from a restricted estuary in southwest Florida (Charlotte Harbor). The distribution was dominated by a C36 diunsaturated (ω15,20) ethyl ketone, identical to the one present in Black Sea Unit 2 sediments. Other unus ual alkenones were tentatively assigned as a C35:2 (ω15,20) methyl ketone, a C37:2 (ω17,22) methyl ketone and a C38:2 (ω17,22) ethyl ketone. In late Holocene sediments<3.5kyr BP, the common C37 to C39 alkenones were found. Compound-specific 14C, 13C, and D isotope measurements were used to constrain the possible origin of the alkenones. Conventional radiocarbon ages of alkenones and higher plant-derived long chain n-alcohols indicated no significant difference in age between mid-Holocene alkenones and higher plant n-alcohols. Both alcohols and alkenones were offset vs. calibrated ages of shell fragments in the same sediment core, which suggests they were pre-aged by 500-800yr, implying resuspension and redistribution of the fine-grained sedimentary particles with which they are associated. The hydrogen isotopic (δD) composition (-190‰ to -200‰) of the C37 and C38 alkenones in the late Holocene sediments is in line with values for coastal haptophytes in brackish water. However, the unusual C36 and C38 alkenones from the mid Holocene sediments were enriched in D (by ca. 100‰) vs. the late Holocene alkenones. Also, δ13C values of mid-Holocene alkenones were consistently offset compared with late Holocene alkenones (-21‰ to -22‰ and -22‰ to -23‰, respectively). We suggest that the alkenones in Charlotte Harbor were produced by unknown alkenone-producing haptophyte

Reconstructing Holocene (sub)tropical climate and cyclone variability using geochemical proxies

Anthropogenic greenhouse gas emissions are responsible for a warming trend that cannot easily be reversed. This warming trend is expected to have a large impact on global weather patterns and local environmental conditions, for example by changing precipitation patterns, sea level rise and increasing tropical cyclone activity. Therefore, (sub)tropical coastal regions are expected to be heavily impacted by future climate change. To improve our understanding of the possible consequences of future climate change, paleo-archives can be used, which provide information on past climatic and environmental changes. The aim of the research presented in this thesis was to reconstruct Holocene environmental and climate conditions in (sub)tropical areas, including Florida (USA), the southwest of Japan and Queensland (Australia). In Florida Holocene environmental changes were studied in two estuaries: Tampa Bay and Charlotte Harbor. From mid to late Holocene, environmental conditions changed from fresh/brackish to more marine, which is a consequence of on-going sea-level rise and a relative decrease in terrestrial input. Storm deposits are more frequent in late Holocene sediments, which suggests that the tropical cyclone frequency increased. The impact of human activity in the area was studied in Rookery Bay, an estuary south of Charlotte Harbor. More dynamic and highly variable conditions during the 20th century are thought to reflect the effects of deforestation, canalizations and the construction of roads in the area. In Japan, Lake conditions in Lake Kaiike were reconstructed for the last 2000 years using biomarkers and compound specific hydrogen isotope ratios. Changes in precipitation and runoff, which are related to the intensity of the East Asian monsoon, strongly affected environmental conditions in the lake. The El Niño Southern Oscillation is thought to affect summer monsoon intensity in Asia. A peat core from Northern Queenslands, Australia, was used to test if hydrogen isotopes measured on long chain n-alkanes can be used for the reconstruction of tropical cyclones. For the past 50 years the signal closely follows the number of tropical cyclones that occurred within a 500 km radius. Further down the record however, the sample resolution becomes too low to capture the variability in cyclone-activity. Still, the absence of a clear trend in dD suggests that tropical cyclone frequency and/or intensity did not change appreciably over the last 250 years in Northern Queensland. The results presented in this thesis show that changes in sea level, precipitation and storm activity strongly have affected coastal environmental conditions in the (sub)tropics. If due to human activity coastal areas are altered, this may enhance the effect of natural climate change. Whether the activity of tropical cyclones will change in the future needs further evaluation. Additional paleo-records of storm activity may help to understand the processes involved, and perhaps new approaches like the use of dD to reconstruct precipitation patterns may provide new insights. Not only water temperature but also large-scale changes in the ocean-atmosphere system, will determine whether ongoing climate change will result in more and/or more intense tropical cyclones at specific locations

Reconstructing Holocene (sub)tropical climate and cyclone variability using geochemical proxies

Anthropogenic greenhouse gas emissions are responsible for a warming trend that cannot easily be reversed. This warming trend is expected to have a large impact on global weather patterns and local environmental conditions, for example by changing precipitation patterns, sea level rise and increasing tropical cyclone activity. Therefore, (sub)tropical coastal regions are expected to be heavily impacted by future climate change. To improve our understanding of the possible consequences of future climate change, paleo-archives can be used, which provide information on past climatic and environmental changes. The aim of the research presented in this thesis was to reconstruct Holocene environmental and climate conditions in (sub)tropical areas, including Florida (USA), the southwest of Japan and Queensland (Australia). In Florida Holocene environmental changes were studied in two estuaries: Tampa Bay and Charlotte Harbor. From mid to late Holocene, environmental conditions changed from fresh/brackish to more marine, which is a consequence of on-going sea-level rise and a relative decrease in terrestrial input. Storm deposits are more frequent in late Holocene sediments, which suggests that the tropical cyclone frequency increased. The impact of human activity in the area was studied in Rookery Bay, an estuary south of Charlotte Harbor. More dynamic and highly variable conditions during the 20th century are thought to reflect the effects of deforestation, canalizations and the construction of roads in the area. In Japan, Lake conditions in Lake Kaiike were reconstructed for the last 2000 years using biomarkers and compound specific hydrogen isotope ratios. Changes in precipitation and runoff, which are related to the intensity of the East Asian monsoon, strongly affected environmental conditions in the lake. The El Niño Southern Oscillation is thought to affect summer monsoon intensity in Asia. A peat core from Northern Queenslands, Australia, was used to test if hydrogen isotopes measured on long chain n-alkanes can be used for the reconstruction of tropical cyclones. For the past 50 years the signal closely follows the number of tropical cyclones that occurred within a 500 km radius. Further down the record however, the sample resolution becomes too low to capture the variability in cyclone-activity. Still, the absence of a clear trend in dD suggests that tropical cyclone frequency and/or intensity did not change appreciably over the last 250 years in Northern Queensland. The results presented in this thesis show that changes in sea level, precipitation and storm activity strongly have affected coastal environmental conditions in the (sub)tropics. If due to human activity coastal areas are altered, this may enhance the effect of natural climate change. Whether the activity of tropical cyclones will change in the future needs further evaluation. Additional paleo-records of storm activity may help to understand the processes involved, and perhaps new approaches like the use of dD to reconstruct precipitation patterns may provide new insights. Not only water temperature but also large-scale changes in the ocean-atmosphere system, will determine whether ongoing climate change will result in more and/or more intense tropical cyclones at specific locations

Reconstructing tropical cyclone frequency using hydrogen isotope ratios of sedimentary n-alkanes in northern Queensland, Australia

A peat record from Quincan Crater (Queensland, Australia), spanning the past 200 years, was used to test if hydrogen isotope ratios of leaf wax long-chain n-alkanes derived of higher plants can be used to reconstruct past tropical cyclone activity. Queensland is frequently impacted by tropical cyclones, with on average 1-2 hits per year. The most abundant n-alkanes in the peat are C-29 and C-31. Possible sources for long chain n-alkanes in the peat core are ferns and grasses, which grow directly on the peat layer, and the tropical forest growing on the crater rim. Hydrogen isotope ratios of C-27, C-29 and C-31 n-alkanes vary between -155 and -185 parts per thousand. (VSMOW), with the largest variability in the upper 30 cm of the record. For the period 1950-2000 AD the variability in delta D of C-29 alkanes resembles a smoothed record of historical tropical cyclone frequency occurring within a 500 km radius from the site. This suggests that the high number of tropical cyclones occurring in this period strongly impacted the delta D signal and on average resulted in more depleted values of precipitation. In the period before 1900 AD, the variability in the hydrogen isotope record is relatively small compared to the period 1950-2000 AD. This might be the result of lower variability of tropical cyclones during this time period. More likely, however, is that it results from the increasing age span per sampled interval resulting in a lower temporal resolution. Average delta D values between 1900 and 2000 AD are around -167 parts per thousand, which is similar to average values found for the period between 1800 and 1900 AD. This suggests that on average tropical cyclone frequency did not change during the past 200 years. This study demonstrates the potential of stable hydrogen isotope ratios of long chain n-alkanes for the reconstruction of past tropical cyclone frequency

Reconstructing tropical cyclone frequency using hydrogen isotope ratios of sedimentary n-alkanes in northern Queensland, Australia

A peat record from Quincan Crater (Queensland, Australia), spanning the past 200 years, was used to test if hydrogen isotope ratios of leaf wax long-chain n-alkanes derived of higher plants can be used to reconstruct past tropical cyclone activity. Queensland is frequently impacted by tropical cyclones, with on average 1–2 hits per year. The most abundant n-alkanes in the peat are C29 and C31. Possible sources for long chain n-alkanes in the peat core are ferns and grasses, which grow directly on the peat layer, and the tropical forest growing on the crater rim. Hydrogen isotope ratios of C27, C29 and C31n-alkanes vary between − 155 and − 185‰ (VSMOW), with the largest variability in the upper 30 cm of the record. For the period 1950–2000 AD the variability in δD of C29 alkanes resembles a smoothed record of historical tropical cyclone frequency occurring within a 500 km radius from the site. This suggests that the high number of tropical cyclones occurring in this period strongly impacted the δD signal and on average resulted in more depleted values of precipitation. In the period before 1900 AD, the variability in the hydrogen isotope record is relatively small compared to the period 1950–2000 AD. This might be the result of lower variability of tropical cyclones during this time period. More likely, however, is that it results from the increasing age span per sampled interval resulting in a lower temporal resolution. Average δD values between 1900 and 2000 AD are around − 167‰, which is similar to average values found for the period between 1800 and 1900 AD. This suggests that on average tropical cyclone frequency did not change during the past 200 years. This study demonstrates the potential of stable hydrogen isotope ratios of long chain n-alkanes for the reconstruction of past tropical cyclone frequency

Adjuration before the Judgment : a way of the Prevention against Abuse of Legal Proceedings taken by the Kamakura-Bakufu Government

一　はじめに 二　打越請文 三　懸物押書 (1)　懸物押書に関する立法 (2) 懸物押書の事例 四　その他の《裁許前誓約》 (1) 所務沙汰請文 (2) 雑人訴訟請文 五　《裁許前誓約》の総合的把握 (1) 《裁許前誓約》の内容比較　(2)　成立過程の検討 六　むすびにかえ

Mid- to late-Holocene coastal environmental changes in southwest Florida, USA

During the Holocene, Florida experienced major changes in precipitation and runoff. To better understand these processes, shallow marine sediment cores from Charlotte Harbor (southwest Florida) were studied, covering approximately the past 9000 years. Whole core XRF scanning was applied to correlate different sediment cores on a river to sea transect. Biomarkers were used to identify periods with increased runoff and primary productivity. The mid-Holocene sediments are characterized by a relatively large input of terrestrially derived organic matter, with a maximum in precipitation and runoff around 5 kyr BP. This maximum can be linked to large-scale changes in the hydrological cycle involving shifts of the ITCZ, Bermuda-Azores High and Polar Front. Around 3.5 kyr BP, Charlotte Harbor changed from a runoff-dominated environment to a more oligotrophic and marine setting. Although other studies suggest that, around this time, precipitation in Florida increased, this is not reflected by the Charlotte Harbor records. Possibly, wetter conditions in Florida due to gradual, ongoing, sea level rise in combination with increased precipitation, resulted in accumulation of organic matter on land. Increased sedimentation rates, terrestrial input and primary productivity observed in the upper part of the record are likely a consequence of human impact during the past century. Throughout the record, indications for storm activity can be recognized as coarser grained layers consisting of quartz sands or shell debris. These layers are rare during the mid Holocene, but between 3.2 and 2 kyr BP, their numbers increase, suggesting an increase in tropical cyclone activity in the Gulf of Mexico