Detection of large,Holocene earthquakes using diatom analysis of coastal sedimentary sequences,Wellington, New Zealand

Paleoenvironmental reconstructions of three coastal waterbodies in Wellington, New Zealand, reveal that sites were isolated from the sea within the last 7500 years through coseismic uplift and barrier growth. Evidence for coseismic uplift consists of distinct transitions in diatom assemblages representing large changes in relative sea-level or water-table level, commonly in association with sedimentological evidence for catchment disturbance or marine influx. Transitions are abrupt, laterally extensive and synchronous within each waterbody. Amount of change across transition horizons is assessed using quantitative estimates of paleosalinity and waterbody type as proxies for relative sea-level change. Seven transitions involve large paleoenvironmental changes and provide evidence for earthquakes occurring at approximately 5100, 3200 (recorded at two sites), 2300 (recorded at two sites), 1000 cal years BP and 1855 AD. Five other transitions involve smaller paleoenvironmental changes and are considered to be consistent with effects of earthquakes but do not provide independent evidence for earthquake occurrence. These smaller transitions occur at approximately 6800, 3600, 2200, 1000 (coincident with a large transition) and 500 cal years BP. The data refine ages and provide information about the extent and effects of past large earthquakes in the region. These are the first paleoecologically derived earthquake signatures for Wellington and they contribute to the sparse collection worldwide of off-fault sedimentary earthquake records for predominantly strike-slip faults.     

Quaternary hinterland evolution of the active Banda Arc: Surface uplift and neotectonic deformation recorded by coral terraces at Kisar,Indonesia

Coral terrace surveys and U-series ages of coral yield a surface uplift rate of ∼0.5 m/ka for Kisar Island, which is an emergent island in the hinterland of the active Banda arc–continent collision. Based on this rate, Kisar first emerged from the ocean as recently as ∼450 ka. These uplifted terraces are gently warped in a pattern of east–west striking folds. These folds are strike parallel to more developed thrust-related folds of similar wavelength imaged by a seismic reflection profile just offshore. This deformation shows that the emergence of Kisar is influenced by forearc closure along the south-dipping Kisar Thrust. However, the pinnacle shape of Kisar and the protrusion of its metamorphic rocks through the forearc basin sediments also suggest a component of extrusion along shear zones or active doming.Coral encrusts the island coast in many locations over 100 m above sea level. Terrace morphology and coral ages are best explained by recognizing major surfaces as mostly growth terraces and minor terraces as mostly erosional into older terraces. All reliable and referable coral U-series ages determined by MC-ICP-MS correlate with marine isotope stage (MIS) 5e (118–128 ka). The only unaltered coral samples are found below 6 m elevation; however an unaltered Tridacna (giant clam) shell in growth position at 95 m elevation yields a U-series age of 195 ± 31 ka, which corresponds to MIS 7. This age agrees with the best-fit uplift model for the island. Loose deposits of unaltered coral fragments found at elevations between 8 and 20 m yield U-series ages of <100 years and may represent paleotsunami deposits from previously undocumented tectonic activity in the region.     

Late Quaternary river terrace sequences in the eastern Kunlun Range,northern Tibet: A combined record of climatic change and surface uplift

The Kunlun Range, a reactivated orogenic belt, constitutes the northern margin of the Tibetan Plateau. The extreme relief and major landforms of the Kunlun Range are a product of late Cenozoic tectonics and erosion. However, well-developed late Quaternary terraces that occur along the northern slope of the Kunlun Range probably resulted from climatic change rather than surface uplift. The terrace sequences formed in thick Quaternary valley fills and have total incision depths of 50–60 m. Optically stimulated luminescence dating was employed to place time controls on the valley fills and associated terraces. Dating results suggest that periods of significant aggradation were synchronous between different rivers and correspond to the last glacial stage. The abrupt change from aggradation to incision occurred between 21.9 ± 2.7 and 16 ± 2.2 ka, coincident with the last glacial–interglacial transition. Additional terraces developed during the late glacial period and early to middle Holocene. Based on a broader set of chronological data in northern Tibet, at least four regional incision periods can be recognized. Chronological data, terrace elevation profiles, and climate proxy records suggest that these terracing periods were triggered by cool and/or wet climatic conditions. A geometric survey of the riverbed longitudinal profile suggests that surface uplift serves as a potential dynamic forcing for long-term incision. A model is proposed for terrace formation as a response to climatic perturbation in an uplifted mountain range.     

Holocene coastal uplift in the western Pacific Rim in the context of late Quaternary uplift

This paper reviews recent studies of Holocene coastal uplift in tectonically active areas near the plate boundaries of the western Pacific Rim. Emergent Holocene terraces exist along the coast of North Island of New Zealand, the Huon Peninsula of Papua New Guinea, the Japanese Islands, and Taiwan. These terraces have several features in common. All comprise series of subdivided terraces. The highest terrace is a constructional terrace, underlain by estuarine or marine deposits, and the lower terraces are erosional, cutting into transgressive deposits or bedrock. The highest terrace records the culmination of Holocene sea-level rise at ca. 6–6.5 ka BP. Lower terraces were coseismically uplifted. Repeated major earthquakes have usually occurred at ka intervals and meter-scale uplift. The maximum uplift rate and number of terraces are surprisingly similar, about 4 m/ka and seven to four major steps in North Island, Huon Peninsula, and Japan. Taiwan, especially along the east coast of the Coastal Range, is different, reaching a maximum uplift rate of 15 m/ka with 10 subdivided steps. They record a very rapid uplift. Comparison between short-term (Holocene) and long-term since the last interglacial maximum (sub-stage 5e) uplift rates demonstrates that a steady uplift rate (Huon Peninsula) or accelerated uplift toward the present (several areas of Japan and North Island) has continued at least since isotope sub-stage 5e. Rapid uplift in eastern Taiwan probably started only in the early Holocene, judging from the absence of any older marine terraces. Most of the causative faults for the coastal uplift may be offshore reverse faults, branched from the main plate boundary fault, but some of them are onshore faults, which deformed progressively with time.     

Late Cenozoic fluvial dynamics of the River Tana,Kenya, an uplift dominated record

The Late Cenozoic development of the River Tana in Kenya has been reconstructed for its central reach near its confluence with the River Mutonga, which drains the Mount Kenya region. Age control for this system has been provided by K–Ar and Ar–Ar dating. Between 3.21 and 2.65 Ma a major updoming occurred, in relation to the formation of the Kenyan rift valley. The tilting related to this doming has been reconstructed from lava flows that preserve former river gradients. Linear projection of these trends to the current rift valley rim suggests a net updoming of the eastern Gregory Rift valley by at least ∼1 km during 3.21–2.65 Ma. In contrast, since 2.65 Ma the Tana system has been mainly subject to relatively minor epeirogenic uplift. Changing climatic conditions combined with continuing uplift yielded a typical staircase of strath terraces with at least 10 distinct levels. A more detailed reconstruction of the incision rates since 215 ka has been made, by correlating mineralogically fingerprinted volcaniclastic Tana deposits with dated tephras in a lake record. These volcaniclastic sediments were deposited during glacial periods, contemporaneous with lahars. The reconstructed incision rates for the three youngest terraces are ∼0.1–0.2 mm a⁻¹, thus considerably faster than the overall average rate of valley incision since the Mid-Pliocene, of 0.06 mm a⁻¹. A plausible uplift history has been reconstructed using the estimated ages of the Tana terraces and marine terraces on the Indian Ocean coastline. The result suggests an increase in the rate of incision by the River Tana at ∼0.9 Ma, an observation typical in most European river terrace staircases. The reconstructed Late Quaternary development of Tana valley indicates that a similar Quaternary uplift mechanism has operated in both Europe and East Kenya, suggesting a globally applicable process.     

Quaternary and Holocene coastal uplift in Ikaria Island,Aegean Sea

Abstract

Geomorphological, biological and AMS radiocarbon dating provide evidence of an about lm high elevated palaeo-shoreline at the NE coast of Ikaria Island,Aegean Sea, and to a seismic uplift which occurred after AD950-1150 and was probably responsible for damage in an ancient tower. These data are important for several reasons. They provide evidence for a strong earthquake in an island usually assumed aseismic, coastal uplifts and coastal fauna are scarce in this region, while the Late Holocene uplift correlates with a flight of marine terraces of probably Quaternary age, at least up to 40m high. Long-term uplift is not observed at the footwall of a fault bounding a major graben north of Ikaria, it represents a structural puzzle and it may help to shed some light to the evolution of various extensional terranes.     

Neotectonics at the Arabian plate margins

Opening of the Red Sea is accompanied by convergence between the Arabian plate and Eurasia. Regional topography and structure favour gravity glide as the main driving force of plate translation. At the leading edge of the plate, the Zagros Mountains undergo coseismic serial folding which is equivalent to Holocene shortening by ∼20 mm/year and which has led to major episodes of coastal uplift of which the last was ∼1700 years BP. At the Jordan Rift transform, which bounds the Arabian plate on the west, a recurrence interval of ∼1600 years is reported for events of M_L≥5.5. The palaeomagnetic record for the last 3.2 Ma indicates an average spreading rate for the Red Sea of ∼20 mm/year; there is some evidence that hydrothermal activity in the Red Sea is pulsatory, with a period of ∼2000 year, and that it reflects discontinuous spreading. The Holocene neotectonic records of the Zagros, the Jordan Rift and the Red Sea are the product of complex plate interactions and of the accumulation and release of strain in the crust along the plate margins. But they also reflect elastic strain energy storage and release within the Arabian plate, whence parallels in the period of major deformation episodes in the three deforming zones and the apparent discrepancy between the seismic moment predicted by plate kinematics and that recorded in the Zagros. Any associated intraplate deformation, if detected geodetically, would thus help the assessment of seismic hazard.     

Evolution of Ataúro Island: Temporal constraints on subduction processes beneath the Wetar zone, Banda Arc

Ataúro is a key to understanding the late stage volcanic and subduction history of the Banda Arc to the north of Timor. A volcanic history of bi-modal subaqueous volcanism has been established and new whole rock and trace element geochemical data show two compositional groups, basaltic andesite and dacite–rhyolite. ⁴⁰Ar/³⁹Ar geochronology of hornblende from rhyo-dacitic lavas confirms that volcanism continued until 3.3 Ma. Following the cessation of volcanism, coral reef marine terraces have been uplifted to elevations of 700 m above sea level. Continuity of the terraces at constant elevations around the island reflects regional-scale uplift most likely linked to sublithospheric processes such as slab detachment. Local scale landscape features of the eastern parts of Ataúro are strongly controlled by normal faults. The continuation of arc-related volcanism on Ataúro until at least 3.3 Ma suggests that subduction of Australian lithosphere continued until near this time. This data is consistent with findings from the earthquake record where the extent of the Wetar seismic gap to a depth of 350 km suggests slab breakoff, as a result of collision, commenced at ∼4 Ma, leading to subsequent regional uplift recorded in elevated terraces on Ataúro and neighbouring islands.     

Rapid late Pleistocene/Holocene uplift and coastal evolution of the southern Arabian (Persian) Gulf

The coastline along the southern Arabian Gulf between Al Jubail, Kingdom of Saudi Arabia, and Dubai, UAE, appears to have risen at least 125 m in the last 18,000 years. Dating and topographic surveying of paleo-dunes (43–53 ka), paleo-marine terraces (17–30 ka), and paleo-marine shorelines (3.3–5.5 ka) document a rapid, > 1 mm/a subsidence, followed by a 6 mm/a uplift that is decreasing with time. The mechanism causing this movement remains elusive but may be related to the translation of the coastal area through the backbasin to forebulge hinge line movement of the Arabian plate or, alternatively, by movement of the underlying Infracambrian-age Hormuz salt in response to sea-level changes associated with continental glaciation. Independent of the mechanism, rapid and episodic uplift may impact the design of engineering projects such as nuclear power plants, airports, and artificial islands as well as the interpretation of sedimentation and archeology of the area.     

U-series dating of co-seismic gypsum and submarine paleoseismology of active faults in Northern Chile (23°S)

The convergence of the Nazca and South American plates along the subduction margin of the central Andes results in large subduction earthquakes and tectonic activity along major fault systems. Despite its relevance, the paleoseismic record of this region is scarce, hampering our understanding about the relationship between the Andes building and earthquake occurrence. In this study, we used the U-series disequilibrium method to obtain absolute ages of paleoearthquake events associated with normal displacements along the active Mejillones and Salar del Carmen faults in the Coastal Range of the Atacama Desert of northern Chile. The ²³⁰Th–²³⁴U disequilibrium ages in co-seismic gypsum salts sampled along the fault traces together with marine evidences indicate that earthquakes occurred at ca. 29.7 ± 1.7 ka, 11 ± 4 ka and 2.4 ± 0.8 ka. When coupled with paleoseismic marine and radiocarbon (¹⁴C) records in the nearby Mejillones Bay evidencing large dislocations along the Mejillones Fault, the geochronological dataset presented here is consistent with the notion that gypsum salts formed during large earthquakes as a result of co-seismic dilatancy pumping of saline waters along the major faults. Based on maximum observed cumulative vertical offsets in the studied faults, this phenomena could have occurred episodically at a rate in the order of 1:40 to 1:50 with respect to the very large subduction earthquakes during the latest Pleistocene–Holocene period. The results presented here reveal that the U-series disequilibrium method can be successfully applied to date the gypsum salts deposited along faults during seismic events, and therefore directly constrain the age of large paleoearthquakes in hyperarid and seismically active zones.     

Terrace staircases of the River Euphrates in southeast Turkey,northern Syria and western Iraq: evidence for regional surface uplift

We present the first overall synthesis of the terrace deposits of the River Euphrates in SE Turkey, northern Syria, and western Iraq, combining new observations with summaries of data sets from different reaches that had previously been independently studied on a piecemeal basis. The largest number of terraces observed in any reach of the Euphrates is 11, in western Iraq, where this river leaves the uplands of the Arabian Platform. In many other localities not more than 5 or 6 terraces have previously been identified, although we infer that some of these are resolvable into multiple terraces. These terraces are typically formed of gravel, principally consisting of Neotethyan ophiolite and metamorphic lithologies transported from Anatolia. Although older gravels are also evident, most of the Euphrates terrace deposits appear, given the chronologies that have been established for different parts of the study region, to date from the late Early Pleistocene onwards, the cold stages most often represented being interpreted as marine Oxygen Isotope Stages 22, 16, 12, 8, 6 and/or 4, and 2. The formation of this terrace staircase reflects regional uplift of the Arabian Platform. Estimated amounts of uplift since the Middle Pliocene decrease southeastward from almost 300 m in SE Turkey to ∼150 m in western Iraq. Uplift rates increased in the late Early Pleistocene, the uplift estimated since then decreasing from ∼110 m in SE Turkey to a minimum of ∼50 m in the Syria–Iraq border region, then increasing further downstream across western Iraq to ∼70 m. Numerical modelling of this uplift indicates a relatively thin mobile lower-crustal layer, consistent with the low surface heat flow in the Arabian Platform.     

Trenching exposures of the surface rupture of 2008 Mw 7.9 Wenchuan earthquake,China: Implications for coseismic deformation and paleoseismology along the Central Longmen Shan thrust fault

The May 12, 2008, Mw 7.9 Wenchuan earthquake was induced by failure of two of the major faults of the Longmen Shan thrust fault zone along the eastern margin of Tibet Plateau. Our study focused on trenches across the Yingxiu–Bichuan fault, the central fault in the Longmen Shan belt that has a coseismic surface break of more than 200 km long. Trenching excavation across the 2008 earthquake rupture on three representative sites reveals the styles and amounts of the deformation and paleoseismicity along the Longmen Shan fault. Styles of coseismic deformation along the 2008 earthquake rupture at these three sites represent three models of deformation along a thrust fault. Two of the three trench exposures reveal one pre-2008 earthquake event, which is coincident with the pre-existing scarps. Based on the observation of exposed stratigraphy and structures in the trenches and the geomorphic expressions on ground surface, we interpret the 2008 earthquake as a characteristic earthquake along this fault. The interval of reoccurrence of large earthquake events on the Central Longmen Shan fault (the Yingxiu–Beichuan fault) can be inferred to be about 11,000 years according to ¹⁴C and OSL dating. The amounts of the vertical displacement and shortening across the surface rupture during the 2008 earthquake are determined to be 1.0–2.8 m and 0.15–1.32 m, respectively. The shortening rate and uplift rate are then estimated to be 0.09–0.12 mm/yr and 0.18–0.2 mm/yr, respectively. It is indicated that the deformation is absorbed mainly not by shortening, but by uplift along the rupture during the 2008 earthquake.     

Late Holocene marine terraces of the Cartagena region,southern Caribbean: The product of neotectonism or a former high stand in sea-level?

The detailed stratigraphic survey and paleontological study (mollusks, corals, foraminifera and ostracods) of four low-level, ～3 m, marine terrace sections: Punta Canoas, Manzanillo del Mar, Playa de Oro, and Tierra Bomba Island, from the Cartagena region, southern Caribbean, supplemented with 22 radiocarbon dates, reveals that the northern terraces were deposited as parasequences in a clastic depositional system compared to the Tierra Bomba Island succession that was deposited in a carbonate depositional system between ～3600 and ～1700 cal yrs BP. Drier conditions and the southern location of the ITCZ at about 3 ka triggered stronger easterly Trades and more dynamic southwestward sediment drift fed by the Magdalena River mouth, thus promoting the formation of sand spits that ultimately isolated the Cienaga de Tesca coastal lagoon from the Caribbean Sea. Our estimates support the hypothesis that the present position of the terraces is the product of neotectonism rather than a higher 3 ka, sea-level. Upheaval of the terraces varies between ～3.8 mmyr^?1 at Punta Canoas and ～2.2 mmyr^?1 at Tierra Bomba to ～1.5 mmyr^?1 at Manzanillo del Mar and Playa de Oro terraces. Our study corroborates previous contentions on the role of mud diapirism and the dynamics of the Dique Fault as late Holocene upheaval mechanisms.     

Holocene coastal response to monsoons and relative sea-level changes in northeast peninsular Malaysia

Sedimentological, geomorphic, and ground penetrating radar (GPR) data are combined with optically stimulated luminescence data to define the Holocene evolution of a coastal system in peninsular Malaysia. The Setiu coastal region of northeast Malaysia comprises five geological and geomorphic units representing distinct evolutionary phases of this coastline. Estimated marine limiting point elevations indicate deposition of an early aggradational shoreline associated with a sea-level elevation of −0.1 to +1.7 m (MSL_PMVGD datum) between ∼6.8 ka and 5.7 ka, in agreement with previous sea-level studies from the Malay–Thai peninsula. A hiatus occurs in the record between ∼5.7 ka and 3.0 ka, possibly due to a relative sea-level oscillation and shoreline erosion. Long-term relative sea-level fall and possible still-stands created strandplains that are interrupted by aggradational to transgressive paleo-barrier and estuary formation corresponding with brief episodes of RSL rise. Analyses of GPR facies and OSL ages suggest annual clinoform deposition, with geometries dictated by variations in ENSO. These data demonstrate the utility of high resolution studies of coastal facies as useful proxy indicators for paleoclimate studies at subdecadal to millennial time-scales.     

Evidence for millennial-scale climatic events in the sedimentary infilling of a macrotidal estuarine system,the Seine estuary (NW France)

High-resolution sedimentological and rock magnetic analyses from sediment cores collected in the Seine estuary record changes in coastal sedimentary dynamics linked to climatic variations during the late Holocene. Using AMS ¹⁴C and paleomagnetic data we present a first attempt in developing a reliable age model on macrotidal estuarine archives, with a decadal resolution. Correlations between sedimentary successions from the outer Seine estuary document the main sedimentary infilling phases of the system during the last 3000 years. Between 3000 and 1150 cal. BP sedimentary patterns reveal that sequence deposition and preservation are predominantly controlled by marine and tidal hydrodynamics while severe storm events are recorded at ca. 2700 and 1250 cal. BP in the outermost estuary. Conversely, the Medieval Warm Period (MWP; 900–1200 AD) is characterized by a drastic waning of the influence of marine hydrodynamics on sediment preservation. Pronounced episodes of Seine river floods indicate a much stronger impact of continental inputs on sedimentary patterns during this period. The onset of the Little Ice Age marks a diminishing influence of continental inputs while tidal and open marine hydrodynamics again exerted a primary control on the sedimentary evolution of the system during 1200–2003 AD. Coastal sedimentary dynamics as preserved within sedimentary successions appear to have been largely influenced by changes in storminess during the last 3000 years. We have matched the preservation of MWP Seine river floods, as revealed by sedimentological and rock magnetic proxy data, to a prolonged interval of weakened storminess in Normandy permitting the preservation of estuarine flood deposits within a context of reduced coastal erosion in northern Europe. The preservation of sedimentary successions in the Seine estuary is therefore maximal when climate conditions resembled those of the preferred low phase of the NAO on multidecadal timescales such as during 800–1200 AD (MWP). In contrast, increased removal and transport of estuarine sediments occur when winter storm activity greatly intensified over northwestern France. We report four prominent centennial-scale periods of stronger storminess, occurring with a pacing of ～1500 years, which are likely to be related to the last four Bond's Holocene cold events. Our results documenting a close link between coastal sedimentary dynamics, millennial-scale variations in Holocene climate and North Atlantic atmospheric circulation are fairly consistent with other records from Scandinavia, central Greenland and southern Europe.     

Late Quaternary–Holocene evolution of Dun structure and the Himalayan Frontal Fault zone of the Garhwal Sub-Himalaya,NW India

Dun structures are common in the Sub-Himalayan zone of the Himalaya bounded by the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT). They are broad synclinal longitudinal valleys formed as a consequence of the exhumation of the range front of the Himalaya. In the Garhwal Sub-Himalaya, these structures have grown since 0.5 Ma, with the peak activity postdating ∼100 ka. A series of out-of-sequence deformation structures have been identified within the MBT-HFT-bounded Dun structures. They are identified on the basis of geomorphic, post-100 ka stratigraphic, and structural expressions, with activity as young as the early Holocene. To the south of the range front of the Himalaya, uplift has been observed in the Piedmont Zone, with peculiar active tectonic geomorphic expressions. Piedmont sediments of 15–5 ka, determined by Optically Simulated Luminescence (OSL), have been affected by the above uplift. The complete tectonic scenario has been analyzed and an attempt has been made to delineate the sequential evolution of these structures during the post-100 ka period (Late Quaternary–Holocene) in the Himalayan range front.     

Evaluating the role of climate and tectonics during non-steady incision of the Yellow River: evidence from a 1.24 Ma terrace record near Lanzhou,China

The competing roles of bedrock uplift and climatic change in the formation of fluvial terraces remain uncertain. Most of recent studies have attributed terrace formation to climatic changes and held that, even in tectonically active settings, climate variations control cycles of terrace planation and abandonment. Based on field investigations of loess-paleosol sequences, magnetostratigraphy and optically stimulated luminescence (OSL) dating, we develop a new chronology for a spectacular flight of terraces along the Yellow River near Lanzhou, China over past 1.24 Ma. All the terraces are strikingly similar in that they have several meters of paleosol developed directly above fluvial deposits on the terrace treads, suggesting that the abandonment of each terrace due to river incision occurs during the transition from glacial to interglacial climates. However, the ages of terraces cluster in two relatively short time periods (1.24–0.86 Ma and 0.13 Ma – present). During the intervening time between 0.86 Ma and 0.13 Ma, terraces either did not form or were not preserved. We suggest that this record indicates that rock uplift rates varied through time and influenced terrace formation/preservation. Thus, our results demonstrate the utility of deep chronologic records from fluvial terraces for deconvolving the effects of tectonics and climate on fluvial incision.     

Late Quaternary landscape reconstruction and geochronology in the northern Pampas of Buenos Aires province,Argentina

This paper reports the main sedimentary characteristics, soil micromorphology and optically-stimulated luminescence (OSL) ages, and details the pedosedimentary reconstruction, of the Hudson site situated in the northern Pampas of Buenos Aires province. It also provides the OSL chronology and a reinterpretation of previously reported micromorphological features for the nearby site of Gorina. Finally, the stratigraphic records of both sites are compared and the main environmental events discussed in a regional context.At Hudson, situated at a low altitude environment close to the coastal plain, the basal fine-grained paludal deposits were unconformably covered by coastal marine sediments with an OSL age of ca. 128 ka supporting its correlation with the high stand of sea level of marine isotope stage 5e. A paleosol developed on the marine deposits and the underlying paludal sediments. OSL ages suggest that soil development and its subsequent erosion occurred over some period between ca. 128 and 54 ka. Fine sediment accumulation in a paludal environment continued until prior to ca. 23 ka when the accumulation of the uppermost loess mantle started. It continued until the early Holocene when present soil development began. At Gorina, OSL ages suggest that the upper part of the pedocomplex formed at some stage between ca. 194 and 56 ka. Loess then accumulated followed by an erosional phase; loess deposition restarted by ca. 29 ka and continued until the beginning of the Holocene (ca. 9 ka) when the present land surface was established.The stratigraphic and paleoenvironmental differences exhibited by the Hudson and Gorina records result from their contrasting geomorphological settings. The OSL geochronology suggests that the last interglacial (MIS 5) at Hudson is marked by the accumulation of marine deposits (MIS 5e) and the subsequent development of a paleosol. The equivalent soil-forming interval at Gorina is represented by the upper part of the buried pedocomplex. Both at Gorina and Hudson, loess accumulation was dominant especially during MIS 2. Loess accumulation continued during MIS 1 until the early Holocene with apparently somewhat higher sedimentation rates in Hudson. Pedogenesis has been predominant during the rest of the Holocene, resulting in the formation of the surface soil profiles.     

Testing models of mid to late Holocene sea-level change,North Queensland,Australia

Understanding the nature of global ice-equivalent eustatic sea-level changes during the mid to late Holocene is important to our understanding of how ice sheets will respond to future climate change. This study re-analyses the indicative meaning and age control of existing relative sea-level (RSL) data from Cleveland Bay, North Queensland, Australia and presents new RSL data from a foraminifera-based transfer function as a preliminary test of global geophysical models in this region during the mid to late Holocene. The foraminifera-based transfer function produces reliable RSL estimates, consistent through the mid to late Holocene at different locations in Cleveland Bay. Analysis of the combined RSL database reveals that RSL rose above present between 8 and 6.2 ka cal. BP, with the peak of the sea-level highstand c. 2.8 m above present at c. 5 ka cal. BP, remaining relatively stable above +1.5 m from 6.2 until at least 2.3 ka cal. BP, falling to present in the last millennia. This long period of sea level above present in the mid to late Holocene suggests a gradual rather than abrupt end to global ice melt, which must have continued into the late Holocene. This new analysis also shows no evidence for episodic fluctuations within the highstand, although they cannot be entirely ruled out by this study. This study demonstrates that more sea-level data needs to be collected from locations uncontaminated by glacio-isostasy, hydro-isostasy and tectonic effects, in order to better constrain the late Holocene melt histories of the large polar ice sheets.     

Sedimentology of the Rı́mac-Chillón alluvial fan at Lima,Peru, as related to Plio-Pleistocene sea-level changes,glacial cycles and tectonics

The Rı́mac and Chillón Rivers eroded deep valleys on the Lima coastal plain during the Late Miocene (before ca. 5.3 Ma), due to at least 485 m of uplift produced by the Nazca Ridge, combined with a sea level lowstand of around −50 m. The main paleo-Rı́mac channel along the southeastern boundary of the alluvial cone was apparently deflected by the Lima Anticline and reached the sea in the vicinity of Morro Solar, whereas the paleo-Chillón ran largely parallel to the anticline, breaching it to enter the Pacific at present-day Magdalena. These valleys were filled by fine-grained sediments, possibly during marine transgression at 1.7 Ma, which was followed by uplift and regression to below present sea level. Meltwater surges from the Andean Cordillera during subsequent interglacial stades caused an accumulation of coarse, reworked glacial moraine in the Rı́mac and Chillón fans, forming the Lima Conglomerate and drowning the Lima Anticline. The Rı́mac and Chillón Rivers subsequently migrated north and westward, possibly in response to tectonic tilting of the landscape, causing silt and mud to accumulate in abandoned channels along the southeastern boundary of the fan.