Cal YBP Research Articles

Anthropic cut marks in extinct megafauna bones from the Pampean region (Argentina) at the last glacial maximum.

The initial peopling of South America is a topic of intense archaeological debate. Among the most contentious issues remain the nature of the human-megafauna interaction and the possible role of humans, along with climatic change, in the extinction of several megamammal genera at the end of the Pleistocene. In this study, we present the analysis of fossil remains with cutmarks belonging to a specimen of Neosclerocalyptus (Xenarthra, Glyptodontidae), found on the banks of the Reconquista River, northeast of the Pampean region (Argentina), whose AMS 14C dating corresponds to the Last Glacial Maximum (21,090-20,811 cal YBP). Paleoenvironmental reconstructions, stratigraphic descriptions, absolute chronological dating of bone materials, and deposits suggest a relatively rapid burial event of the bone assemblage in a semi-dry climate during a wet season. Quantitative and qualitative analyses of the cut marks, reconstruction of butchering sequences, and assessments of the possible agents involved in the observed bone surface modifications indicate anthropic activities. Our results provide new elements for discussing the earliest peopling of southern South America and specifically for the interaction between humans and local megafauna in the Pampean region during the Last Glacial Maximum.

North American pollen records provide evidence for macroscale ecological changes in the Anthropocene

Recent global changes associated with anthropogenic activities are impacting ecological systems globally, giving rise to the Anthropocene. Critical reorganization of biological communities and biodiversity loss are expected to accelerate as anthropogenic global change continues. Long-term records offer context for understanding baseline conditions and those trajectories that are beyond the range of normal fluctuation seen over recent millennia: Are we causing changes that are fundamentally different from changes in the past? Using a rich dataset of late Quaternary pollen records, stored in the open-access and community-curated Neotoma database, we analyzed changes in biodiversity and community composition since the end Pleistocene in North America. We measured taxonomic richness, short-term taxonomic loss and gain, first/last appearances (FAD/LAD), and abrupt community change. For all analyses, we incorporated age-model uncertainty and accounted for differences in sample size to generate conservative estimates. The most prominent signals of elevated vegetation change were seen during the Pleistocene-Holocene transition and since 200 calendar years before present (cal YBP). During the Pleistocene-Holocene transition, abrupt changes and FADs were elevated, and from 200 to -50 cal YBP, we found increases in short-term taxonomic loss, FADs, LADs, and abrupt changes. Taxonomic richness declined from ~13,000 cal YBP until about 6,000 cal YBP and then increased until the present, reaching levels seen during the end Pleistocene. Regionally, patterns were highly variable. These results show that recent changes associated with anthropogenic impacts are comparable to the landscape changes that took place as we moved from a glacial to interglacial world.

Spatiotemporal Clustering of Paleoseismicity in the Walker Lane, USA: An Extensional Supercycle?

AbstractAt least five surface rupturing earthquakes that occurred during a <300 year time span near Carson City, Nevada, USA form a spatiotemporal cluster of earthquakes similar to those observed on fault systems around the world. These earthquakes exhibit not only temporal clustering behavior, but also have varying rupture boundaries during successive earthquakes. The Carson Range Fault System is a series of east‐dipping normal faults that extend ∼100 km southwards from Reno, Nevada. Previously published paleoseismic and lidar data spanning this system provide evidence of five surface rupturing earthquakes that occurred across the Carson Range Fault System during the last 2,500 years. The three most recent of these earthquakes occurred from 800 to 500 cal ybp, and two other earthquakes occurred on the nearby Incline Village and East Carson Valley faults during this time. Together these five Mw6.4–7.3 earthquakes form a spatiotemporal cluster or supercycle.

Fossil Reefs Reveal Temporally Distinct Late Holocene Lagoonal Reef Shutdown Episodes at Kiritimati Island, Central Pacific

AbstractAn extremely rare example of well‐preserved emergent Holocene fossil reefs exists at Kiritimati Island, central Pacific. Fossil reefs are rich geological archives of paleoenvironmental change. The first paleoecological surveys of two fossil reefs are presented, revealing high coral cover (40–50%) and low diversity (6 genera). Fossil coral ages suggest reefs exhibited disparity in the timing of reef development (4,113 and 1,915 cal yBP) and ecological surveys show different coral compositions (Acropora or Porites dominant), between reefs. Results constrain two discrete episodes of reef shutdown (at 2,905 and 1,705 cal yBP) as lagoonal reefs thrived, and subsequently died off, through the late Holocene. Shifts in physio‐chemical conditions associated with reduced lagoon flushing following storm‐driven changes in atoll rim morphology are argued as the driver for the staged reef die‐off. The findings have implications for interpreting past and future eco‐morphological change on atolls, given projected increases in storminess with climate change.

Paleoindians, paleolakes and paleoplayas: Landscape geoarchaeology of the Tularosa Basin, New Mexico

Karl Butzer was one of the first prehistorians to think about and write about people, ancient and modern, on the landscape. Moreover, as a geomorphologist he knew that past landscapes were as dynamic and varied as they are today — not static entities that formed the backdrop for human activity. That viewpoint is critical in understanding the physical environment faced by humans during the early peopling of the Americas (~13,500 to ~10,000 cal YBP). North America was undergoing rapid environmental changes as the continent was coming out of the last Ice Age. In the southwestern part of the continent large paleolake levels were falling and smaller playa basins were aggrading as the area was occupied by Paleoindian groups such as Clovis, Folsom, and later First Americans. The paleolakes would have provided some resources, but modern gypsum deposits indicate that lake waters were unpotable. Numerous small depressions (playas) scattered around the floor of the Tularosa Basin contain muddy fills that span the Holocene and terminal Pleistocene, indicative of fresher water at least seasonally. Paleoindian sites tend to be clustered around these small basins and along drainages off of the mountains that flank the basin, as well as settings with good viewsheds rather than the main paleolake margins. Paleolakes were dramatic components of the late Pleistocene landscape in the southwest, but likely were not the primary attractions to the First Americans.

Ancient human mitochondrial DNA and radiocarbon analysis of archived quids from the Mule Spring Rockshelter, Nevada, USA.

Chewed and expectorated quids, indigestible stringy fibers from the roasted inner pulp of agave or yucca root, have proven resilient over long periods of time in dry cave environments and correspondingly, although little studied, are common in archaeological archives. In the late 1960s, thousands of quids were recovered from Mule Spring Rockshelter (Nevada, USA) deposits and stored without consideration to DNA preservation in a museum collection, remaining unstudied for over fifty years. To assess the utility of these materials as repositories for genetic information about past inhabitants of the region and their movements, twenty-one quids were selected from arbitrary excavation depths for detailed analysis. Human mitochondrial DNA sequences from the quids were amplified by PCR and screened for diagnostic single nucleotide polymorphisms. Most detected single nucleotide polymorphisms were consistent with recognized Native American haplogroup subclades B2a5, B2i1, C1, C1c, C1c2, and D1; with the majority of the sample set consistent with subclades C1, C1c, and C1c2. In parallel with the DNA analysis, each quid was radiocarbon dated, revealing a time-resolved pattern of occupancy from 347 to 977 calibrated years before present. In particular, this dataset reveals strong evidence for the presence of haplogroup C1/C1c at the Southwestern edge of the US Great Basin from ~670 to 980 cal YBP, which may temporally correspond with the beginnings of the so-called Numic Spread into the region. The research described here demonstrates an approach which combines targeted DNA analysis with radiocarbon age dating; thus enabling the genetic analysis of archaeological materials of uncertain stratigraphic context. Here we present a survey of the maternal genetic profiles from people who used the Mule Spring Rockshelter and the historic timing of their utilization of a key natural resource.

Fringing reef growth over a shallow last interglacial reef foundation at a mid-shelf high island: Holbourne Island, central Great Barrier Reef

Fringing reefs are rare on the mid-shelf of the central Great Barrier Reef, with Holocene development histories established for a few examples. The paucity of reef growth records from mid-shelf fringing reefs has limited opportunities for comparisons with inshore fringing reef growth records to better understand the influence of changes in environmental conditions on reef growth with distance offshore. The long-term development of the mid-shelf fringing reef at Holbourne Island was reconstructed using nine percussion and drill cores that captured the entire Holocene period of reef growth. The cores were chronologically constrained by 16 high-precision 230Th ages. A weathered, Pleistocene reef substrate was U-Th dated as last interglacial (open system age of 131,100 ± 1000 cal yBP) and this provides the underlying foundation upon which the Holocene reef initiated prior to ~7520 ± 20 cal yBP. The last interglacial reef was encountered 5.9 m below the present reef surface and is the shallowest confirmed last interglacial reef in the central GBR region to date. Most of the Holocene reef structure was emplaced within 1000 years of initiation. The chronostratigraphy and contemporary geomorphology of the fringing reef at Holbourne Island preserve evidence of re-working and stripping of the reef structure by cyclones. This evidence includes: 1) an age hiatus in core data of ~3500 years (6238 ± 18 to 2683 ± 10 cal yBP); 2) the abundance of detrital branching coral rubble material within the core facies; 3) the surface elevations and ages of fossil microatolls, which reveal that storm-induced ponding of water during low tidal stages up to 55 cm deep has been active (but intermittent) across the reef flat for at least 600 years and is still active today; and 4) long-standing shingle ridges onshore and modern shingle ridges on the reef flat.

Genetic Discontinuity between the Maritime Archaic and Beothuk Populations in Newfoundland, Canada

Situated at the furthest northeastern edge of Canada,the island of Newfoundland (approximately 110,000km2) and Labrador (approximately 295,000km2) today constitute a province characterized by abundant natural resources but low population density. Both landmasses were covered by the Laurentide ice sheet during the Last Glacial Maximum (18,000 years before present [YBP]); after the glacier retreated, ice patches remained on the island until ca. 9,000 calibrated (cal) YBP [1]. Nevertheless, indigenous peoples, whose ancestors had trekked some 5,000km from the west coast, arrived approximately 10,000 cal YBP in Labrador and ca. 6,000 cal YBP in Newfoundland [2, 3]. Differential features in material culture indicate at least three settlement episodes by distinct cultural groups, including the Maritime Archaic, Palaeoeskimo, and Beothuk. Newfoundland has remained home to indigenous peoples until present day with only one apparent hiatus (3,400-2,800 YBP). This record suggests abandonment, severe constriction, or local extinction followed by subsequent immigrations from single or multiple source populations, but the specific dynamics and the cultural and biological relationships, if any, among these successive peoples remain enigmatic [4]. By examining the mitochondrial genome diversity and isotopic ratios of 74 ancient remains in conjunction with the archaeological record, we have provided definitive evidence for the genetic discontinuity between the maternal lineages of these populations. This northeastern margin of North America appears to have been populated multiple times by distinct groups that did not share a recent common ancestry, but rather one much deeper in time at the entry point into the continent.

History of the great Kanto earthquakes inferred from the ages of Holocene marine terraces revealed by a comprehensive drilling survey

We measured the emergence ages of four marine terraces in the Chikura lowland, which lies to the southeast of the Boso Peninsula, in eastern Japan, to reevaluate the history of the great earthquake occurrences along the Sagami Trough over the past 10,000 years. The dates of the marine terraces are measured via radiocarbon dating of shell fossils obtained from the marine deposits. The sampling method employed in this study collects core samples using a dense and systematic drilling survey, which increased the reliability when correlating shell fossils with marine terraces. In addition, radiocarbon dating was performed with accelerator mass spectrometry, which produces more highly accurate measurements than those measured in previous studies. Moreover, we explored the surface profiles of the terraces with detailed digital elevation model (DEM) data obtained using LiDAR. The maximum emergence ages of the marine terraces were dated at 6300 cal yBP, 3000 cal yBP, and 2200 cal yBP from the top terrace excepting the lowest terrace (which was estimated at AD1703). In addition, another previously unrecognized terrace was detected between the highest and the second terrace in both the dating and the geomorphological analyses and was dated at 5800 cal yBP. The newly obtained ages are nearly a thousand of years younger than previously estimated ages; consequently, the intervals of the great earthquakes that occurred along the Sagami Trough are estimated to be much shorter and more varied than those of previous estimations. This result revises the data used in the current assessment of the probabilities of earthquakes along the Sagami Trough, which could devastate the Tokyo metropolitan area. Furthermore, it demonstrates that the current approach could be a powerful tool to increase the accuracy of assessments of the other areas with depositional marine terraces.

Lithologic controls on valley width and strath terrace formation

Valley width and the degree of bedrock river terrace development vary with lithology in the Willapa and Nehalem river basins, Pacific Northwest, USA. Here, we present field-based evidence for the mechanisms by which lithology controls floodplain width and bedrock terrace formation in erosion-resistant and easily friable lithologies. We mapped valley surfaces in both basins, dated straths using radiocarbon, compared valley width versus drainage area for basalt and sedimentary bedrock valleys, and constructed slope-area plots. In the friable sedimentary bedrock, valleys are 2 to 3 times wider, host flights of strath terraces, and have concavity values near 1; whereas the erosion-resistant basalt bedrock forms narrow valleys with poorly developed, localized, or no bedrock terraces and a channel steepness index half that of the friable bedrock and an average channel concavity of about 0.5. The oldest dated strath terrace on the Willapa River, T2, was active for nearly 10,000years, from 11,265 to 2862 calibrated years before present (cal YBP), whereas the youngest terrace, T1, is Anthropocene in age and recently abandoned. Incision rates derived from terrace ages average 0.32mmy−1 for T2 and 11.47mmy−1 for T1. Our results indicate bedrock weathering properties influence valley width through the creation of a dense fracture network in the friable bedrock that results in high rates of lateral erosion of exposed bedrock banks. Conversely, the erosion-resistant bedrock has concavity values more typical of detachment-limited streams, exhibits a sparse fracture network, and displays evidence for infrequent episodic block erosion and plucking. Lithology thereby plays a direct role on the rates of lateral erosion, influencing valley width and the potential for strath terrace planation and preservation.

Late Holocene Evolution of Currituck Sound, North Carolina, USA: Environmental Change Driven by Sea-Level Rise, Storms, and Barrier Island Morphology

ABSTRACT Moran, K.L.; Mallinson, D.J.; Culver, S.J.; Leorri, E., and Mulligan, R.P., 2015. Late Holocene evolution of Currituck Sound, North Carolina, USA: Environmental change driven by sea-level rise, storms, and barrier island morphology. The Holocene evolution of Currituck Sound, North Carolina, is investigated using geological data and a hydrodynamic model to understand how this depositional basin changed in response to sea-level rise and regional climate patterns. Five depositional units (one Pleistocene and four Holocene) are defined based on geophysical surveys, lithofacies, biofacies, and geochronological data. The earliest Holocene unit (ca. 5000 cal YBP) represents a midsalinity (10–25‰) sand shoal above the transgressive ravinement surface. This unit is overlain, successively, by (1) a freshwater swamp forest deposit, (2) a relatively saline (25–35‰) back-barrier estuarine deposit associated with increased inlet activity, and (3) a mid- to low-salinity (<10‰) deposit that is typical of modern ...

Benthic Foraminifera as Evidence of Paleoenvironmental Changes between 9400 and 8300 cal YBP at the Juréia-Itatins Ecological Station Paleolagoon (SP, Brasil)

ABSTRACT Silva, J.B.; Duleba, W.; Sallun, A.M., and Suguio, K., 2014. Benthic foraminifera as evidence of paleoenvironmental changes between 9400 and 8300 cal YBP at the Jureia-Itatins Ecological Station paleolagoon (SP, Brasil). Many aspects of the Santos Transgression (∼21,227–20,448 to ∼5558–4558 cal YBP) remain controversial, especially before approximately 7800 cal YBP, because of the paucity of data for the Brazilian coast. In this context, benthic foraminiferal assemblages from between 9400 and 8385 cal YBP were analyzed from the S03 core collected at the Jureia-Itatins Ecological Station (JIES) with the aim of clarifying the behavior of the relative sea level along the Brazilian coast during this period. Microfaunal, taphonomical, and morphometric analyses of these microorganisms permitted recognition of eight paleoenvironmental conditions within the lagoon then existing at JIES. There were four phases of conspicuous marine contributions (9400–9338, 9072–8894, 8656–8641, and 8594–8500 cal YBP) wit...

The Duxbury Sunken Forest—Constraints for Local, Late Holocene Environmental Changes Resulting from Marine Transgression, Duxbury Bay, Eastern Massachusetts, U.S.A.

Gontz, A.M.; Maio, C.V., and Rueda, L., 2013. The Duxbury sunken forest—constraints for local, late Holocene environmental changes resulting from marine transgression, Duxbury Bay, Eastern Massachusetts, U.S.A.The present marine transgression has forced geological and ecological zones vertically higher and landward since the late Pleistocene. A recent investigation in Duxbury Bay, Massachusetts, identified 18 Juniperus virginiana tree stumps emergent on an intertidal flat immediately seaward of a small marsh and pond situated between two eroding drumlins. The position of each stump was mapped with global positioning system (GPS), and its elevation with respect to mean lower low water was surveyed. Samples were selected from four stumps with elevations ranging from 2.03 and 0.75 m above mean lower low water for radiocarbon dating. The samples returned calibrated ages between 2219 ± 94 and 2867 ± 79 cal YBP, with the topographically highest sample returning the youngest date. Stump positions suggest a landscape gradient of 1.4 mm/yr between 2000 and 3000 cal YBP. The results are comparable with high-resolution studies of sea level in eastern Massachusetts for the same time period. Comparison of the youngest paleostumps with modern living trees suggests a dramatic change in the landscape gradient, an increase to 1.8 mm/yr. While this is contrary to sea-level studies nearby, it may represent an increase in the energetics of Duxbury Bay and resultant coastal erosion as the bay floods. The site can be used to put the impacts of changing sea-level rates into a landscape evolution framework.

Evidence for Changes in Paleoenvironments along the Lower Cap-Rouge River, Québec (Canada), in Relation to a High Water Stand during the Mid-Holocene Laurentian Transgression

ABSTRACT Verville, J.-F.; Filion, L., and Lajeunesse, P., 2014. Evidence for changes in paleoenvironments along the lower Cap–Rouge River, Quebec (Canada), in relation to a high water stand during the mid-Holocene Laurentian transgression. At the outlet of the Cap-Rouge River, upstream of the Quebec sound on the St. Lawrence north shore, a 5-m-high stratigraphic section was excavated within an urban area, specifically, in a schoolyard located on the 14 m terrace on the east side of the river. Our stratigraphic and high-resolution macrofossil data show that major paleoenvironmental changes occurred along the lower Cap-Rouge River during the mid-Holocene. Macrofossil assemblages indicate that during a low water stand between 6320 and 6230 cal YBP, eastern hemlock (Tsuga canadensis [L.] Carr.) and white pine (Pinus strobus L.) formed mixed stands on the sandy terraces flanking the river. They also indicate that these mesophytic forests shifted to hydrophytic plant communities (eastern larch and aquatic plant...

埼玉県川越市下老袋地区から採取した荒川低地の沖積層ボーリングコア（ＧＳ‐ＫＳＯ‐１）の堆積相と堆積環境

The sedimentary core GS-KSO-1 is obtained in Shimo-oibukuro, Kawagoe City in the Arakawa Lowland, central Japan, which is a part of the research project to construct a depositional model of the latest Pleistocene to Holocene incised-valley fills. The stratigraphy and sedimentary environments have been revealed based on sedimentary facies, grain-size distribution, CNS analysis, and radiocarbon dating. The valley fills in GS-KSO-1 are subdivided as follows; gravelly river deposits, sandy channel fills, floodplain deposits (9000 cal yBP), backmarsh to salt marsh deposits, tidal flat deposits (8000 cal yBP), backmarsh deposits (7000-6000 cal yBP), channel fill deposits and floodplain deposits (6000 cal yBP to present). The age of the maximum flooding surface in the Arakawa Lowland is determined as 8000 cal yBP, which is 1000 to 2000 years earlier than that in the neighboring Nakagawa Lowland. This gap is possibly due to relatively large amount of sediment supply into the Arakawa Lowland.

Cycles of coral reef ‘turn-on’, rapid growth and ‘turn-off’ over the past 8500 years: a context for understanding modern ecological states and trajectories

Human activities threaten reef ecosystems globally, forcing ecological change at rates and scales regarded as unprecedented in the Holocene. These changes are so profound that a cessation of reef accretion (reef ‘turn-off’) and net erosion of reef structures is argued by many as the ultimate and imminent trajectory. Here, we use a regional scale reef growth dataset, based on 76 core records (constrained by 211 radiometric dates) from 22 reefs along and across the inner-shelf of the Great Barrier Reef, Australia, to examine the timing of different phases of reef initiation (‘turn-on’), growth and ‘turn-off’ during the Holocene. This dataset delineates two temporally discrete episodes of reef-building over the last 8500 years: the first associated with the Holocene transgression-early highstand period [∼8.5–5.5 k calibrated years bp (cal ybp)]; the second since ∼2.3 k cal ybp. During both periods, reefs accreted rapidly to sea level before entering late evolutionary states – states naturally characterized by reduced coral cover and low accretion potential – and a clear hiatus occurs between these reef-building episodes for which no records of reef initiation exist. These transitions mimic those projected under current environmental disturbance regimes, but have been driven entirely by natural forcing factors. Our results demonstrate that, even through the late Holocene, reef health and growth has fluctuated through cycles independent of anthropogenic forcing. Consequently, degraded reef states cannot de facto be considered to automatically reflect increased anthropogenic stress. Indeed, in many cases degraded or nonaccreting reef communities may reflect past reef growth histories (as dictated by reef growth–sea level interactions) as much as contemporary environmental change. Recognizing when changes in reef condition reflect these natural ‘turn-on’– growth –‘turn-off’ cycles and how they interact with on-going human disturbance is critical for effective coral reef management and for understanding future reef ecological trajectories.

Re-interpreting Great Lakes shorelines as components of wave-influenced deltas: An example from the Portage River delta (Lake Erie)

Deltas deliver both sediment (bedload sands and suspended load muds) and water to a coastal environment. In the past, deltaic models have emphasized the sandy bedload component constructing a depositional feature that protrudes from the coastline. In contrast, wave-influenced deltas form where river discharge effectively blocks the prevailing longshore drift. The resulting delta is asymmetric, with an extensive strandplain of multiple beach ridges updrift, and fewer beach ridges with wetlands, ponds, and subsidiary bay-head deltas downdrift. In Lake Erie, an analysis of 28 vibracores from the Portage River delta demonstrates significant updrift–downdrift sedimentological differences. Updrift of the delta consists of > 3 m thick gravel-rich sands overlying glaciolacustrine sediment. The deposits are organized into coarsening-upward, progradational shoreline sequences showing facies transitions from lower shoreface to upper shoreface to beachface to backbeach. A 1939 aerial photograph suggests > 15 prograding shoreline sequences were accreted during present lake levels (highstand systems tract), resulting in re-attachment of a bedrock high (Catawba Island) to the mainland. Downdrift of the delta consists of a one progradational shoreline sequence < 1 m thick that overlies peats and glaciolacustrine sediment. The peats have 14C ages between 1616 and 2025 cal YBP, and are interpreted as wetlands that formed during an earlier phase of rising lake levels (lowstand and transgressive systems tracts). The overlying beach ridge was accreted during present lake levels (highstand system tract). The coastal features in this portion of Lake Erie are best understood as components of an evolving wave-influenced delta, the first recognized in the Great Lakes.

Early Holocene Evolution of San Francisco Estuary, Northern California

Abstract Fossil foraminifers (Elphidium excavatum forma selseyensis) recovered from a sediment core from the San Francisco Bay are analyzed for their oxygen isotopic composition. About 8 m of core believed to represent the first 600 years of the current (Holocene) bay's existence at the sample site (from approximately 7650–7050 cal YBP) are highlighted here. This record, deposited at a high, uniform accumulation rate, shows pronounced variation in measured carbonate δ18O, including some of the highest values in the entire Holocene record at the site. It is proposed that this interval records a period during which the fundamental mixing dynamics of the modern estuary became established. We interpret the extremely high δ18O values at about 7400 cal YBP as being indicative of a strongly stratified estuary sampled below its halocline and argue that subsequent details of the isotope record suggest a gradual decrease in water column stratification until conditions qualitatively characteristic of the modern estu...

Distal Run-up Records of Latest Holocene Paleotsunami Inundation in Alluvial Flood Plains: Neskowin and Beaver Creek, Oregon, Central Cascadia Margin, West Coast U.S.A.

Abstract Paleotsunami records in two localities of the central Cascadia margin, Neskowin and Beaver (West Coast, U.S.A., Northeast Pacific Ocean coast), are extended landward to distal flood plain settings. Three paleotsunami sand sheets are correlated to Cascadia subduction zone earthquakes, between 0.3 and ∼1.3 ka in age. One older paleotsunami layer (2960–3220 cal YBP) is apparent in some deeper core sites from the Beaver Creek locality. Marine sand (22%–100%) and marine diatoms (40%–100%) from the distal sand sheets distinguish the catastrophic marine inundations from creek floods. The greatest inundations are correlated to two Cascadia paleotsunami events, #3 at ∼1.3 ka and an older event between ∼2.6 and ∼3.2 ka, based on radiocarbon dating and great earthquake sequence. The best-preserved records are from paleotsunami #3, which reached 4.1 km in overland inundation up the North Beaver flood plain (3 m elevation North American Vertical Datum). At the Neskowin locality, a sand sheet from the #3 paleo...

Rapid Response of a Marine Mammal Species to Holocene Climate and Habitat Change

Environmental change drives demographic and evolutionary processes that determine diversity within and among species. Tracking these processes during periods of change reveals mechanisms for the establishment of populations and provides predictive data on response to potential future impacts, including those caused by anthropogenic climate change. Here we show how a highly mobile marine species responded to the gain and loss of new breeding habitat. Southern elephant seal, Mirounga leonina, remains were found along the Victoria Land Coast (VLC) in the Ross Sea, Antarctica, 2,500 km from the nearest extant breeding site on Macquarie Island (MQ). This habitat was released after retreat of the grounded ice sheet in the Ross Sea Embayment 7,500–8,000 cal YBP, and is within the range of modern foraging excursions from the MQ colony. Using ancient mtDNA and coalescent models, we tracked the population dynamics of the now extinct VLC colony and the connectivity between this and extant breeding sites. We found a clear expansion signal in the VLC population ∼8,000 YBP, followed by directional migration away from VLC and the loss of diversity at ∼1,000 YBP, when sea ice is thought to have expanded. Our data suggest that VLC seals came initially from MQ and that some returned there once the VLC habitat was lost, ∼7,000 years later. We track the founder-extinction dynamics of a population from inception to extinction in the context of Holocene climate change and present evidence that an unexpectedly diverse, differentiated breeding population was founded from a distant source population soon after habitat became available.