USGS Science⌕ Search

Geology topics

Linda E. Heusser

Publications and source records attributed to Linda E. Heusser.

9 recordsLinked to original sources
USGS2022

An 11,300 yr record of paleoclimatology and paleoceanography of the central California coast in a gravity core from Pioneer Seamount

Diatom, pollen, silicoflagellate, and biogenic opal analyses from a 155 cm-long gravity core from Pioneer Seamount, offshore Santa Cruz, California (PS1410-06 GC, latitude 37.3°N, longitude 123.4°W, water depth 2165 m) are compiled for the last ~11,300 years and compared with those of ODP 1019 and TN062-O550 from northern California. The relative abundance record of the subtropical diatom Fragilariopsis doliolus has similar bimodal Holocene patterns in all three cores, suggesting that sea surface temperatures (SST) were lower during the middle part of the Holocene than they were during the later and earlier parts. The relative abundance of coastal redwood ( Sequoia sempervirens ) pollen, a proxy for fog and coastal upwelling, displays stepwise increases in ODP 1019 and TN062-O550 between ~ 4000 and 3000 cal yr. BP, but its relative abundance in PS1410-06 GC increases gradually throughout the past 10,200 yr without any major steps. Similarly, biogenic silica (opal) displays stepwise increases at ~3600 and 2900 cal yr. BP in ODP 1019 and TN062-O550, respectively, whereas opal increases more gradually in PS1410-06 GC during the past 10,100 yr with relatively minor steps at ~3100 and ~2600 cal yr. BP. Together, coastal redwood and opal argue for a more gradual late Holocene increase in coastal upwelling along the coast of central California compared with that off northern California, where onshore-offshore gradients are more distinct.

California↗
USGS2022

Miocene terrestrial paleoclimates inferred from pollen in the Monterey Formation, Naples Coastal Bluffs section, California

We present here a comprehensive record of Miocene terrestrial ecosystems from exposures of the Monterey Formation along the Naples coastal bluffs, west of Santa Barbara, California. Constrained by an updated chronology, pollen analyses of 28 samples deposited between 18 and 6 Ma reflect the demise of mesophytic taxa that grew in a warm, wet environment during the late early and early middle Miocene and the development of a summer-dry/winter-wet Mediterranean climate during the late Miocene. Broadleaf tree pollen from mesophytic woodlands and forests now found in the southeastern United States and China ( Liquidambar , Tilia , Ulmus , Carya ) characterized the Miocene climatic optimum (16.9–14.7 Ma), the middle Miocene climate transition (14.7–13.8 Ma), and the interval up to ca. 13.0 Ma. Subsequently, during the late middle to early late Miocene, between 13.3 and 9.0 Ma, oak woodlands and herbs (Asteraceae, Amaranthaceae, Poaceae) from beach scrub and chaparral increased as ocean temperatures cooled and the climate became drier. Between ca. 8.9 and 7.6 Ma, pine increased mostly at the expense of oak ( Quercus ) and herbs, suggesting a period of increasing precipitation. During the latest Miocene (7.5–6.0 Ma), an increase of herb-dominated ecosystems (chaparral, coastal scrub) at the expense of pine reflects the full development of a summer-dry/winter-wet climate in coastal southern California.

California↗
USGS2018

High-resolution climate of the past ∼7300 years of coastal northernmost California: Results from diatoms, silicoflagellates, and pollen

Piston core TN062-O550, collected about 33 km offshore of Eureka, California, contains a high-resolution record of the climate and oceanography of coastal northernmost California during the past ∼7.34 kyr. Chronology established by nine AMS ages on a combination of planktic foraminifers, bivalve shell fragments, and wood yields a mean sedimentation rate of 103 cm kyr −1 . Marine proxies (diatoms and silicoflagellates) and pollen transported by the nearby Eel River reveal a stepwise development of both modern offshore surface water oceanography and coastal arboreal ecosystems. Beginning at ∼5.4 cal ka the relative abundance of coastal redwood pollen, a proxy for coastal fog, displays a two fold increase suggesting enhanced coastal upwelling. A decline in the relative contribution of subtropical diatoms at ∼5.0 cal ka implies cooling of sea surface temperatures (SSTs). At ∼3.6 cal ka an increase in the relative abundance of alder and oak at the expense of coastal redwood likely signals intensified riverine transport of pollen from inland environments. Cooler offshore SSTs and increased precipitation characterize the interval between ∼3.6 and 2.8 cal ka. A rapid, stepwise change in coastal climatology and oceanography occurs between ∼2.8 and 2.6 cal ka that suggests an enhanced expression of modern Pacific Decadal Oscillation-like (PDO) cycles. A three-fold increase in the relative abundance of the subtropical diatom Fragilariopsis doliolus at 2.8 cal ka appears to mark an abrupt warming of winter SSTs. Soon afterwards at 2.6 cal ka, a two fold increase in the relative abundance of coastal redwood pollen is suggestive of an abrupt intensification of spring upwelling. After ∼2.8 cal ka a sequence of cool-warm, PDO-like cycles occurs wherein cool cycles are characterized by relative abundance increases in coastal redwood pollen and decreased contributions of subtropical diatoms, whereas opposite proxy trends distinguish warm cycles.

California↗
USGS2018

A Holocene record of ocean productivity and upwelling from the northern California continental slope

The Holocene upwelling history of the northern California continental slope is examined using the high-resolution record of TN062-O550 (40.9°N, 124.6°W, 550 m water depth). This 7-m-long marine sediment core spans the last ∼7500 years, and we use it to test the hypothesis that marine productivity in the California Current System (CCS) driven by coastal upwelling has co-varied with Holocene millennial-scale warm intervals. A combination of biogenic sediment concentrations (opal, total organic C, and total N), stable isotopes (organic matter δ 13 C and bulk sedimentary δ 15 N), and key microfossil indicators of upwelling were used to test this hypothesis. The record of biogenic accumulation in TN062-O550 shows considerable Holocene variability despite being located within 50 km of the mouth of the Eel River, which is one of the largest sources of terrigenous sediment to the Northeast Pacific Ocean margin. A key time interval beginning at ∼2900 calibrated years before present (cal yr BP) indicates the onset of modern upwelling in the CCS, and this period also corresponds to the most intense period of upwelling in the last 7500 years. When these results are placed into a regional CCS context during the Holocene, it was found that the timing of upwelling intensification at TN062-O550 corresponds closely to that seen at nearby ODP Site 1019, as well as in the Santa Barbara Basin of southern California. Other CCS records with less refined age control show similar results, which suggest late Holocene upwelling intensification may be synchronous throughout the CCS. Based on the strong correspondence between the alkenone sea surface temperature record at ODP Site 1019 and the onset of late Holocene upwelling in northern California, we suggest that CCS warming may be conducive to upwelling intensification, though future changes are unclear as the mechanisms forcing SST variability may differ.

California↗
USGS2015

Vegetation response to southern California drought during the Medieval Climate Anomaly and early Little Ice Age (AD 800–1600)

High-resolution studies of pollen in laminated sediments deposited in Santa Barbara Basin (SBB) core SPR0901-02KC reflect decadal-scale fluctuations in precipitation spanning the interval from AD 800–1600. From AD 800–1090 during the Medieval Climate Anomaly (MCA) SBB sediments were dominated by xeric vegetation types (drought-resistant coastal sagebrush and chaparral) implying reduced precipitation in the southern California region. Drought-adapted vegetation abruptly decreased at AD 1090 and was rapidly replaced by mesic oak ( Quercus ) woodlands associated with an increased pollen flux into the basin. After a mesic interval lasting ∼100 years, pollen flux and the relative abundance of Quercus pollen dropped abruptly at AD 1200 when the rapid rise of chaparral suggests a significant drought similar to that of the MCA (∼AD 800–1090). This brief resurgence of drought-adapted vegetation between AD 1200–1270 marked the end of the MCA droughts. A gradual increase in mesic vegetation followed, characterizing cool hydroclimates of the Little Ice Age (LIA) in coastal southern California. The presence of xeric vegetation in SBB coincides with major drought events recorded in tree rings and low lake levels elsewhere in California except for the brief drought between AD 1130–1160. Correlative diatom and terrigenous sediment input proxy records from SBB are largely supportive of the pollen record predominantly linking the MCA with drought and La Niña-like conditions and the LIA with wetter (more El Niño-like) conditions. Differences between paleoclimate proxies (pollen, diatoms, and terrigenous sediment) in SBB exist, however, possibly reflecting the temporal and spatial differences in the generation of each proxy record, as well as their individual sensitivity to climate change.

Quaternary International↗
USGS2007

High-resolution climate records of the past 2,400 years from the offshore of northernmost California and central Oregon

High resolution diatom and pollen data from piston core TN062 0550 off northernmost California, and Kasten core WW7710A-26 off coastal Oregon, are compiled for the past 2,400 years. Diatom proxy data for Fall SST from both cores record warm SST's in the intervals from ca. AD 400 to 600, and from ca. AD 1050 to 1300 (later part of the Medieval Warm Period). The intervening AD 650 to 1000 interval, and the post-AD 1350 interval at both sites appear to be relatively cool. Whereas the pollen assemblage from TN062 0550 is dominated by coastal redwood, the pollen assemblage from WW7710A-26 displays alternating moist-dry cycles of alder vs. pine, as well as cycles of western hemlock (typical of the coastal forests of Oregon) vs. coastal redwood (typical of the coastal forests of northern California). Coincidence of intervals characterized by warmer diatom SST with drier pollen assemblages, and those of cooler diatom SST with moister pollen assemblages in the coastal Oregon core, recall the modern-day association of cool PDO with increased precipitation, and warm PDO with decreased precipitation, in the Pacific Northwest.

California, Oregon↗
USGS1987

Subsurface stratigraphy of the eastern Hollister Valley, California

In September 1977, four cores were recovered by shallow auger drilling from Hollister Valley, California, near the Calaveras fault. The wells were drilled to search for evidence that Hollister Valley may have been occupied by a large lake during the late Pleistocene or Holocene. This small valley, near Monterey Bay, may have been dammed by a large landslide on the San Andreas fault (Jenkins, 1973; Herd and Helley, 1977). The cores sampled the first 38 m of sediment below the valley floor, but no lacustrine deposits were found at these sites; a very detailed record to Holocene alluviation in a tectonically subsiding basin.

California↗