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America's 'Dead Sea' Was Once a Vast Freshwater Lake 10 Times Its Size : ScienceAlert (opens in a new tab)

sciencealert.com · 2026-10-04

Short answerEvidenceSource

Short answer

Mixed

Mixed.

One claim goes further than the study. 3 other points were not covered by the paper.

  • 2 supported
  • 1 overstated
  • 3 not covered

Checked against the study summary. The full text wasn't available, so some details couldn't be settled either way.

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Follow the evidence trail
1
2

NewsLink checks it

Mixed

One claim overstates the study. Two of six check out. Three claims the study doesn't address.

  • 2 supported
  • 1 overstated
  • 3 not covered
Open claim evidence
3
Then inspect each claim

Evidence layer

Claim by claim

Each claim gets a verdict. Expand it to see the evidence directly below.

6 claims in this story

Showing all 6 claimsChoose a verdict to focus the list.

Claim 1 of 6OverstatedThe two expanded freshwater or brackish phases are identified as Lake Bonneville and Little Valley, with Lake Bonneville described as freshwater and Little Valley as somewhat brackish.View evidenceHide evidence

As statedabout 30,000 to 16,000 years ago; about 140,000 to 135,000 years ago

Why this verdict

The profile supports the identification and approximate timing of the Bonneville and Little Valley expanded phases. But at abstract depth the paper profile characterizes both as freshwater, deep, expanded lake phases; it does not support the story’s added characterization of Little Valley as “somewhat brackish.”

1

Study evidence

A new basal age for GLAD1-GSL00-4 was obtained from U-series dating of evaporites.

“We update the age model of GLAD1‐GSL00‐4, a 120‐m sediment core recovered by the Global Lakes Drilling (GLAD) project, with new U‐series measurements dating evaporites”
2

Study evidence

The downcore lipid record indicates dominant hypersaline conditions through much of the record, with brief interruptions by expanded freshwater lake phases interpreted as the Little Valley and Bonneville highstands.

“We measure microbial membrane lipid abundances, dialkyl glycerol diethers and glycerol dialkyl glycerol tetraethers (GDGT), to reconstruct salinity over the last two glacial cycles.”
Claim 2 of 6Not coveredThe study identified two periods when the lake was much fresher and much larger, with the lake briefly growing about 10 times larger on two separate occasions.View evidenceHide evidence

As stated10 times larger

Why this verdict

The abstract-level profile supports two brief expanded freshwater lake phases interrupting dominantly hypersaline conditions, identified as Bonneville and Little Valley. However, the specific claim that the lake grew about 10 times larger, and that it was otherwise usually similar in size to today, is not provided in the abstract-level profile, so that magnitude is not verifiable at this depth.

1

Study evidence

The downcore lipid record indicates dominant hypersaline conditions through much of the record, with brief interruptions by expanded freshwater lake phases interpreted as the Little Valley and Bonneville highstands.

“We measure microbial membrane lipid abundances, dialkyl glycerol diethers and glycerol dialkyl glycerol tetraethers (GDGT), to reconstruct salinity over the last two glacial cycles.”
Claim 3 of 6Not coveredThe article says salinity rose again as the lake shrank, and that the transitions from fresh to salty conditions were abrupt in geological terms even if they still took thousands of years.View evidenceHide evidence

As statedthousands of years

Why this verdict

The profile supports a salinity rise after the last pluvial and a transition toward evaporite deposition, with regional comparison to water-balance reconstructions. But the story’s specific framing that the fresh-to-salty transitions were “abrupt in geological terms” while taking thousands of years is not stated in the abstract-level profile, so that temporal characterization is not verifiable here.

1

Study evidence

The downcore lipid record indicates dominant hypersaline conditions through much of the record, with brief interruptions by expanded freshwater lake phases interpreted as the Little Valley and Bonneville highstands.

“We measure microbial membrane lipid abundances, dialkyl glycerol diethers and glycerol dialkyl glycerol tetraethers (GDGT), to reconstruct salinity over the last two glacial cycles.”
2

Study evidence

The salinity rise following the last pluvial agrees with water-balance reconstructions from well-dated lacustrine carbonates.

“The salinity rise following the last pluvial agrees with water balance reconstructions from well‐dated lacustrine carbonates.”
Claim 4 of 6Not coveredThe researchers suggest the larger freshwater phase may have lasted longer because of extra incoming river water, and they connect the ancient shrinking of the lake to warming conditions and modern climate change.View evidenceHide evidence

Why this verdict

The profile includes regional water-balance comparisons and lake expansion/contraction across glacial terminations, but it does not provide abstract-level evidence for the suggested role of extra incoming river water, a direct connection to warming conditions, or modern climate-change implications. The paper profile also notes that GDGTs cannot be used as a temperature proxy in this record, which limits temperature-linked interpretations from these biomarkers.

1

Study evidence

The salinity rise following the last pluvial agrees with water-balance reconstructions from well-dated lacustrine carbonates.

“The salinity rise following the last pluvial agrees with water balance reconstructions from well‐dated lacustrine carbonates.”
2

Study evidence

High and variable salinity in the GLAD1‑GSL00‑4 record precludes use of GDGTs as a proxy for temperature.

“High and variable salinity precludes use of GDGTs as a proxy for temperature.”
Claim 5 of 6SupportedA new study published in Paleoceanography and Paleoclimatology looks back almost 240,000 years into the history of Utah’s Great Salt Lake.View evidenceHide evidence

As statedalmost 240,000 years

Why this verdict

The paper profile says the GLAD1-GSL00-4 core has a revised basal age of 236.3 ka and reconstructs Great Salt Lake salinity over the last two glacial cycles, so describing the study as looking back almost 240,000 years is supported at abstract depth.

1

Study evidence

A new basal age for GLAD1-GSL00-4 was obtained from U-series dating of evaporites.

“We update the age model of GLAD1‐GSL00‐4, a 120‐m sediment core recovered by the Global Lakes Drilling (GLAD) project, with new U‐series measurements dating evaporites”
2

Study evidence

The downcore lipid record indicates dominant hypersaline conditions through much of the record, with brief interruptions by expanded freshwater lake phases interpreted as the Little Valley and Bonneville highstands.

“We measure microbial membrane lipid abundances, dialkyl glycerol diethers and glycerol dialkyl glycerol tetraethers (GDGT), to reconstruct salinity over the last two glacial cycles.”
Claim 6 of 6SupportedResearchers analyzed a 120-meter sediment core from the lake bed and used radioactive dating and microbial chemical signals to estimate how the lake’s salinity changed over time.View evidenceHide evidence

As stated120-meter (394-foot) sediment core

Why this verdict

The profile supports the methodological claim: the study used a 120 m sediment core, U-series dating of evaporites to update the chronology, and microbial membrane lipid abundances to reconstruct salinity. The story’s phrase “radioactive dating” is a reasonable lay description of U-series dating.

1

Study evidence

A new basal age for GLAD1-GSL00-4 was obtained from U-series dating of evaporites.

“We update the age model of GLAD1‐GSL00‐4, a 120‐m sediment core recovered by the Global Lakes Drilling (GLAD) project, with new U‐series measurements dating evaporites”
2

Study evidence

The downcore lipid record indicates dominant hypersaline conditions through much of the record, with brief interruptions by expanded freshwater lake phases interpreted as the Little Valley and Bonneville highstands.

“We measure microbial membrane lipid abundances, dialkyl glycerol diethers and glycerol dialkyl glycerol tetraethers (GDGT), to reconstruct salinity over the last two glacial cycles.”
Then look for missing context

Context layer

What the story left out

Important study details the story did not include.

  • The paper compares its chronology and salinity interpretation with independent regional records, including lacustrine carbonate water-balance reconstructions and Little Valley shoreline tufa U-series dates.

    The supplied story presentation does not mention these independent validation/comparison elements, which are material to how the paper supports and contextualizes its timing claims.

    From secondary_data_comparative_synthesis

  • The paper notes discrepancies and uncertainty in evaporite timing, including disparate halite dates spanning about 90–160 ka and thenardite timing that contrasts with Holocene timing elsewhere in the basin.

    The story does not mention these age-model and basin-heterogeneity caveats, which matter for precise timing of salinity and evaporite transitions.

    From U-series geochronology and age-depth modeling; secondary_data_comparative_synthesis

  • High and variable salinity precludes using GDGTs as a temperature proxy in this record.

    The story connects the findings to warming conditions and modern climate change, but the supplied caveats do not mention the paper’s explicit limitation that GDGTs cannot be used for temperature reconstruction here.

    From proxy applicability assessment

5 things the story did carry across
  • The paper updates the GLAD1-GSL00-4 120 m sediment-core age model using new U-series dates on evaporites, yielding a basal age of 236.3 ka and revised timing of pluvial and evaporite intervals.
  • The paper reconstructs salinity using microbial membrane lipid abundances, including DAGDs and GDGTs, rather than direct ancient salinity measurements.
  • The central salinity result is dominantly hypersaline conditions interrupted by two brief, deep, expanded freshwater lake phases: Bonneville and Little Valley.
  • The revised chronology dates the Bonneville phase to 30.3–16.1 ka and the Little Valley phase to 140.4–134.6 ka, with reported 2σ uncertainties.
  • The paper reports a post-Bonneville salinity rise culminating in thenardite deposition dated to 16.1–12.2 ka and discusses evaporite/halite precipitation after pluvial phases.
Then read the study layer

Study layer

Study at a glance

Scan the study first. Expand only the parts you want to inspect.

Pieces of work

4

Evidence read

study summary

Lead result

ex vivo animal

1Lead resultex vivo animalUpdate the age model of the GLAD1-GSL00-4 Great Salt Lake sediment core using new U-series dates on evaporites, yielding a new basal age and revised timing of pluvials/evaporite phases.U-series geochronology and age-depth modelingExpand

In plain English

The authors update the age model for the 120 m GLAD1-GSL00-4 sediment core using new U-series ages on evaporite horizons, producing a revised chronology with a new basal age of 236.3 ka (2σ = 6.7 kyr) and dated pluvial and evaporite intervals that structure fresh-to-hypersaline transitions across two glacial cycles.

Key findings

  • A new basal age for GLAD1-GSL00-4 was obtained from U-series dating of evaporites.
  • Two freshwater (pluvial) highstands are dated and placed in the revised chronology.
“We update the age model of GLAD1‐GSL00‐4, a 120‐m sediment core recovered by the Global Lakes Drilling (GLAD) project, with new U‐series measurements dating evaporites”
What this piece can’t prove
  • The abstract provides U-series results and age ranges but gives limited detail on sample numbers, analytical protocols, and the specific age–depth modeling approach used.
  • Reliance on evaporite horizons to mark driest intervals assumes those minerals accurately record depositional age and a closed-system behavior; the abstract does not report tests for diagenesis or open-system U-series behavior.

1 further detail could not be confirmed from the summary.

2ex vivo animalReconstruct Great Salt Lake salinity over the last two glacial cycles using microbial membrane lipid abundances (DAGDs and GDGTs) measured downcore, and interpret fresh-to-hypersaline transitions.sedimentary lipid biomarker analysisExpand

In plain English

Downcore quantification of microbial membrane lipids (dialkyl glycerol diethers, DAGDs, and glycerol dialkyl glycerol tetraethers, GDGTs) from GLAD1-GSL00-4 is used to reconstruct salinity changes in Great Salt Lake across the last two glacial cycles, identifying dominantly hypersaline conditions punctuated by two freshwater expanded-lake phases (Little Valley and Bonneville) and later evaporite/halite precipitation.

Key findings

  • The downcore lipid record indicates dominant hypersaline conditions through much of the record, with brief interruptions by expanded freshwater lake phases interpreted as the Little Valley and Bonneville highstands.
  • Two freshwater, deep, expanded-lake phases are identified and dated from the updated core chronology: Little Valley (140.4–134.6 ka, 2σ = 5.5–5.7 kyr) and Bonneville (30.3–16.1 ka, 2σ = 1.0–1.4 kyr).Little Valley: 140.4–134.6 ka (2σ = 5.5–5.7 kyr); Bonneville: 30.3–16.1 ka (2σ = 1.0–1.4 kyr)
“We measure microbial membrane lipid abundances, dialkyl glycerol diethers and glycerol dialkyl glycerol tetraethers (GDGT), to reconstruct salinity over the last two glacial cycles.”
What this piece can’t prove
  • GDGT-derived temperature proxies are not usable here due to high and variable salinity, limiting joint temperature–salinity interpretations from these biomarkers.
  • Some evaporite/halite event ages show disparity across basin records (e.g., halite dates spanning ~90–160 ka), indicating age-model or spatial heterogeneity uncertainties that affect precise timing of salinity transitions.

1 further detail could not be confirmed from the summary.

3secondary dataCompare/validate the revised age model and inferred salinity/evaporite timing against independent regional constraints (e.g., lacustrine carbonates water-balance reconstructions; Little Valley shoreline tufa U-series) and note agreements/discrepancies (e.g., thenardite timing).secondary data comparative synthesisExpand

In plain English

The study cross-compares its revised GLAD1-GSL00-4 age model and inferred salinity/evaporite chronology against independent regional constraints. It reports agreement between the post-pluvial salinity rise and water-balance reconstructions from well-dated lacustrine carbonates, concordance of the age-model assignment with U-series dates for Little Valley shoreline tufa, and a notable discrepancy in thenardite (evaporite) deposition timing (dated here to 16.1–12.2 ka) versus Holocene timing reported elsewhere in the basin.

Key findings

  • The salinity rise following the last pluvial agrees with water-balance reconstructions from well-dated lacustrine carbonates.
  • The age-model assignment agrees with U-series dating of Little Valley shoreline tufa.
“The salinity rise following the last pluvial agrees with water balance reconstructions from well‐dated lacustrine carbonates.”
What this piece can’t prove

4 further details could not be confirmed from the summary.

4otherEstablish that high/variable salinity in this setting precludes use of GDGTs as a temperature proxy in this record.proxy applicability assessmentExpand

In plain English

The authors report that measured GDGT (glycerol dialkyl glycerol tetraether) distributions in the GLAD1‑GSL00‑4 core cannot be used to reconstruct past temperature because the lake experienced high and variable salinity through much of the record, which confounds GDGT-based temperature calibrations. This methodological limitation is stated explicitly in the abstract: "High and variable salinity precludes use of GDGTs as a proxy for temperature."

Key findings

  • High and variable salinity in the GLAD1‑GSL00‑4 record precludes use of GDGTs as a proxy for temperature.
“High and variable salinity precludes use of GDGTs as a proxy for temperature.”
What this piece can’t prove
  • The paper presents this as an interpretive limitation rather than reporting a targeted calibration or sensitivity experiment to quantify the effect of salinity on GDGT-derived temperatures.
  • No numeric salinity thresholds or validation analyses are provided to specify the conditions under which GDGT temperature proxies become invalid.
  • Conclusion is specific to the GLAD1‑GSL00‑4 core and the high/variable salinity conditions reconstructed therein.
Finally, the search trail

Method layer

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Open the paper in Tessa

Fresh to Hypersaline Transitions Across Two Glacial Cycles at Great Salt Lake, Utah

Paleoceanography and Paleoclimatology · 2026

Source record (opens in a new tab)

Why this one

Near certain

NewsLink found the paper. Tessa is where you inspect it deeply.

Papers considered

The selected paper, plus nearby candidates.

Crossref, PubMed, Europe PMC · 16 candidate papers

Selected

Fresh to Hypersaline Transitions Across Two Glacial Cycles at Great Salt Lake, Utah

Paleoceanography and Paleoclimatology · 2026 · Crossref

Source (opens in a new tab)

And 10 more candidates considered.