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Orbitally paced groundwater in the Ice Age Southwest

Devils Hole cave calcite shows Nevada’s water table rose and fell with glacial cycles for 750,000 years, with a slow long-term drop.

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What cave archive records southwestern US water-table history?

Mammillary calcite in Devils Hole, Nevada, in the Ash Meadows aquifer.

How far back does calcite extend?

Up to 820 ka, beyond the ~650 ka 230Th–U limit, using 234U–U ages.

How many samples were dated in 350–820 ka?

92 processed, five outliers removed.

When does the continuous water-table record begin?

After a brief rise at 746 ± 16 ka (+19.5 m).

How large were pre-350 ka water-table swings?

Up to 15 m amplitude, plus smaller ~20 kyr oscillations.

What long-term decline rate is inferred from +19.5 m at 719 ka to +9.9 m at 438 ka?

3.4 m per 100 kyr.

Does the secular decline continue after 438 ka?

No long-term trend is apparent after 438 ± 14 ka.

When was a major lowstand?

550 ± 15 ka.

How well do 230Th–U and 234U–U ages agree?

For 78 samples (85%) they agree within 2σ; only 4% differ by >1.5× combined uncertainty.

What modern recharge seasonality is cited?

Winter precipitation dominates; summer monsoon is <10% of annual local recharge.

How much extra recharge can glacial highstands imply in a flow model?

Up to +240% increase in groundwater recharge.