T54 Cycles of Climate and Layers of Time II: The Scientific Legacies of Roger Y. Anderson and Walter E. Dean, Jr.

Sunday, 15 October 2023
1:30 PM - 5:30 PM
321

DOES SEQUENCE STRATIGRAPHY HAVE THE RESOLUTION TO SERVE AS A CENTURY-SCALE CLIMATE PROXY? CONFIRMATION OF CENTURY-SCALE ‘MICRO’ SEQUENCES IN THE HOLOCENE OF THE DEAD SEA, ISRAEL

Paper number: T54-3
Program: Technical Sessions
Time: 1:55 PM – 2:10 PM

Authors

Abstract

Rises and falls in base level form depositional sequences, and are commonly driven by climate, particularly in lakes. Sequences are perceived to from at time scales of >104 yrs, limiting their utility as high-resolution climate proxies. Sequences are now known to form at millennial time scales, but whether they can form at shorter time scales is suspected, but not previously confirmed. We here confirm that century-scale base-level cycles in the Dead Sea lake, driven by changes in eastern Mediterranean storm tracts, indeed manifest as similarly timed depositional sequences in coast-marginal deposits. We thus present the first confirmation for preservation of century-scale sequences in naturally formed strata. The study maps lithofacies and sequence-stratigraphic surfaces from an ~35 m high outcrop of the post-1500 AD part of the dissected Holocene Nahal Darga falling-stage wedge. We used drone footage of the outcrop to generate a three-dimensional outcrop model, then mapped lithofacies, lapping relationships, surfaces, and systems tracts from images and field observations. We further dated the initiation and completion of systems tracts using carbon 14 dating of bounding surfaces. We compared forest deposits in outcrop to subaqueous ROV footage of adjacent Dead Sea foresets. Lithofacies in foresets and topsets in the Holocene outcrop are replicated by the deposits forming the modern delta and share common origins. Surfaces separating foreset and topset elements of this delta wedge bind systems tracts and record down-step and up-step of the delta shoreface associated with base-level rises and falls. The base-level rises and falls recorded in surfaces and systems tracts mapped in outcrop match known lake-level changes in the Dead Sea in magnitude, timing, and direction. Two complete sequences with full accoutrement of systems tracts and surfaces are mapped in outcrop over the last 1500 years that each begin and end in under a single millennium. These data confirm Medieval (~600 – 1300 AD) and Modern (~1300AD – Modern) century-scale sequences within these strata. These sequences capture the corresponding climate changes that changed lake level, and show the potential of sequence stratigraphy as a high-resolution climate proxy in lake settings.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-395794

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