En Gedi Core (DSEn) Charts and Plots

Image Description Source
Floating Varve Chronology
and Radiocarbon dates
Migowski et al (2004)
Floating Varve Chronology
and Radiocarbon dates -large
Migowski et al (2004)
Migowski's Date shift Migowski (2001)
Recounted Age-depth plot Neugebauer at al (2015)
Recounted Age-depth plot - large Neugebauer at al (2015)
Correlated Age-depth plots
of DSEn and ICDP 5017-1
Neugebauer at al (2015)
Comparison of paleoclimate proxies
from DSEn to other sites
Neugebauer at al (2015)
Core correlation
DSEn to ICDP 5017-1
Neugebauer at al (2015)
Core correlation
DSEn to ICDP 5017-1 -big
Neugebauer at al (2015)
Thin Section of Jerusalem Quake
showing varve counts
shallow section
Williams et. al. (2012)
Thin Section of Jerusalem Quake
showing varve counts
deep section
Williams et. al. (2012)
Thin Section of Jerusalem Quake
showing varve counts
shallow section - big
Williams et. al. (2012)
Thin Section of Jerusalem Quake
showing varve counts
deep section - big
Williams et. al. (2012)
Table 2a - Seismite Table Migowski et al (2004)
Table 2b - Seismite Table Migowski et al (2004)
Figure 7
Recurrence intervals and
cumulative number of breccias in time
Kagan et al (2011)

En Gedi Core dating ambiguities

The En Gedi Core (DsEn) suffered from a limited amount of dateable material and the radiocarbon dates for the core are insufficiently sampled in depth to produce an age-depth model that is sufficiently reliable for detailed historical earthquake work in the Dead Sea. Migowski (2001) counted laminae in the core to create a floating varve chronology for depths between 0.78 and 3.02 m which was eventually translated into
a year by year chronology from 140 BCE to 1458 CE . The seismites in the "counted interval" were compared to dates in Earthquake Catalogs [Amiran et al (1994), Guidoboni et al (1994), Ben-Menahem (1991), and Russell (1985)]. Relatively minor additional input was also derived from other studies in the region which likely relied on similar catalogs. Some of these catalogs contain errors and a critical examination of where the dates and locations of historical earthquakes reported in these catalogs came from was not undertaken. Migowski (2001) shifted the dates from the under-sampled radiocarbon derived age-depth model to make the floating varve chronology in the "counted interval" match dates from the earthquake catalogs. Without the shift, the dates did not match. This shift was shown in Migowski (2001)'s dissertation and mostly varies from ~200-~300 years. The "counted interval" dates are ~200-~300 years younger than the radiocarbon dates. Some of Migowski's shift was justified. Ken-Tor et al (2001) estimated ~40 years for plant remains to die (and start the radiocarbon clock) and reach final deposition in Nahal Ze'elim. This could be a bit longer in the deep water En Gedi site but 5 to 7.5 times longer (200-300 years) seems excessive. Although uncritical use of Earthquake catalogs by Migowski (2001) and Migowski et al (2004) led to a number of incorrectly dated seismites , the major "anchor" earthquakes (e.g. 31 BC, 1202/1212 CE, 1293 CE) seem to be correct.

Neugebauer (2015) and Neugebauer at al (2015) recounted laminae from 2.1 - 4.35 meters in the En Gedi Core (DsEn) while also making a stratigraphic correlation to ICDP Core 5017-1. Nine 14C dates were used from 1.58 - 6.12 m but samples KIA9123 (inside the Late Bronze Beach Ridge) and KIA1160 (the 1st sample below the Late Bronze Beach Ridge) were discarded as outliers. These two samples gave dates approximately 400 years older than what was expected for the Late Bronze Age Beach Ridge - a date which is fairly well constrained from other studies in the Dead Sea. This left 7 samples distributed over ~4.5 m - an average of 1 sample every 0.65 meters - not a lot. Their DSEn varve count, anchored to an age-depth model derived from these 7 samples, produced an average shift of ~300 years compared to Migowski et al (2004)'s chronology (i.e. it is ~300 years older). Although two well dated earthquakes were available to use as time markers (the Josephus Quake of 31 BCE and the Amos Quake(s) of ~750 BCE), they chose not to use earthquakes as chronological anchors (Ina Neugebauer personal communication, 2015). Instead, they used the Late Bronze Age Beach Ridge as evidenced by discarding the two radiocarbon samples. Using the Beach Ridge as a chronological anchor was likely a good decision as the Late Bronze Age Beach ridge is fairly well dated. Their newly counted chronology produced a paleoclimate reconstruction that aligned fairly well with data from other locations . Although paleoclimate proxies are not necessarily synchronous and suffer from greater chronological uncertainty than, for example, well dated earthquakes, the problem with their recount for our purposes does not lie with their relatively good fit to other site's paleoclimate proxies. That is probably approximately correct. The problem is they calibrated their count to the bottom of their counted interval (Late Bronze Age Beach Ridge) but did not have a calibration marker for the top.

In the En Gedi core (DSEn), the Late Bronze Age Beach Ridge (Unit II of Neugebauer et al, 2015) is found from depths 4.35 to 4.55 m. It's top coincides with the bottom of the recounted interval - far away from the overlap (2.1 - 3.02 m) with Migowski's counted interval. Thus, if there were any problems with the recounted dates (e.g. hiatuses or accumulating systemic errors) as one moved to the top of the recounted interval, they would go unnoticed. Varve counts in the overlapped interval were fairly similar - 583 according to Migowski (2001) vs. 518 according to Neugebauer et al (2015). There wasn't a major discrepancy in terms of varve count interpretation. But, the lack of a calibration point near the top of the recounted interval leaves one wondering if the recounted dates in the overlap are accurate and why Migowski's pre-shifted chronology doesn't correlate well with the reliable parts of the earthquake record.

Neugebauer at al (2015:5) counted 1351 varves with an uncertainty of 7.5% (Neugebauer at al, 2015:8). That leads to an uncertainty of ~100 varves by the time one gets to the top of the recounted interval away from the Late Bronze Age Beach Ridge calibration point. The Beach Ridge itself likely has an uncertainty of +/- 75 years. Add the two together and the uncertainty approaches Migowski's shift. In addition, roughly 15% of the recounted interval went through intraclast breccias (seismites) where the varves were uncountable and the varve count was interpolated with a questionable multiplication factor of 1.61 applied to the interpolated varve count (Neugebauer at al, 2015:5). Migowski et al (2004) also interpolated through the intraclast breccias however in her case she used the interpolation to line up with events out of the Earthquake catalogs.

Unfortunately, Neugebauer at al (2015)'s study did not resolve the uncertainties associated with Migowski's varve counts. Both studies lack a sufficiently robust calibration over the entire depth interval. Dead Sea laminae are difficult to count. They are not nearly as "well-behaved" as they are in the older Lisan formation or in Glacial varves. This was illustrated by Lopez-Merino et al (2016). Their study, which used seasonal palynology to ground truth varve counts, showed that between 1 and 5 laminae couplets (ie varves) could be deposited in a year . This study, undertaken in Nahal Ze'elim, represents a worst case scenario. It is essentially impossible to count varves in Nahal Ze 'elim because the site receives too much fluvial deposition which muddies up the varve count (pun intended) compared to the deeper water site of En Gedi. While the conclusions from Lopez-Merino et al (2016) cannot be generalized to the entire Dead Sea, it does point out that Holocene Dead Sea varve counts need to be calibrated to be used in Historical Earthquake studies. The calibration can come through anchor events such as strong earthquakes and/or clearly defined and dated paleoclimate events, seasonal palynology work (determining the season each laminae was deposited in), and/or dense radiocarbon dating - much denser than what is available from the En Gedi core (DESn). There may also be geochemical ways to calibrate varve counts.

In 2018, Jefferson Williams collected ~55 samples of dateable material from an erosional gully in En Gedi (aka the En Gedi Trench) located ~40 m from where the En Gedi Core (DsEn) was taken in 1997 . This erosional gully was not present when the En Gedi core was taken. It developed afterwards due to the steady drop in the level of the Dead Sea which has lowered base levels and creates continually deeper erosional features on the lake margins. Due to cost, these samples have not yet been dated but lab analysis of this material should resolve dating ambiguities in En Gedi. The samples are well distributed in depth (68 - 303 cm. deep) and can be viewed here in the Outcrop Library. Radiocarbon from the En Gedi Core can be viewed here. In the Google sheets presented on the radiocarbon page for the En Gedi Core, Neugebauer's radiocarbon samples and a reconciliation table can be viewed by clicking on the tab labeled Nueg15.

En Gedi Core (DSEn) Photos

Core Depths were measured from surface. The core was taken about a meter above the Dead Sea level which was ~ -411 m in 1997. In 2011, Jefferson Williams measured the elevation of the surface where the En Gedi Core (DSEn) was taken using his GPS. The recorded elevation was -411 m however GPS is less accurate measuring elevation than it is for Lat. and Long. so this depth measurement should be considered approximate.

Image Description Image Description Image Description Image Description
Composite Core
Sections C1, A2, A3, A4

19-397 cm.
Litholog and
Composite Core

47-325 cm.
Litholog
Entire Core

-30 cm.-1022 cm.
Litholog
Legend
Section C1

19-114 cm.
Section A2

114-196 cm.
Section A3

200-296 cm.
Section A4

300-397 cm.
1458 CE Quake

65-80 cm.
1202, 1212, and 1293 CE Quakes

90-115 cm.
1033 CE Quake

131-143 cm.
Thin Section
A3_3_1a

259.7-269.9 cm.
Thin Section
A3_3_2

271.5-273.7 cm.
Thin Section
A3_3_3

273.5-283.5 cm.
Thin Section
A3_4_1

283.3-293.4 cm.
SEM Image
250x Magnification
Sample EG13

References

Agnon, A., et al. (2006). "Intraclast breccias in laminated sequences reviewed: Recorders of paleo-earthquakes." Geological Society of America Special Papers 401: 195-214.

Kagan, E., et al. (2011). "Intrabasin paleoearthquake and quiescence correlation of the late Holocene Dead Sea." Journal of Geophysical Research 116(B4): B04311.

Kagan, E., et al. (2011). "Correction to “Intrabasin paleoearthquake and quiescence correlation of the late Holocene Dead Sea”." Journal of Geophysical Research: Solid Earth 116(B11): B11305.

Kagan, E. J. (2011). Multi Site Quaternary Paleoseismology Along the Dead Sea Rift: Independent Recording by Lake and Cave Sediments, PhD. Diss. Hebrew University of Jerusalem.

Migowski, C., et al. (2004). "Recurrence pattern of Holocene earthquakes along the Dead Sea transform revealed by varve-counting and radiocarbon dating of lacustrine sediments." Earth and Planetary Science Letters 222(1): 301-314.

Migowski, C. (2001). Untersuchungen laminierter holozäner Sedimente aus dem Toten Meer: Rekonstruktionen von Paläoklima und -seismizität.

Neugebauer, I., et al. (2015). "Evidences for centennial dry periods at ~3300 and ~2800 cal. yr BP from micro-facies analyses of the Dead Sea sediments." The Holocene.

Neugebauer, I. (2015). Reconstructing climate from the Dead Sea sediment record using high-resolution micro-facies analyses, Universität Potsdam. PhD.

Neugebauer, I., et al. (2014). "Lithology of the long sediment record recovered by the ICDP Dead Sea Deep Drilling Project (DSDDP)." Quaternary Science Reviews 102(0): 149-165.

López-Merino, L., et al. (2016). "Using palynology to re-assess the Dead Sea laminated sediments – Indeed varves?" Quaternary Science Reviews 140: 49-66.

Williams, J. B., et al. (2011). "An early first-century earthquake in the Dead Sea." International Geology Review 54(10): 1219-1228.