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Yagur Shutter Ridges

Fig. 11 (left)

Evidence for tectonic activity along the Yagur fault [aka Carmel Fault] during the late Pleistocene and the Holocene. The last 13 ka are marked in yellow.

Fig. 1 (right)

The trace of the Yagur fault [aka the Carmel Fault] between Yoqneam and the Mediterranean

all images from Zilberman et al. (2011)


Caveat

Only one seismic event was detected in the Holocene on the Yagur Shutter Ridges. It was found in the southern shutter ridge but not the northern one. All other detected events were older. The Yagur Fault is also known as the Carmel fault.

Introduction
Abstract

The present study examined the Northern Shutter Ridge (NSR) that developed along the south eastern segment of the Yagur fault, which extends between Yoqneam and Jalame. This shutter ridge represents a left lateral strike slip movement of about 100 m. An additional 400-500 m left lateral displacement can be deduced from the offset of the first order streams that drain towards it.

The alluvial-colluvial sequence, which accumulated between the shutter ridge and the north-eastern slope of Mt. Carmel, was trenched to a depth of 7-8 m (its base was not exposed).

This sequence, which dated between 200 ka and 100 ka, overlies a hard well cemented gravel unit that paves the trench bottom and the nearby Carmel slope. It is assumed that this gravel unit was deposited on the bottom of a channel that flowed along the rock barrier to the north. A change in the depositional environments triggered a slow accumulation of colluvial-alluvial clay-rich sediments beyond the shutter ridge. The slow accumulation process was interrupted by sporadic debris flow events that transported coarse gravel from remote slopes to the small dammed basin.

There is no evidence for young deformation in the sedimentary fill of the small basin, however, the lithological nature of this clay-rich sediment can prevent the preservation of any sedimentary or tectonic structure.

We conclude that the shutter ridge developed during the end of the Middle Pleistocene or the early late Pleistocene and gradually filled during the late Pleistocene, until the rock barrier was breached.

The results of the present study were combined with additional data obtained from previous studies carried out along the Yagur fault to conclude that it was continuously active throughout the late Pleistocene. Circumstantial evidence for Holocene activity were found so far only in the Southern Shutter Ridge, but it must be noted that most of the Holocene sequence along the fault trace is disturbed by anthropologic activity and therefore, if there was evidence for young activity it was probably obliterated.

Based on general geological consideration as well as new data obtained from paleoseismic and other studies, we recommend treating the Yagur fault as an active fault.

Geographic setting of the Shutter Ridges

Fig. 2

The location of the two studied shutter ridges (marked by red ellipses). The main faults are marked by yellow dotted lines and the direction of the lateral displacement is marked by yellowish arrows.

Zilberman et al. (2011)


The North Shutter Ridge (NSR) is located in the outlet of a small second order stream, some 2.5 km north of the Southern Shutter Ridge (SSR) (Zilberman et al., 2006; Ashkar Halak, 2009). The blocking ridge is some 100 m long, built of a northward-tilted Turonian limestone sequence. The southern edge of the ridge was breached by the stream forming a V-shaped outlet with a shallow alluvial fan stretching to the north. The tributaries upstream of the blocked channels show a westward deflection from a straight northward flowing course as expected on the steep northern slopes of Mt. Carmel.

This deflected course is attributed to the left lateral displacement by the Yagur fault (Achmon, 1986, Gluck, 2002, Ashkar-Halak, 2009). The offset decreases from about 500 m in the eastern tributary, to about 150 m in the western tributary.

The shutter ridge is a part of a 300-400 m wide shear zone, characterized by shattered rocks and dense vertical fracture system (Fig. 2). It rises some 20 m above the alluvial plain that extends from its foot northward toward the Qishon River (fig. 3).

Fig. 3

A southward view at Mt. Carmel showing the blocked and displaced fluvial system. The shear zone of the Yagur fault is marked by two black dotted lines. The outlet of the main channel is offset by ~500 m in relation to the confluence point of its southern tributaries. The shutter ridge reflects an additional offset of ~100 m.

Zilberman et al. (2011)


The Carmel Fault (aka the Yagur fault)


Figure 1

Location map. The Yagur and the Nesher faults are displayed on the 1:200.000 geological map by Sneh et al. 1998

Zilberman et al. (2008)


The Carmel fault runs along an ancient suture line that separate between two different geological provinces: The northern province, which includes northern Israel and Lebanon is characterized by a thin crust (about 23 km) while the southern province that includes the microplate of Israel and the Sinai peninsula (Salamon et al., 1996), has a thicker crust (more than 30 km) (Ginzburg and Folkman, 1980; Ben Avraham and Ginzburg,1990; Hofstteter et al, 1991).These two provinces differ in their structural character, seismic activity and style of topography (Achmon and Ben Avraham, 1997). This tectonic boundary is suggested to be a regional important structure since the Palaeozoic (Ben Avraham and Ginzburg, 1990), The Jurrasic (Derin, 1974), or Cretaceous (Kafri and Folkman, 1981).

The Carmel tectonic line shows a relatively high seismic activity (Ben Menhaem and Aboody, 1981; Shapira and Feldman, 1987, VanEck and Hofstteter, 1990), and is considered by De Sitter (1962), Freund, (1970), Garfunkel et al., (1981), and Hofstetter et al. (1996), among others, as a seismically active branch of the Dead Sea Transform (DST).

The origin and the age of the Carmel fault is a source of controversy. Some connected its origin to the Dead Sea Rift during the Middle Miocene and considered it as a left lateral strike slip that branches from the DST and transfers part of the sinistral movement to the Levant continental margin (De sitter, 1962, Fruend, 1970, Rotstein et al., 1993; Schattner et al., 2006). Others suggested that it predated the DST and was established during the opening of the Red Sea as part of the NW oriented "Erythrean" tectonic system (Picard, 1931; Picard and Kashai, 1958; Horowitz, 1979; Schattner, 2005).

The tectonic domain of the Carmel fault and its sense of displacement are also under debate. Ron (1984) and Ron and Eyal, (1985) concluded that the structure of the Galilee and the Carmel regions was developed under a Miocene stress field of E-W σHmax and Pliocene to recent N-S extensional stress field. A later work (Ron et al., 1990) explained the Carmel structure as a result of a uniform stress field where σHmax is in E-W direction.

Matmon et al., (2003) suggested that the structures of the Lower Galilee, Yizre'el Valley and the Carmel have developed since the Early Miocene under continuous extensional domain. This model is in contrast to the sinistral movement of some of 3-4 km, which was estimated for the Carmel fault by Arad (1965), Fruend, (1970), and Rotstein et al., (1993), of which about 300 m are considered by Achmon (1986) as a young motion, which displaces stream channels.

Sinistral offset of alluvial fans and streams was described by Achmon (1986) and Gluck (2001) from the northeastern mountain front of the Carmel. A left lateral component also characterizes some of the recent earthquake epicenters detected along the northwestern segment of the Carmel tectonic line (Hofstteter et al., 1996). The focal plane solution of the present seismic activity of the fault is therefore in accord with the model suggested by De-Sitter (1962), Fruend (1970) and Schattner (2006) to the entire fault system along the Carmel Line and the Carmel Block. However, relocation of earthquakes epicenters that occurred in this seismogenic zone since 1984 by Shamir, (2006), found a diffuse distribution of the epicenters, with the moderate activity taking place mostly north-east of the mapped fault line.

The Carmel fault crosses the down town of Haifa, and runs just south of the chemical industry area of the Haifa bay, and therefore is a potentially source of a seismic hazard for this highly populated region.

The aim of the present research was to study the young (Pleistocene-Holocene) paleotectonic activity in selected sites along the Carmel fault system by conducting a paleoseismic analysis.

Two tectonic elements were analyzed in the present stage
  1. The Nesher fault, which is a branch of the Carmel Fault
  2. The N-S oriented segment of the Carmel Fault running between Yoqneam and Jalame (Fig. 1).
In the first site we trenched a young alluvial fan that was deposited on the fault trace; in second site we dated sediments that were accumulated beyond a Shutter Ridge, which formed by a sinistral displacement along the Carmel Fault (Achmon, 1986; Ashqar et. al., 2006: Ashqar et al., in prep.).

Maps, Aerial Views, Plots, Trench Log, and Photos
Maps, Aerial Views, Plots, Trench Log, and Photos

Location Map / Geologic Map


Figure 1

Location map. The Yagur and the Nesher faults are displayed on the 1:200.000 geological map by Sneh et al. 1998

Zilberman et al. (2008)


Aerial Views

  • Fig. 1 Yagur Fault Trace
    Fig. 1

    The trace of the Yagur fault [aka the Carmel Fault] between Yoqneam and the Mediterranean

    Zilberman et al. (2011)
    from Zilberman et al. (2011)
  • Fig. 2 Yagur Shutter Ridges
    Fig. 2

    The location of the two studied shutter ridges (marked by red ellipses). The main faults are marked by yellow dotted lines and the direction of the lateral displacement is marked by yellowish arrows

    Zilberman et al. (2011)
    from Zilberman et al. (2011)
  • Fig. 3 Stream Displacement
    Fig. 3

    A southward view at Mt. Carmel showing the blocked and displaced fluvial system. The shear zone of the Yagur fault is marked by two black dotted lines. The outlet of the main channel is offset by ~500 m in relation to the confluence point of its southern tributaries. The shutter ridge reflects an additional offset of ~100 m.

    Zilberman et al. (2011)
    on Yagur Shutter Ridges from Zilberman et al. (2011)
  • Yagur Shutter Ridges
    Yagur Shutter Ridges

    click on image to explore this site on a new tab in Google Earth
    in Google Earth
  • Yagur Shutter Ridge
    Yagur Shutter Ridge (approx. location)

    click on image to explore this site on a new tab in govmap.gov.il
    on govmap.gov.il

Plot of Seismic Activity


Fig. 11

Evidence for tectonic activity along the Yagur fault during the late Pleistocene and the Holocene. The last 13 ka are marked in yellow.

Zilberman et al. (2011)


Southern Shutter Ridge Trench

Annotated Aerial View


Fig. 11

Tectonic and morphologic elements in the study area

Zilberman et al. (2007)


Columnar sections of the Back-Barrier Terrace (with OSL Ages)


Fig. 15

Columnar sections of the Back-Barrier Terrace (From Ashqar et al in prep.)

Zilberman et al. (2007)


Northern Shutter Ridge Trench

Aerial View


Fig. 6

A westward view of the trench excavated across the flat terrace that accumulated between the shutter ridge and the slopes of Mt. Carmel.

Zilberman et al. (2011)


Trench Log


Fig. 7

The log of the trench excavated across the back-barrier terrace of the NSR.

Zilberman et al. (2011)


Aerial View


Fig. 8

A southward view at the trench. In the front – the white shutter ridge. Most of the fill is the reddish-brown unit 4, covered by dark brown younger colluvium. The white boulders (marked by the arrow) are part of the coarse facies of unit 4.

Zilberman et al. (2011)


Inside the Trench


Fig. 9

The coarse facies of unit 4. The size of the boulders (marked in yellow color) is up to 70 cm and they are mostly matrix supported.

Zilberman et al. (2011)


OSL Dating Results


Table 1

Results of OSL dating in the trench

Zilberman et al. (2011)


Photos

  • Fig. 4 North Shutter Ridge
    Fig. 4

    The North Shutter Ridge . The blocked stream is marked by a blue line. The outlet of the stream, which is incised in the southern margin of the ridge, is hidden by the vegetation.

    Zilberman et al. (2011)
    from Zilberman et al. (2011)
  • Fig. 5 Shattered rocks
    Fig. 5

    Shattered rocks built of cemented breccia. The exposed surface is a north- facing fault plain of the Yagur fault shear zone.

    Zilberman et al. (2011)
    from Zilberman et al. (2011)

Master Seismic Events Table
Master Seismic Events Table

Discussions
The Southern Shutter Ridge

Introduction

A shutter ridge is a barrier formed across a stream-valley by tectonic activity, which blocks the downstream flow (Burbank and Anderson, 2001). The barrier can be formed by vertical (normal or reverse) or lateral displacement. The blocked stream can change its course and flow around the barrier or it can fill the reservoir formed behind the tectonic dam by sediments that accumulate up to the top of the barrier and then overflow it.

Two sites in streams that were blocked by shutter ridges were found along the Carmel fault (Fig. 1), both located along the N-S oriented segment that extends between Yoqneam and Jalame (Achmon, 1986, 1991; Ashqar, 2006). This segment was considered by Achmon (1986) a restraining bend, associated with intensive deformation and block rotation. He estimated that the shutter ridges were formed due to young lateral offset of about 300 m.

The shutter ridge selected for the present study is located at an outlet of a small stream, about two km long (coords. 20950/23205). It separates between the upper reach of the stream channel that incised in the steep northeast-facing slopes of the Carmel and its alluvial fan, which was deposited north of the slope margins (Fig. 11).


Fig. 11

Tectonic and morphologic elements in the study area

Zilberman et al. (2007)


Geological Background


Fig. 11

Tectonic and morphologic elements in the study area

Zilberman et al. (2007)


The northeastern slope of the Carmel Mt. is composed in the study area of a NE tilted Turonian sequence. This sequence builds unstable slopes with abundant landslides, and in fact it is difficult to find a slope that was not disturbed by some kind of mass-movement.

The Carmel fault crosses the eastern margins of the Carmel, forming a shear zone several hundreds meters wide (Achmon, 1986). The Shutter ridge is composed of eastward tilted bedded limestone, which forms a narrow ridge that extends several hundreds meters to the south of the stream (Fig. 11). A flat alluvial terrace covered by colluvium and soils, developed along the western backside of the ridge (Fig. 12). In the west this terrace is bounded by a fault that runs along the Carmel slope (Fig. 13). Additional faults occur further to the west on the steep slopes.

A large morphological cirque was formed by landslide scar between altitude 200 and 300m in the upper stream valley (Fig. 11). This landslide blocked the stream channel and formed a series of knick points expressed as dry waterfalls. This barrier also prevented alluvial materials from reaching the down stream channel and therefore enhanced an incision regime near the stream outlet.

Fig. 12 (left)

The back-barrier terrace south of the stream valley

Fig. 13 (right)

The fault plane that forms the western boundary of the Back Barrier Terrace

both from Zilberman et al. (2007)


Discussion

In order to examine the possibility of tectonic activity along the Carmel fault, the thick sequence, which was accumulated beyond the shutter ridge, must be explained. It might be argued that this accumulation is not necessarily a result of stream blockage, but it may also reflect a negative balance between water discharge and sediment yield (Low water/sediment ratio) from the drainage basin (Schumm, 1977). Such situation could be related to a climatic deterioration or anthropogenic activity resulted in destroying the forest and intensive slopes erosion. However, in such case a similar sediment accumulation should have been found also in other streams along the Carmel Mt. and so far such accumulation along other streams, is not known.

Hence, the basic hypothesis in our interpretation is that in order to accumulate such a thick sequence of alluvium in a high gradient stream (about 11%), we must assume some disturbance to the down stream transport of the alluvial sediments.

We did not find any clear evidence to a morphological-sedimentological barrier such as debris flow or landslide near the outlet of the stream, and so the rocky shutter ridge is left as the only possible barrier.

The stratigraphic sequence of the higher terrace reflects two different sediment sources: The older part is composed of materials derived mainly from exposures of soft rocks and pyroclstic units. The younger sequence is composed mainly of reworked Terra Rossa soil with some gravel derived mainly from hard carbonate rocks (dolomite and limestone).

The age of these two alluvial-colluvial units and their field relations, indicate two different periods of accumulation separated by an incision event. The older unit was accumulated slowly during more than 100ky, starting before some 146ky and continued until 22ka-27ka. This period was terminated by incision of the stream up to the present level of the stream channel, so the accumulation of the younger unit started before some 3.5 ky from the same level as unit 1. The second accumulation phase was short and terminated before 2.3 ky.

The volcanic gravels found in unit1 raise a question concerning their source, because there are no exposures of volcanic rock mapped so far in the drainage basin of the studied stream (Segev in prep.). Such rocks are exposed in a drainage basin of an adjacent stream further to the south. Hence, the existence of such gravel in the study site can be explained in several ways:
  1. volcanic rocks were exposed in the past in the drainage system of the studied stream but were covered later by landslides.

  2. Unit 1 was tectonically displaced to its present site from an alluvial fan in the south.

  3. The gravels were transported to their present site by a north flowing stream that drained volcanic outcrops in the south.
So far we do not have enough data to decide which hypothesis should be adopted and additional field work is required in order to clarify this problem.

The incision event that separates between the depositions of the two alluvial units reflects a major change in the hydrology of the stream, which prevented alluvial materials from the upper drainage basin to reach its outlet. It is suggested that this change is related to a large landslide that formed a barrier and a high waterfall a few hundreds of meters upstream. The age of this landslide should be younger than the age of the top of the older unit, e.g. 23.5ka.

Hence, we suggest that the thick sequence (8 m) found behind the shutter ridge reflects two episodes of stream blockage, due to a northward displacement of the shutter ridge.

The barrier which was formed in the younger episodes (e.g. about 4ky BP) was several meters high and triggered rapid accumulation of alluvial and colluvial sediments. The stream broke through the shutter ridge not earlier than 2.3 ka and incised rapidly to its present level.

Additional evidence for young tectonic activity is manifested by the Stream Outlet Terrace, which reflects accumulation of coarse alluvium in a stream valley that surrounded the shutter ridge. This terrace, which has a sub horizontal upper surface, indicates a low-relief valley bottom, which is not in accord with the downstream abandoned steep alluvial fan. There is a sharp gradient change between the terrace and the ancient abundant alluvial fan further to the east and it seems that it is hanging above it. Such relations could have been formed by uplift of the terrace in relation to the eastern margins of the Carmel ridge. We do not know yet what is the age of this terrace but, it is clear that it supplies time-constraint on the stream blocking.

The morphological relations between the old and the present alluvial fans of the stream are also typical to an uplifting terrain. The apex of the present active alluvial fan is located at the margins of the old fan, indicating a migration of the base level to the north as a result of uplift of the old fan together with the mountain front (Denny, 1967; Bull., 1977).

Conclusions

Two groups of evidence are presented here for young tectonic activity along the Yoqneam-Jalame segment of the Carmel Fault.
  1. Young uplift of the mountain front is manifested by the hanging position of the Outlet Terrace in relation to the old alluvial fan of the stream, and the development of recent telescopic alluvial fan in the northern margin of the old abandoned one

  2. Two periods of stream blockage, probably by horizontal displacement of a rock slab along the Carmel Fault, were identified so far. The first period is associated with slow accumulation of sediments beyond the shutter ridge, which lasted between 146 ka and 24.5ka. The second period was associated with fast accumulation, which lasted between 3.5 ka and 2.3 ka. A period of stream incision separated between these two periods of sedimentation.
If we relate the deposition/incision processes in this small stream to tectonics alone, we may reach the conclusion that the stream was blocked in the first time at the beginning of the late Pleistocene and again in the Late Holocene. For our purpose it is more important to evaluate the tectonic origin of the second young event and to eliminate other causes that might result in a similar reaction of the fluvial system.

In order to achieve this goal we must date the entire sequence of the Inner Terrace, the sequence of the Outlet Terrace and the abandoned alluvial fan. We also have to conduct a more regional research in order to find if accumulation of thick alluvium also occurred in other streams, which drain the northern mountain front of the Carmel.

Summary

The present study show evidence for continuous tectonic activity along the Nesher fault during the Late Pleistocene, but it seems that during the Holocene this branch of the Carmel fault was stable. Tectonic activity also occurred during the Late Pleistocene along the Yoqneam-Jalama segment of the Carmel fault but here there are also indications for Middle to Late Holocene activity.

We intend to continue our study in the two sites in order to collect additional data that we hope will clarify the tectonic picture. We will date the upper part of the sequence of the Back-Barrier Terrace and will try to establish a better chronosequence in this site. We will trench the southern part of the alluvial fan in the Nesher fault site in order to clarify the relations between the fault and the various sedimentary units, and will try to obtain a better age constrain on the tectonic activity.

The Northern Shutter Ridge

Summary and Discussion

The tectonic activity represented by the NSR, reflects only part of the left-lateral displacement along the Yagur fault. The amount of lateral displacement at this site is at least 100 m (the length of the shutter ridge), but this amount should be added to the 500 m offset of the southern first order channel of the drainage system that was blocked by the Shutter ridge (Achmon, 1986: Ashkar-Halak, 2009). The offset represented by the three streams that drained toward the shutter ridge seems to decline northward (Fig 2). This change can be attributed to the width of the shear zone in this area (almost 400 m), which raises the possibility that the lateral movement splits between several branches of the Yagur fault.

The tectonic phase that established the NSR predated the deposition of units 1- 4 that fill the channel, meaning that it is older than 200 ka. This alluvial/colluvial sequence fills a paleo-channel that flows northward between the slopes of Mt. Carmel in the west and the rock barrier of the shutter ridge in the east. The total thickness of the alluvial-colluvial fill is unknown since the buried bed rock was not exposed in the trench. However, the lower indurate gravel unit, which underlies unit 4, might represent the gravel pavement of the paleo-channel bottom. Therefore, the thickness of the alluvial/colluvial fill can be estimated as 7-8 m.

The indurate gravel unit at the base of the trench is separated from the overlying friable fill of unit 4 by a clear contact, which suggests a depositional hiatus associated with a major change in depositional environments.

Most of the channel is filled by unit 4, which is dominated by clay. The age of this unit ranges between 200 ka and 100 ka, reflecting a slow accumulation rate, which lasted several tens of thousands years. The massive structure and the lack of stratigraphic features might be a result of a low sedimentation rate accompanied by intensive bioturbation. Nevertheless, it might also be related to the annual reaction (shrinking and swelling) of the clay to wet and dry seasons, which can erase any evidence of a sedimentary structure in the sequence.

The two facies of unit 4 (4a and 4b), which are separated by a sub-vertical unclear boundary, reflect two different sediment sources. The western fine-clastic vertisol facies was probably contributed by the near slope of Mt. Carmel. The rare coarse gravel in this unit suggests stable slopes, probably mantled with reddish-brown soils and covered by dense vegetation. The large disorthic, leached carbonate nodules scattered among this sequence are remnants of calcic soils that were disrupted by the continuous shrinking swelling process of the clay.

The northern coarse facies (unit 4a) is dominated by very coarse gravel (up to 70 cm), embedded in a clay matrix, which points to a possible debris flow and/or alluvial mass transport events as the main sedimentary agents. The lithology of the coarse gravel, especially the yellow and white sandy dolomites gravel, suggests a source that is not the near slopes of the Carmel. Therefore, it is assumed that the sediment fluxes originated from colluvium aprons on remote slopes of the Carmel. This coarse sediment was transported to the shutter ridge barrier by the north and northwest flowing first order streams that converge near the shutter ridge. The sediment fluxes were deflected northward by the rock barrier, which forced them towards and along the western wall of the barrier, and therefore, they were deposited near the shutter ridge. The similar ages of the course and the fine-clastic facies of unit 4 delineate the contiguous deposition of the two facies across the back-barrier channel.

Although there is no evidence for syn or post-depositional deformation in unit 4, it should be emphasized that in such clay dominated sediments tectonic features are rarely preserved.

The polygenetic soil at the top of unit 4, which includes a stage II calcic soil and relicts of older, well-developed calcic soil, indicates a long period of stability of the surface of the terrace combined with pedogenesis and minor erosion. This surface was later covered by the younger colluvial units 5 and 6.

It is not clear what the paleogeographic change that caused the transition from a continuous fluvial activity in open channel to slow accumulation of the slope sediments of unit 4 was. However, this process led to a complete filling of the back-barrier channel and incision of a new outlet by the stream at the southern margins of the back-barrier terrace. The small, W-E oriented right lateral strike slip fault that bounds the new outlet might suggest the involvement of tectonic activity in determining its location. The eroded surface at the top of unit 4 was probably established when the stream returned to an eastward course by breaching the barrier. Therefore, it represents a time gap that lasted until a new colluvial apron from units 5 and 6 were deposited on the abandoned terrace. Unit 5 covers all of back-barrier terraces, forming a continuous, un-deformed colluvial apron. There is no absolute age for this unit, but it is clear that it post-dates unit 4, which is at least 100 ka old. However, there is no clear soil profile in this unit, indicating that it is probably of late Pleistocene age.

In summary, the main tectonic phase that formed the NSR is of Late-Middle Pleistocene or early Late Pleistocene age. If there was any tectonic activity during the deposition of unit 4, its evidence was erased by the clay shrinking-swelling process. The young colluvial unit seems to be un-deformed.

Other neotectonic studies along the Yagur fault system

Introduction

Three sites were investigated along the Yagur fault in the last years. The depositional history of sediments that accumulated beyond two shutter ridges were analyzed in order to reconstruct their tectonic history, and a paleoseismic study was carried out in a trench excavated across the trace of the Nesher fault, a branch of the Yagur fault (Zilberman et al., 2006, 2009). The young (post Miocene) vertical uplift of Mt. Carmel was investigated in the Nesher Quarry (Zilberman, 2010). The main results of the previous studies are presented below.

The Nesher fault

The Nesher fault is a short, E-W oriented branch of the Yagur fault, which splits from the main stem south of Nesher. The vertical displacement of this fault declines from 1000 m near the splitting point from the Yagur fault in the east to a few meters in the water divide of Mt. Carmel, some 5 km to the west (Kcartz, 1959). Most of the vertical offset predated the Pliocene (Zilberman et al., 2010), and the young tectonic activity is dominated by a strike-slip movement (Zilberman et al., 2006; 2008).

The paleoseismic study was performed near the splitting point of the Nesher fault from the Yagur fault, assuming that each major seismic event that occurred along the Yagur fault reactivated the Nesher fault. This means that the paleoseismic record of the Nesher fault represents only major seismic events on the Yagur fault and not all of the tectonic activity.

This paleoseismic research found evidence for tectonic subsidence of a small depression south of the fault trace. The subsidence is at least 178 ±20 ky old (the base of the alluvial fill was not exposed) and it continued to subside slowly up to almost 20 ka. Discrete seismic events could not be detected in the sequence attached to the fault, but it is clear that this fault was episodically reactivated during the entire late Pleistocene. The upper time-limit for the tectonic activity was determined at 20-27ka because the younger upper part of the sequence was disturbed by anthropogenic activity.

The Southern Shutter Ridge

The Southern Shutter Ridge developed along the N-S oriented segment of the Yagur fault that extends between Yoqneam in the south and the A'amaqim Junction (Jalame) in the north (Ashkar-Halak, 2009). The sequence that was accumulated beyond the barrier was analyzed by Zilberman et al., (2006, 2008). Two periods of sediment accumulation were identified in this sequence: A slow deposition of an alluvial unit rich in weathered pyroclastic fragments (from unknown outcrops of volcanic rocks) started 140±20 ky ago, and terminated before 25 ka, when the barrier was probably breached and the stream incised at least to its present level. This incision was followed by a rapid accumulation of an almost 8 m thick alluvial and colluvial sequence of middle Holocene ( ≥5000 Y.B.P.) age, consisting of eroded soils and carbonate gravels of local origin with no volcanic components. The present incision of the stream in this young fill is younger than 2000 Y.

The accumulation of sediments in this steep gradient stream is attributed to a complete or partial blocking of the stream outlet. This process might be related to the left lateral offset of the shutter ridge, and thus reflects a phase of intensive tectonic activity. Another option, which cannot be ignored, is that there was a massive debris flow that blocked the stream outlet, or a climatic change impacted the balance between the contribution of run off and sediments to the stream. However, no evidence to such events was found in the study site.

The analysis of this shutter ridge sequence indicates continuous, but slow tectonic activity that lasted during most of the late Pleistocene and maybe also a short but intensive tectonic phase that occurred during the Middle Holocene.

The Nesher Quarry

The Nesher Quarry, exploited by the cement industry, is a submarine channel filled by a sub-horizontal sequence of marine gravity mass-flow sediments. The sequence, more than 60 m thick, was deposited in the margins of the Zevulun Valley during the Messinian and the lower Pliocene at a depth of at least 300 m. It was uplifted to the present altitude (20-90 m) after the lower Pliocene (Zilberman et al., 2010a).

The post Early Pliocene vertical uplift of the Carmel was not induced by tectonic activity along the Yagur fault, but it is part of a regional uplift of the entire mountainous back bone of Israel extending between the Be'er Sheva Valley in the south and the Yisrael Valley in the north. The Yagur fault only serves as a tectonic boundary that enabled this uplift by separating between the southern mountainous block and the northern densely faulted tectonic province of the Yizre'el and Zevulun valleys and the Lower Galilee (Zilberman et al., 2010b).

Additional Data


Fig. 11

Evidence for tectonic activity along the Yagur fault during the late Pleistocene and the Holocene. The last 13 ka are marked in yellow.

Zilberman et al. (2011)


Several studies suggesting Pleistocene and Holocene tectonic activity along the Yagur fault have been published in the last years (Fig. 11).
  1. A vertical displacement of about ten meters was detected in the subsurface trace of the Yagur fault near Nesher. The displaced units are about 50 ky old (Salamon, 2000).

  2. A small displacement of a 30 ka alluvial unit was described by Gluck (2002) in a small alluvial fan that covers the Yagur fault trace near Kibbutz Yagur.

  3. Several episodes of destruction, some of them are assumed to have been induced by earthquakes, were described from Megido ruins by Marco et al., (2006). It was suggested (although with no clear evidence) that some of these seismic events originated at the Yagur fault.

  4. A study of clusters of broken speleothems in Denya Cave, located only 4 km from the Yagur fault (Braun, 2009), suggest that each of them is related to a strong ground acceleration induced by a seismic event. Two of these clusters were dated to the Holocene circa 10ka and 5ka.
Although the sources of the seismic events that produced the ground acceleration that broke the speleotems were not determined, it is worth noting that all the strong earthquakes that occurred along the Dead Sea Rift Valley in the last 5000 yrs (up to M=7.4-7.6; Ambraseys, 2009 and refer. therein; Kagan et al., 2011; and refer. therein), did not cause any damage in the cave. This might suggest that remote earthquakes, although very strong, can not produce ground acceleration strong enough to break the speleotems in this area and the damages in the cave represent mainly earthquakes with close epicenters located on the Yagur fault.

References
References

Articles and Books

Ashkar-Halak, L., Greenbaum, N., Salamon, A., Zilberman, E., 2006. Morphologic and morphotectonic elements along the eastern and northeastern Carmel Mountain front – evidence for young tectonic activity . Isr. Geol. Soc. Ann. Meet. Bet Shean, abstract, p. 6.

Braun, Y. (2009). Dating Paleo-seismic Activity on the Carmel Fault Using Damaged Cave Deposits from Denya Cave. Msc. Thesis Hebrew University of Jerusalem

Braun, Y., et al. (2009). "Dating speleoseismites near the Dead Sea Transform and the Carmel Fault: Clues to coupling of a plate boundary and its branch." Israel Journal of Earth Sciences 58: 257-273.

Shamir, G. (2007). Earthquake epicenter distribution and mechanisms in northern Israel : Geological Survey of Israel. Report GSI/16/2007. in Hebrew

Zilberman, E., Greenbaum, N., Nahmias, Y., Porat, N., Ashkar, L., (2007). Middle Pleistocene to Holocene Tectonic Activity along the Carmel Fault – Preliminary Results of a Paleoseismic Study , .Isr. Geol. Surv. Rep. GSI/02/2007, 35 pp.

Zilberman, E., Greenbaum, N., Nahmias, Y., Porat, N., Ashkar, L. (2008). Late Pleistocene to Holocene tectonic activity along the Nesher fault, Mount Carmel, Israel . Israel J. Earth Sci. 57: 87-100.

Zilberman, Ezra, N. G., Yoav Nahmias, Neomi Porat (2011). The evolution of the Northern Shutter Ridge, Mt. Carmel, and its implications on the tectonic activity along the Yagur fault. GEOLOGICAL SURVEY OF ISRAEL. Jerusalem, Israel,

Wikipedia Pages

Shutter Ridge