Lake Maryut (northwestern Nile Delta, Egypt) was a key feature of Alexandria's hinterland and economy during Greco-Roman times. Its shores accommodated major economic centers, and the lake acted as a gateway between the Nile valley and the Mediterranean. It is suggested that lake-level changes, connections with the Nile and the sea, and possible high-energy events considerably shaped the human occupation history of the Maryut. To reconstruct Lake Maryut hydrology in historical times, we used faunal remains, geochemistry (Sr isotopic signature of ostracods) and geoarcheological indicators of relative lake-level changes. The data show both a rise in Nile inputs to the basin during the first millennia BCE and CE and a lake-level rise of ca. 1.5 m during the Roman period. A high-energy deposit, inferred from reworked radiocarbon dates, may explain an enigmatic sedimentary hiatus previously attested to in Maryut's chronostratigraphy.
In griechisch-römischer Zeit spielte der Maryut-See (nordwestliches
Nil-Delta, Ägypten) eine wirtschaftliche Schlüsselrolle im
Hinterland von Alexandria. An seinen Ufern befanden sich wichtige
Wirtschaftszentren und der See fungierte als Bindeglied zwischen dem Niltal
und dem Mittelmeer. Es ist zu vermuten, dass Schwankungen des Seespiegels,
Verbindungen zum Nil und zum Mittelmeer und mögliche
Hochenergieereignisse die menschliche Besiedlungsgeschichte des Maryut-Sees
beachtlich geprägt haben. Um die Hydrologie des Maryut-Sees in
historischer Zeit zu rekonstruieren, untersucht diese Studie Faunenreste,
geochemische (Sr-Isotopensignaturen von Ostrakoden) und
geoarchäologische Indikatoren, die relative Schwankungen des Seespiegels
anzeigen. Die Ergebnisse zeigen sowohl einen Anstieg der Nileinträge in
den See während des ersten Jahrtausends v. Chr. und n. Chr. als auch
einen Anstieg des Seespiegels um ca. 1,5 m während der Römerzeit.
Ein Hochenergieereignis, ausgewiesen durch umgelagerte
Lake Mareotis, precursor of the modern Maryut lagoon located just south of Alexandria (Egypt), constituted a dense traffic waterway during antiquity (Empereur, 1998), straddling the northwestern Nile Delta. Extensive archeological surveys have shed new light on the intense occupation of its shores between the 4th century BCE and the 7th century CE (Blue and Khalil, 2010). An archeological synthesis at the scale of the western delta has demonstrated that paleo-waterways and the overall hydraulic configuration shaped the geography of ancient settlements (Wilson, 2012). Our knowledge and representation of the ancient water network is primarily based upon historical statements, in particular Strabo (Strabo, XVII, 1, 7; translation Yoyotte et al., 1997), according to whom Lake Mareotis was connected to the Nile through several canals on its southern and eastern sides. Lake-level oscillations were then mediated by Nile floods. Nonetheless, this vision furnishes a static view of the lake, whose shores were occupied for a period of 1000 years or more, as recently underscored at Kom el-Nogous close to Taposiris Magna (Fig. 1), occupied during the New Kingdom (Redon et al., 2017). Following Stanley (2019) quoting Butzer (1976, p. 56), “it has become difficult to ignore the possibility that major segments of ancient Egyptian history may be unintelligible without recourse to an ecological perspective.” We suggest that this statement resonates strongly with the human occupation history of Lake Mareotis, as originally perceived by De Cosson (1935).
Lake Mareotis is part of the coastal belt of the Nile Delta, spread over a structural boundary which separates Pleistocene coastal sandstone ridges to the west and northwest from the Holocene Nile Delta to the east and southeast (Fig. 1). This situation at the deltaic margin made it very sensitive to hydrological changes, modulated by Holocene relative sea-level changes (e.g., Goiran et al., 2018) and Nile flow modifications (e.g., Sun et al., 2019). We have previously exploited Lake Mareotis sedimentary archives in order to reconstruct its Holocene history (Flaux et al., 2011, 2012, 2013, 2017), aiming to elucidate the ancient geography and hydrology of the lake. The marine transgression of the area is dated to 7.5 ka cal BP. Nile inputs then became progressively predominant in Maryut's hydrology (7–5.5 ka cal BP) in the context of the African Humid Period (AHP). Between 5.5 and 2.8 ka cal BP, the end of the AHP is translated by a progressive hydrological shift from a Nile-dominated to a marine-dominated lagoon. A hiatus in Maryut's sedimentary record precludes investigating the lagoon system between 2.8 and 1.7 ka cal BP. The final phase from 1.7 to 0.2 ka cal BP was characterized by dominant freshwater inputs except between 1.1 to 0.7 ka cal BP, when a Maryut relative lowstand and seawater intrusion are attested. New bio-sedimentological, geochemical, radiocarbon and geoarcheological data have helped to shed new light on the evolution of Lake Mareotis' water budget during historical times. In particular, this paper aims to better constrain hydrological conditions of the lake during the Greco-Roman period and probe the sedimentary hiatus previously described within the lake sequence (Goodfriend and Stanley, 1996; Flaux et al., 2012).
This study is based on sedimentary sequences retrieved from archeological structures and Lake Maryut. All localities have been benchmarked relative to mean sea level (tide-gauge data from Alexandria taken in 1906) using a differential GPS.
Akadémia and Kôm de la Carrière are two Roman
archeological sites lying on the southwestern waterfront of Lake Maryut
(Fig. 1). At Akadémia, one sedimentary core was taken from a flooded
kiln chamber (core AKA19; 30
At Kôm de la Carrière eight sedimentary cores were collected
in 2015 from a ancient silted quarry (Fig. 2). Core AMR-3 (31
Kôm de la Carrière archeological site. Map
Radiocarbon data from the Kôm de la Carrière site (core AMR-3) and section M83. The
The stratigraphy of Maryut lagoon's southeastern basin was investigated
using the new sedimentary section M83, collected in 2014 from the section of
a drain crossing the former lagoon bottoms, now cultivated (Fig. 1;
31
Sr isotope data from the ostracod
The Kôm de la Carrière site is located on the southwestern shore of Lake Maryut (Fig. 1) at the foothill of a Pleistocene ridge mostly made of poorly consolidated aeolian oolitic carbonate sands (Gebel Maryut ridge; El Asmar and Wood, 2000). This bedrock has been carved in the form of a box-shaped quarry opening onto Lake Maryut (Fig. 2), which led El-Fakharani (1991) to suggest that this structure was later used as a protected harbor in ancient times. Core AMR-3 was taken from the silted quarry in order to test this hypothesis. Three main units were elucidated along the sedimentary sequence.
Unit A is composed of light gray silts and clays (56 %). The sand and
gravel fractions respectively represent 17 % and 27 % of the sediment
texture. The ostracods comprise an association of freshwater to brackish
(86 %) and lagoonal (14 %) species.
Unit B comprises 63 % silts and clays, 17 % sands, and 20 % gravels.
The gravels fraction is dominated by ceramic fragments. There is no color
change in relation to unit A. The unit is dated between 370–175 cal BCE and
775–1200 cal CE (1050
The study of the ostracods allowed us to divide unit B into two subunits.
Subunit B1 shows a high density of ostracods (between 530 and 4800 valves
for 10 g of sediment). The ecology shows that lagoonal (
Unit C is sandier (27 %), but silts and clays still dominate the total
texture (70 %). The gravels represent (3 %) of the sediment aggregate.
The faunal density is very low with a maximum density of around 75 valves
for 10 g of sediment in the middle of the unit.
Akadémia is located on the southwestern shore of Lake Maryut, close
to the ancient site of Marea-Philoxenite, ca. 8 km southwest of
Kôm de la Carrière (Fig. 1) on the piedmont of the same Gebel
Maryut Pleistocene ridge. Archeological remains at Akadémia are
composed of an amphora workshop (kilns, activity level and a big waste
dump) and a wine press from the 2nd century CE and hydraulic
structures from the 5th to early 7th century CE. The plan view
of one of the amphora kilns shows a semi-buried circular structure 12.65 m
in outside diameter and 7.7 m in inside diameter. The firing chamber of the
amphora kiln was cored in order to probe its volume and infilling (core
AKA19; Fig. 3). The base of the firing chamber was found 4 m below the oven
floor at 0.6 m below msl (mean sea level). The first deposit is a composite, comprising
eight layers, 0.1 to 10 cm thick, of ashen and char sediments intercalated
with silty sands and fragments of fired clay bricks. This first deposit
translates the kiln activity. It is mainly overlain by fragments of fired
clay bricks within a sandy silt matrix, related to the abandonment and the
infilling stage of the structure. Four well-defined layers of clayey silts,
5–10 cm thick and including a few specimens of the freshwater ostracod
Akadémia archeological site.
Core AKA12 retrieved the infilling of a sakieh well found on the western part of
Akadémia and is dated to the 5th to early 7th centuries CE (Fig. 3). The sequence is 3.8 m thick. At the base, unit A is made of alternating
fine to coarse oolitic sand layers, including a few shell fragments and
aeolianite gravels corresponding to the upper altered bedrock. The first
depositional layer in the well comprises hydromorphic clayey sandy silts
(unit B) with a few specimens of the freshwater ostracod
The upper unit A comprises an alternation of shell-rich and dark mud layers
deposited at the centimetric scale. Shell-rich layers comprise very abundant
shell fragments and well-preserved and abundant gastropods, mollusks and
ostracod valves, the latter sometimes still in connection. Species density
is high and diversity low, dominated by
Unit B is 0.8 m thick and comprises homogeneous silty clays (90 %–95 % of
the bulk sediment), dark gray to brown, with a lumpy structure. Gypsum
dominates the composition of the sand fraction mainly in discoidal
lenticular forms. In sectional view, fine white gypsum was observed in the form of
nodules and a mycelium-like morphology. Macrofauna and microfauna are scarce
in this unit, but nonetheless the gastropods
Multi-proxy analysis of section M83 taken from southeastern
Lake Maryut (Fig. 1). The mass fraction of seawater was estimated via a
two-component mixing equation using modern seawater and Nile river water
The next unit C comprises compact dark gray clayey silts with a lumpy
structure. There is a rich gypsum layer with a pseudo-mycelium structure.
Macrofauna density remains are just a few individuals per 100 g of dry
sediment, although it peaks to
Radiocarbon data from units B and C show great inconsistency (Fig. 4). Three
samples, taken from the base of unit B, display ages ranging from 900 BCE to
950 CE. A shell from the middle of unit B was dated to 760–420 BCE, while a
burnt bone taken from the same level dates to late Pleistocene times
(
The lower and upper interfaces of unit D were sharply defined. The facies
shows an increase in fine-sand inputs that reach ca. 50 % of the
sediment bulk. Sands are dominated by quartz minerals. A laminated structure
is partially preserved with alternations of sand-rich and mud-rich
infra-millimetric layers. The faunal assemblage is characterized by the
return of lagoonal species sensu stricto and an increase in
Unit E provides the last record of section M83. The sand fraction, dominated
by quartz minerals, decreases to 25 %–50 % in the lower half and 10 %–25 %
in the upper part. The unit contains a few individuals of lagoonal shells
(
Mixed sediments deposited in section M83 have nevertheless recorded,
according to fauna and
At Akadémia, the kiln and the sakieh lie 500 m from each other in
a similar geomorphological context at the foothill of a Pleistocene coastal
ridge covered by late Quaternary aeolian sands (El-Asmar and Wood, 2000)
ca. 150 m from the modern Lake Maryut shoreline. The base of the kiln's
firing chamber lies at a similar depth to the base of the sakieh well, suggesting
a rise in the water table between the 2nd (kiln activity) and the
5th to early 7th (sakieh activity) centuries CE, which is in accordance with
clayey silt layers including a few specimens of the freshwater ostracod
The study at Kôm de la Carrière has revealed that the quarry was
excavated before or at the beginning of the Hellenistic period at a time
when the level of the lake was below mean sea level (msl), given that it is
not possible to extract the stones below shallow water (Fig. 2). Following a
subsequent rise in water level, the quarry was transformed into a
lightly brackish to freshwater basin connected to Lake Mareotis (unit A) and maybe used
as a protected harbor. Alternatively, the quarry could have been excavated
while disconnected from the lake before the excavation of a canal towards
the lake. However, the great porosity of the bedrock, made of poorly
consolidated fine to coarse sand layers, and the proximity of the lake go
against this hypothesis. Our chronological framework shows that the onset of
sedimentation is not much earlier than 370–195 cal years BCE (terminus post quem), which is consistent
with excavations and archeological surveys undertaken upon the adjacent
Kôm, showing an occupation spanning the Greco-Roman period (Pichot,
2017). Moreover, the basin silted during or after the late Roman period and
later, as suggested by late Roman sherds discovered in most of the cores
drilled into the silted quarry. Ostracod assemblages from this silting stage
(units B1 and B2) comprise 25 % freshwater (
Geoarcheological indicators therefore suggest that (1) Lake Mareotis was a lightly brackish lagoon and (2) its level increased by at least ca. 1.5 m between the 2nd and the 5th centuries CE and lay above msl. Late Pleistocene stiff muds lying below Holocene sediments (Chen and Stanley, 1993) represent a relatively impermeable substratum that could have favored the water-level rise and stabilization above msl. It is not clear, however, whether the lake level stabilized above msl or was a seasonal high level linked to the Nile flood. More data are required to better document the dating and nature of this hydrological change, which is crucial for the interpretation of lakeshore archeological sites. For example, the lake-level rise could partially explain the apparent abandonment of Lake Mareotis' southwestern waterfront during the 3rd–4th centuries CE (Pichot, 2017).
M83 chronological framework records a mixed sediment layer (units B and C)
deposited between two non-reworked laminated facies (units A and D). The
lower unit A is composed of shell-rich layers with a marine
According to historical sources, eight tsunamis or high-energy marine events struck the coast of Alexandria during antiquity (Goiran, 2012). Previous research has focused on their sedimentological signatures in cores from Alexandria's ancient maritime harbors. Goiran et al. (2005) identified a coarse deposit with older reworked dates, mixed fauna and coarse sediment inputs, including shock impacts on quartz grains (Goiran, 2012). Radiocarbon dates framing the coarse deposit suggest that it has recorded the tsunami wave that hit Alexandria in 811 or 881 CE (Goiran, 2012). Stanley and Bernasconi (2006) observed a possible tsunamite facies with mixed fauna and slump-like sediment strata. Overall, both studies identified, in several coastal sequences of Alexandria's eastern harbor, a centennial- to millennial-scale sedimentary hiatus, as in some of the Lake Mareotis' sequences. It remains, however, difficult to link ancient processes to missing sediments. In Lake Mareotis, section M83 may have recorded mixed sediment reworked from the lake bottoms. The younger reworked age is chronologically consistent with the high-energy event, providing a terminus post quem to 700–950 cal CE. In core M12, given that the gypsum-rich layer following the sedimentary hiatus was dated between the 9th and the 12th centuries CE (Flaux et al., 2012), the 811 or 881 CE tsunami wave may have impacted not only Alexandria's coastal waterfront (Goiran, 2012) but also its southern lakeside. In section M3, however, the sedimentary hiatus spans a shorter period, up to the 2nd–3rd centuries CE, meaning that an older tsunami would have eroded these lake bottoms. Three tsunamic layers deposited during the last 2000 years were found within coastal lagoons protected by 2–20 m high dunes on the northwestern coast of Egypt (Salama et al., 2018).
Alternatively, recurrent gypsum in pseudo-mycelium form observed in units B and C, as well as their lumpy sediment structure and dark color likely related to higher organic input, suggests the development of pedogenic features at site M83. Soil development would necessarily imply that Lake Mareotis retreated from this area and would likely derive from the lake-level lowstand previously recorded after evaporitic deposits in sequences M3 and M12 between the 9th to the 12th centuries CE (Flaux et al., 2012). Soil biological activity or agricultural plowing could also explain reworking dating along units B and C. Although this alternative hypothesis does not explain the enigmatic sedimentary hiatus recorded from the deeper part of the lake, it shows that the tsunami hypothesis requires deeper investigation. Synolakis and Fryer (2001) and Marriner et al. (2017) caution that every coastal enigma does not necessarily have a tsunami explanation.
Lake Mareotis was densely occupied during Greco-Roman times. The present contribution aims to better constrain hydrological conditions of the lake during this period. Faunal remains, the Sr isotopic signature of ostracods and geoarcheological indicators of lake levels show both a rise in Nile inputs to the basin during the first millennia BCE and CE and a lake-level rise of ca. 1.5 m during the Roman period. Such changes highlight a complex co-evolution of Alexandria's lakeside occupation history and Nile flow changes, the latter being divided into fluctuating distributaries at the delta scale that were furthermore diverted by irrigation and drainage networks (e.g., Blouin, 2006). From a forward-looking viewpoint, the Alexandria canal (see location in Fig. 1) may have played a crucial role in the evolution of Lake Mareotis' water budget: (1) it has partially diverted the Canopic Nile flow towards the delta's western margin, and (2) it has disconnected the lake from the Aboukir lagoon and thus from the sea, favoring Lake Mareotis' desalinization and allowing its level to rise above msl, as observed at Akadémia and Kôm de la Carrière archeological sites. In any case, desalinization of the northwestern Nile Delta margin could have been key in the development of human occupation in this area during the first millennium BCE. At this time, Lake Mareotis became the natural conveyor for drainage and irrigation water. Since the Hellenistic period at least, there was increasing management of the water system around Lake Mareotis, a process which was accelerated during the Roman period (Pichot, 2017) and may have played a significant role in driving lake-level changes.
Lake Mareotis' configuration was transformed by the 9th century CE from a high-level, hypohaline coastal lake to a sebkha. While we previously related this environmental change to the progressive silting up of the Canopic branch and northwestern delta irrigation system, our new results instead highlight an environmental change related to the impact of possible high-energy event(s). A reconstruction of Lake Mareotis history requires new approaches and perspectives (Crépy and Boussac, 2021).
All data generated during this study are included in this article or are available from the corresponding author upon request.
CF, MG, VP, NM, MeA, AG, PD, CC and CM conceived the study and wrote the paper. CF, VP, NM, CM and MeA performed fieldwork and provided chronostratigraphies. MG performed ostracod analyses. CF, AB, PP and CC performed Sr isotopes analyses.
The authors declare that they have no conflict of interest.
This article is part of the special issue “Geoarchaeology of the Nile Delta”. It is not associated with a conference.
We thank Hélène Mariot for taking care of CEREGE's clean lab. Matthieu Giaime acknowledges the support of the Institute of Advanced Studies and the Department of Geography at Durham University. We thank two anonymous referees for constructive comments on an earlier version of the manuscript. We thank Martin Seeliger for kindly translating the abstract into German.
This research has been supported by the ANR (France) (grant no. ANR-12-SENV-0008-03), the Investissement d'Avenir (France) (grant no. EQUIPEX ASTER-CEREGE), and the Durham Junior Research Fellowship (grant no. 609412).
This paper was edited by Julia Meister and reviewed by two anonymous referees.