انجمن کواترنری ایران دو فصلنامه کواترنری ایران 2423-7108 8 3 و 4 2023 02 20 Relationship between Climate change and destroy civilization Shahre soukhte by Investigating the Hamoun deposits ارتباط تغییرات اقلیمی و افول تمدن شهر سوخته با بررسی نهشته‌های بستر هامون 477 506 705269 10.22034/irqua.2023.2004059.1001 FA جواد درویشی خاتونی دکترای ژئومورفولوژی، دانشکده جغرافیا و برنامه ریزی محیطی، دانشگاه سیستان و بلوچستان، زاهدان، ایران صمد فتوحی دانشکده جغرافیا و برنامه‏ ریزی محیطی، دانشگاه سیستان و بلوچستان، زاهدان، ایران حسین نگارش دانشکده جغرافیا و برنامه‏ ریزی محیطی، دانشگاه سیستان و بلوچستان، زاهدان، ایران مقصود بیات دانشکده جغرافیا و برنامه‏ ریزی محیطی، دانشگاه سیستان و بلوچستان، زاهدان، ایران Journal Article 2023 06 05 Introduction The subject of paleoclimatology has various aspects of study importance, one of these aspects is in the field of archaeological studies. Archaeologists need accurate and clear information about the environmental and climatic conditions of that region in the past to understand the development of cultures and the rise and fall of civilizations. Lakes provide high-sensitivity and high-resolution documents and evidence, which are required for studying climatic changes and sedimentary environments at the global level. Furthermore, aeolian deposits in lacustrine environments, because of recording drought periods and dust storms, are valuable archives of paleoenvironmental conditions. In this research, to investigate Hamoun as an important water source in the southeast region of Iran, to discover the relationship between climate conditions and several thousand years old civilization in the Shahre-sokhte. Meterials and Methods In the present study, besides collecting the previous data, it was attempted to sample three intact sedimentary cores with the maximum depth of 7.3 m and total depth of above 20 m, from the sediments of the lakebed by auger. Sedimentary facies were separated based on their color, grain size; sedimentary composition, grain shape, and type of evaporate minerals. Results Regarding the percentage of the particles existing in the sediments of Hamun's bed (depth of up to 7 m), the sediment types were determined in accordance with their frequencies as follows: slightly gravelly sandy mud, sandy mud, sand, slightly gravelly sand, muddy sand, mud, gravelly mud, muddy sandy gravel, sandy silt, silty clay, and clay. Sorting the aeolian sediments was obtained through IGSD equal to 0.75, which was located in the moderate-to-good range. The average skewness in sediments of the taken cores was 0.15, which indicated skewness toward very fine particles. Also, the average kurtosis for the sample taken from pneumatic sand zones was equal to 1.3 (kurtic). The variations in the values of the parameters of some of the samples were due to the combination of different aquatic and aeolian processes in some parts of the sandy zones. Furthermore, the presence of the sediments with moderate to good sorting as well as kurtosis and skewness toward the very fine-grained particles indicated the supply of sediments mainly with aeolian origin and, in some cases, with fluvial origin. Discussion As previously mentioned, activity of the dominant winds of the region is from north toward northwest. Existence of the heights in the west of Hamun, which sometimes reaches 1700m, acts as an obstacle against the dominant winds. In this regard, existence of Rudbandan Valley can act as a channel for the passage of the winds, and reinforce and channelize the winds. This factor can also justify the high thickness of the aeolian sediments at the crater of Rudbandan delta (core H-2). Another effective factor is the feeding of Helmand and Sabari hamuns by rivers of the drainage basin (Helmand and Farah rivers). The sediments of Hamun's lakebed demonstrate the dominance of the aquatic facies; however, such conditions are more prominent for Hamun-e-Helmand due to the great area of the drainage basin and high water volume of Helmand River. Therefore, we can see the alternation of the lacustrine facies (with dominant thickness), fluvial facies (sediments of river channel), and aeolian facies in the core H-3, which are reduced along the sediments toward the cores H-1 and H-2 and is gradually converted into the marginal lacustrine and fluvial (mainly floodplain) as well as aeolian environments (especially in the core H-2). In the core H-2, due to the low area of the drainage basin of Rudbandan, low sedimentary input, and high intensity of the dominant winds, the aeolian sediments are dominant. It seems that the sedimentation rate in the late-Holocene drought period has been very high due to the high volume of the aeolian sediments, or probably no intense erosion has occurred after the sedimentation. In other words, after the drought 4.5 ka BP in Hamun, no intense drought with severe erosion has occurred. The windiness conditions of the region in the late-Holocene have been comparable to the current 120-day winds. However, the case is different for the aeolian sediments found at the depth of 4.5 m, which is equivalent to the drought event of 800 BP and has coarser grains and less thickness. It seems that, due to the high intensity, the power of carrying has been very high, and probably again influenced by erosion after the sedimentation so that a part of the sediments has been re-carried while leaving slight thickness (40 cm). The presence of the sequence of aeolian sediments and lack of plant and animal relicts imply the complete drying of the lakebed in a certain period so that, in this period, sedimentation of the aeolian deposits has been catastrophically concordant with the sedimentation of the silty and muddy deposits of the floodplain sediments. The existence of brown-colored coarse-grained pneumatic sand particles during the early to mid-Holocene period (8.2 ka BP) indicated the occurrence of intense storms in Sistan Basin. Sequence of the fine- and very fine-grained pneumatic sands at the depth of 2.5 m represented the presence of the winds similar to the current "120-day winds" in Sistan plain. Moreover, in this study, two major drought periods (8.2 and 4.5 ka BP) were identified in Holocene sediments of the lakebeds of Hamun-e-Helmand and Hamun-e-Sabari, which indicated drying and expansion of the aeolian sediments on Hamun's lakebed. The subject of paleoclimatology has various aspects of study importance, one of these aspects is in the field of archaeological studies. Archaeologists need accurate and clear information about the environmental and climatic conditions of that region in the past in order to better understand the development of cultures and the rise and fall of civilizations. One of the important issues in this regard is the role of environmental changes over time and its impact on human livelihood and settlement. The decline of the ancient civilization of the burnt city, it shows a good correspondence with the dry period 4500 years ago. Which lasted about 500 to 700 years. در این پژوهش به بررسی رسوبات بستر هامون و ارتباط شرایط آب و هوا با افول تمدن چند هزارساله منطقه در شهر سوخته پرداخته شده است. در این مطالعه اقدام به برداشت 3 مغزه رسوبی به صورت دست نخورده از رسوبات بستر دریاچه توسط مغزه‌گیر اوگر شد. با توجه به تغییر رخساره‌های رسوبی از سطح به عمق و نتایج آنالیز دانه بندی و مورفوسکوپی، تفکیک محیط‌های بادی، دریاچه ای و آبرفتی انجام گرفت و در نهایت جغرافیای عملکرد بادهای دیرینه و رسوبات بادی بازسازی گردید. با توجه نتایج سنسنجی حمزه و همکاران (2013)، وجود ذرات درشت ماسه بادی در اوایل تا اواسط هولوسن (8200 سال قبل) نشانگر وزش توفان‌های شدید در حوضۀ است. توالی ماسه های بادی دانه ریز و بسیار ریز در عمق حدودی 5/2 نشان دهنده وجود بادهای مشابه با بادهای 120 روزه فعلی سیستان می باشد. دو دوره مهم خشک (8200 و 4500 سال پیش) در رسوبات هولوسن بستر هامون های هیرمند و صابوری شناسایی گردید که حاکی از خشک شدن و گسترش رسوبات بادی است. افول تمدن باستانی شهر سوخته، از نظر زمانی انطباق مناسبی با دوره خشک 4500 سال پیش، که حدود 500 تا 700 سال طول کشیده است، نشان می دهد.

https://www.iranquaternary.ir/article_705269_8401985bbc4c985b4c6cd1a36fae62ab.pdf